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Research Report Series No. 9 Alabama Agricultural Experiment Station Auburn University Lowell T. Frobish, Director March 1994
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PREFACE
Management practices, such as rotations, fertilizer applications, seeding dates and rates, insect and
disease control, and predicting the need for pest control, greatly influence profitability associated with
peanut production. Over the years, many studies dealing with the relationships between management
practices and peanut yield have been conducted. Detailed information from some of these studies has been
printed in various publications. The objective of this publication is to briefly summarize data from some
of these studies and to consolidate the information into a single publication. Additional information from
most of these studies can be obtained by contacting the researchers listed at the beginning of each article.
The articles have been grouped into six categories - rotations; fertility; planting dates, seeding rates,
and seed quality; diseases; insects; and models and prediction aids. Due to the nature of the research and
treatments involved, some articles could have been placed in other categories, and as a result, information
on a specific topic may be found in more than one category.
Mention of trade names does not indicate endorsement by the Alabama Agricultural Experiment Station or
Auburn University of one brand over another. Any use of pesticide rates in excess of labeled amounts in research
reported does not constitute recommendation of such rate Such use is simply part of the scientific investigation
necessary to evaluate various materials. No chemical should be used at rates above those permitted by the label.
iii
CONTENTS
Page
ROTATIONSe................................. .
. ..
Peanut-Corn Rotations....................................................5
Rotations with Cotton and Bahiagrass for Management of Root-Knot Nematodes in Florunner
Peanuts.........................................................5
Bahiagrass in Rotations Shows Promise for Boosting Peanut Yields.9
Potential Yield Increases from a New Fungicide for White Mold Control in Peanuts....... 11
Impact of Crop Rotation on Soilborne Diseases and Nematodes in Peanuts.................12
Peanut Economics.......................................................13
FERILITY....................................................6.15
Tillage, Subsoiling, Starter Fertilizer Combinations, and Starter Fertilizer
Placement Comparisons for Peanuts......................................... 
15
Calcium Requirements for Maximum Yield......................................016
Have We Been Overfertilizing Our Peanuts.?
9 . . . . . . . . . . . . . . . . . . . . . . . . . . .
.18
PLANTING DATES, SEEDING RATES, AND SEED QUALITY......................
Early Planting and Reduced Tillage Help Control Lesser Cornstalk Borer in Peanuts..........
Peanut Performance and Disease Occurrence as Influenced by Planter and Seeding Rate
Extra Calcium is Needed for Peanut Seed ......................................
DISEASES...........................................................
Application of Fungicides to Peanuts Through Irrigation Systems
Disease Reduced by Management of Southern Runner Peanuts
New Biological Seed Treatment Fungicide Increases Peanut Yields
SM-9 Spray Adjuvant and Control of Southern Stem Rot of Peanuts
Fungicide-Nematicide Seed Treatment Combinations: Results and Potentials.............
Peanut Foliar Fungicides: Relationships Between Leafspot Control and Kernel Quality........
Control of Peanut Soilborne Diseases May Afford Yield Breakthrough .. .. .. 
.. .. o.. .. .....
Viruses Infecting Peanuts.........................
INSECTS........................... 
...
Pheromone Traps Inadequate for Sampling Lesser Cornstalk Borer. ..........
Long-Lasting Granular Insecticide the Most Effective Against Lesser Cornstalk 
Borers.........
Why Are Lesser Cornstalk Borers a Hot and Dry Weather Pest of Alabama Peanuts
9
? 
. . . . . . . . .
Lesser Cornstalk Borer Damage to Peanuts .........................
Lesser Cornstalk Borer and Afiatoxins are Double Trouble for Peanut Growers.............
Granular Insecticides Harmful to Beneficial Insects in Peanuts .................
MODELS AND 
PREDICTION 
AIDS ...........................................
0 *
AU-Pnuts -- AAES Developed Expert System Helps Manage Peanut Pests 
..................
Weather Variables Aid in Predicting Abundance of Lesser Cornstalk Borer..................
Estimating Abundance of Lesser Cornstalk Borer Larvae One Week in Advance 
. ............ 0 0
19
19
S20
S23
025
25
926
028
929
&30
031
33
36
37
37
38
40
41
43
44
47
47
49
51
iv
FIRST PRINTING 4M, MARCH 1994
Information contained herein is available to all persons without regard
to race, color, sex, or natioal origin.
ROTATIONS
Peanut-Corn Rotations
J.T. Cope & J.G. Starling
Summarized by J.T. Touchton
A STUDY was conducted from 1965 through
1979 on a Dothan fine sandy loam soil at the
Wiregrass Substation in Headland, Alabama. The
primary objective was to evaluate time of
phosphorus (P) and potassium (K) fertilization for
both crops. Other than fertilizer variables,
production practices were the same for rotated and
continuously cropped peanuts.
Peanut yields (Table 1) are averaged over three
five-year periods. Over the years, peanut yields
steadily increased regardless of rotation. This
increase over time is attributed to improved
production practices, such as pesticides and
varieties. Although it took several years for the
rotation to result in relatively large yield increases,
these increases occurred at a time in which yields
of continuous peanuts were also increasing. The
effect of the rotation on corn yields were not as
dramatic as with peanuts. Over the 15-year period,
corn yields averaged 70 and 75 bu. per acre for
the continuous and rotated systems, respectively.
The economic analyses (Table 2) using the
average yield for the 1975-1979 period indicate
that the rotation was economically beneficial.
With current quotas and pricing system, the
rotation resulted in a net return (return to land,
quota, and management) of $153 per acre
compared to $52 for the continuous peanuts. The
$153 value includes a $51 per acre loss from the
corn crop. These results suggest that even if the
rotation limits peanut acreage, it is more profitable
to net $153 every other year ($76.50 per acre per
year) than $52 each year. In addition, the
potential for reduced production costs that a
rotation may provide, such as reduced needs for
pest and disease control, was not included in these
analyses.
Cope and Touchton, Department of Agronomy and
Soils; Starling, Wiregrass Substation.
TABLE 1. YIELD OF CONTINUOUSLY CROPPED PEANUTS AND
PEANUTS ROTATED WITH CORN
Year
Cropping
system 65-69 70-74 
75-79 65-79
----------- lb./acre--------------
Continuous ...... 1,390 2,040 2,510 1,980
Rotation .......... 1,620 2,590 3,060 2,420
(Difference) .... 230 550 550 440
TABLE 2. ECONOMIC COMPARISON OF CONTINUOUS AND
ROTATED PEANUTS WITH CURRENT SUPPORT SYSTEM AND
PRICE NEEDED TO BREAK EVEN WITHOUT QUOTA AND PRICE
SUPPORT SYSTEMS FOR THE 1975-79 AVERAGE YIELD DATA'
Net return ($/acre) Price needed ($/ton)
Cropping with current price to break even
System support without
price support
Continuous... 52 511
Rotation....... 153 453
'Net return and break even figures are return to land, quota,
and management. Calculations are based on the following
fixed figures: (1) a 2:1 ratio of quota to additionals; (2) a
quota value of $679 per ton and $300 per ton for additionals;
(3) a production cost of $642 per acre; and (4) a net loss of
$51 per acre for the corn crop rotated with peanuts. This net
loss was calculated from a 75 bu. per acre corn yield, valued
at $2.40 per bu., and a production cost of $231 per acre.
Rotations with Cotton and Bahiagrass for
Management of Root-Knot Nematodes in
Florunner Peanuts
R. Rodriguez-Kibana, H.W. Ivey,
D.G. Robertson, and L.W. Wells
DAMAGE caused by the southern root-knot
nematode is one of the principal yield-limiting
factors in peanuts in Alabama and other areas of
the southeastern United States. The nematode is
present in 40% of the peanut fields in Alabama,
[5]
and approximately 12% of the fields are so heavily
infested that production is not possible without
management of the pest. Traditionally,
management strategies for the nematode in the
southeastern United States have been based on the
use of nematicides and on rotation with crops that
are either nonhosts or that are poorer hosts than
peanuts. This management approach was
prompted by the decreasing availability of
inexpensive and effective nematicides such as
DBCP and EDB, which have been eliminated, and
by the lack of commercial peanut cultivars that are
resistant or tolerant to the nematode. Management
strategies based on crop rotations are at present the
only viable long-term solution to nematode
problems in peanuts. A number of crops have
been studied in rotation with peanuts for
suppression of root-knot problems.
The value of Deltapine 90 cotton in rotation
with Florunner peanut for the management of root-
knot nematode (Meloidogyne arenaria) and
southern blight (Sclerotium rolfsii) was studied for
six years.
Peanut yields (Table 1) following either one or
two years of cotton (C-P and C-C-P, respectively)
were higher than those of a peanut monoculture
without nematicide [P(-)]. At-plant application of
Temik? 15G to continuous peanuts [P(+)]
averaged 22.1% higher yields than those for P(-)
over the six years of the study. The use of the
nematicide in cotton and peanuts in the C-C-P
rotations increased yields of both crops over the
same rotations without nematicide. When Temik
was applied to both crops in the C-P rotation,
peanut yields were increased in only two of the
possible three years when peanuts were planted.
Application of the nematicide to cotton only in the
C-P rotation did not improve peanut yields over
those obtained with the rotation without
nematicide.
Juvenile populations of the nematode
determined at peanut harvest time were lowest
(Table 2) in plots with cotton. Plots with C-P or
C-C-P had lower populations of the nematode than
those in continuous peanuts with or without
nematicide treatment.
The incidence of southern blight (white mold)
in peanuts (Table 3) was lower in plots with the
rotations than in those with continuous peanuts.
Net economic return from the 1990 pcanut crop
based on current prices for support and world
market price peanuts showed (Table 4) a clear
economic advantage for the use of rotations over
the monoculture systems. Production of peanuts
using the monoculture system was not competitive
but was profitable with any of the rotation systems
studied.
The effect of Pensacola bahiagrass in rotation
with Florunner peanut on root-knot nematodes and
peanut yields has been studied since 1986 in a
field experiment. Peanut yields in plots following
bahiagrass were 27% higher than in plots under
continuous peanuts (Table 5). Each year soil
densities of second stage juveniles of the root-knot
nematode, determined near peanut harvest, were
96-98% lower under bahiagrass than under
peanuts; numbers of juveniles in plots with
bahiagrass-peanuts were 41% lower than in plots
with continuous peanuts. Using bahiagrass for
reducing population densities of root-knot
nematode was at least as effective as using Temik
at recommended rates for use in peanuts.
Rodriguez-Kibana and Robertson, Department of
Plant Pathology; Ivey and Wells, Wiregrass Substation.
[6]
TABLE 1. RELATION BETWEEN YIELDS OF PEANUT (P) AND OF COTrON (C) AND THE CROPPING SEQUENCE FOLLOWED IN AN EXPERIMENT AT THE
WIREGRASS SUBSTATION, HEADLAND, IN A FIELD INFESTED WITH MELOIDOGYNEAREARIA
Cropping sequence and year Yield (lb./acre)
1985 1986 1987 1988 1989 1990 1985 1986 1987 1988 1989 1990
P(-) P(-) P(-) P(-) P(-) P(-) 3,173 
2,929 1,383 1,899 2,061 1,546
P(+) P(+) P(+) P(+) P(+) P(+) 3,689 3,200 1,817 2,495 2,577 2,088
C(-) P(-) C(-) P(-) C(-) P(-) [2,794] 
3,499 [1,654] 1,573 1,573 2,235
C(+) P(-) C(+) P(-) C(+) P(-) [3,689] 3,499 
[2,061] 1,736 1,736 2,685
C(-) P(+) C(-) P(+) C(-) P(+) [2,821] 3,363 [1,790] 2,088 2,088 2,659
C(+) P(+) C(+) P(+) C(+) P(+) [3,083] 3,689 [2,088] 2,360 2,360 2,712
C(-) C(-) P(-) C(-) C(-) P(-) [2,875] [1,844] 2,088 [1,329] [1,329] 2,820
C(+) C(+) P(+) C(+) C(+) P(+) [3,445] [1,899] 2,495 [1,844] [1,980] 3,417
FLSD (P = 0.05): 489 409 336 404 469 507
[320] [377] [342] [478] [561]
' (-) = without nematicide; (+) = with at-plant application of Temik 15G at three lb. a.i. per acre row in an eight-in.-wide band.
2 Yield and FLSD values in brackets are 
for cotton; values without brackets are for peanuts.
TABLE 2. EFFECT OF CROPPING SYSTEMS WITH PEANUT (P) AND COTrON (C) ON END-OF-SEASON JUVENILE POPULATIONS OF MELOIDOGYNE
ARENARIA IN A FIELD EXPERIMENT AT THE WIREGRASS SUBSTATION, HEADLAND
Cropping sequence and year' Juveniles per 100 cm
3 
soil
1985 1986 1987 1988 1989 1990 1985 1986 1987 1988 1989 1990
P(-) P(-) P(-) P(-) P(-) P(-) 579 72 144 97 155 283
P(+) P(+) P(+) P(+) P(+) P(+) 539 15 281 84 151 226
C(-) P(-) C(-) P(-) C(-) P(-) 5 41 1 59 2 128
C(+) P(-) C(+) P(-) C(+) P(-) 10 23 5 17 6 128
C(-) P(+) C(-) P(+) C(-) P(+) 24 15 2 69 7 68
C(+) P(+) C(+) P(+) C(+) P(+) 6 10 7 47 5 59
C(-) C(-) P(-) C(-) C(-) P(-) 15 16 24 8 6 88
C(+) C(+) P(+) C(+) C(+) P(+) 14 12 65 11 4 50
FLSD (P= 0.05): 26 116 43 47 114
() = without nematicide; (+) = with at-plant application of Temik 15G at three lb. a.i. per acre row in an eight-in.-wide band.
TABLE 3. EFFECT OF VARIOUS CROPPING SYSTEMS WITH PEANUTS (P) AND COTTON (C) ON THE INCIDENCE OF WHITE MOLD (SCLEROTIUM
ROLFSI) IN PEANUTS AT THE END OF A SIX-YEAR EXPERIMENT IN A FIELD AT THE WIREGRASS SUBSTATION, HEADLAND
Loci
Cropping sequence and year' per
100 m
1985 1986 1987 1988 1989 
1990 row
2
P(-) P(-) P(-) P(-) P(-) 
P(-) 137
P(+) P(+) P(+) P(+) P(+) 
P(+) 145
C(-) P(-) C(-) P(-) C(-) 
P(-) 110
C(+) P(-) C(+) P(-) C(+) P(-) 89
C(-) P(+) C(-) P(+) C(-) P(+) 96
C(+) P(+) C(+) P(+) C(+) P(+) 100
C(-) C(-) P(-) C(-) C(-) P(-) 90
C(+) C(+) P(+) C(+) C(+) P(+) 84
FLSD (P = 0.05): 25
() = without nematicide; (+) = with at-plant application of Temik 15G at three lb. a.i. per are row in an eight-in.-wide band.
2
Number of disease loci ("hits'") of <30 cm per 100 m of row.
TABLE 4. EFFECT OF SEVERAL PRODUCTION SYSTEMS WITH COTTON (C) AND PEANUTS (P) ON THE NET ECONOMIC RETURN FROM THE
1990 PEANUT Crop Based on Current Prices for Support and World Market Price for Peanuts
Cropping sequence and year' Net return/ha in U.S.$
2
1985 1986 1987 1988 1989 1990 World price Support
P(-) P(-) P(-) P(-) P(-) P(-) 
-136.72 -90.50
P(+) P(+) P(+) P(+) P(+) P(+) 14.97 29.32
C(-) P(-) C(-) P(-) C(-) P(-) 
53.65 105.05
C(+) P(-) C(+) P(-) C(+) P(-) 
118.87 232.76
C(-) P(+) C(-) P(+) C(-) P(+) 
97.74 191.38
C(+) P(+) C(+) P(+) C(+) P(+) 105.42 
206.43
C(-) C(-) P(-) C(-) C(-) P(-) 
138.43 271.07
C(+) C(+) P(+) C(+) C(+) P(+) 
207.60 406.51
'(-) = without nematicide; (+) = with at-plant application of Temik 15G at three lb. a.i. per acre row in an eight-in.-wide band.
2
Calculations based on a production cost of U.S. $1,307 per ha without Temik 15G and U.S. $1,391 per ha with Temik 15G,
and prices of $701 per ton and $358 per ton for support and world market peanuts, respectively.
TABLE 5. EFFECT OF PENSACOLA BAHIAGRASS ON MELOIDOGYNEAREARIA J2 POPULATION DENSITY AND ON THE YIELD OF
FLORUNNER PEANUTS IN A TWO-YEAR FIELD EXPERIMENT CONDUCTED AT THE WIREGRASS SUBSTATION, HEADLAND
Cropping sequence and treatment' M. arenaria J22 Peanut yield (lb./acre)
1986 1987 1986 1987 1986 1987
Peanut (-) Peanut (-) 255 277 2,303 1,600
Peanut (+) Peanut (+) 8 283 3,553 2,333
Bahiagrass Peanut (-) 15 163 
2,034
Bahiagrass Peanut (+) 2 89 2,495
Bahiagrass Bahiagrass 5 12
LSD (P = 0.05) 94 113 727 387
(-) = without nematicide; (+) = Temik 15G applied at-plant at three lb. a.i. per acre row in an eight-in.-wide band.
2
Number per 100 cm
3
soil two weeks before harvest.
[8]
Bahiagrass in Rotations Shows Promise
for Boosting Peanut Yields
J.C. Jacobi, P.A. Backman,
R. Rodriguez-Kibana, and
D.G. Robertson
SOILBORNE diseases of peanuts are on the
increase in Alabama. Both white mold and limb
rot have become more severe problems as irrigated
acreage has increased and rotation use and length
of rotation have declined. The bottom line has
been a gradual but consistent decline in peanut
yields over the past few years.
Unfortunately, fungicidal control for soilborne
diseases is limited. Terraclor? is the only
fungicide currently recommended for control of
white mold, but it does not control limb rot. The
experimental fungicides Folicur? and Spotless?
have given excellent control of peanut leafspot,
white mold, and limb rot in field trials, but these
materials are not registered for use on peanuts.
Under existing conditions, crop rotations appear
to offer the best hope for reducing severity of
soilborne peanut diseases, and this approach is
being emphasized in Alabama Agricultural
Experiment Station (AAES) research. Suitable
rotations are being sought despite the problems of
a lack of economically attractive rotation crops,
and the broad host ranges of the white mold and
limb rot fungi.
Peanut rotations commonly used in Alabama
include either corn, cotton, sorghum, or soybeans.
Since previous AAES research has shown that
bahiagrass reduces root-knot nematode
populations, bahiagrass was included, along with
corn, in a long-term rotational study with irrigated
peanuts at the Wiregrass Substation, Headland.
Results indicate that either a one-year rotation
with corn or one- and two-year rotations with
bahiagrass did not significantly reduce white mold
severity (Table 1). Rotations of one to two years
between peanut crops are not long enough to
reduce white mold severity due to the ability of
the white mold pathogen to remain in the soil for
an extended time period (three to four years).
Three- and four-year rotations between peanut
crops are generally required to reduce white mold
severity.
Limb rot severity was reduced 16% and 43%
by one- and two-year rotations, respectively, with
bahiagrass when compared to continuous peanuts
(Table 1). A one-year rotation with corn did not
significantly reduce limb rot severity, because corn
is a host of the causal fungus of the disease. All
rotations increased yields over continuous peanuts
(Table 2). Peanut yields following a two-year
rotation with bahiagrass were 44% higher than
yields of nonrotated peanuts.
The effects of the nematicide Temik@ and the
fungicide Folicur also were evaluated for each
rotational system. Chemical treatment increased
yields and reduced soilborne disease intensity,
regardless of crop rotation. However, yield
increases with these chemicals were higher for
rotated peanuts than nonrotated peanuts. In
several cases, yields were increased by 1,000 lb.
per acre. Similar yield increases with Folicur have
been seen in tests conducted across the Southeast.
However, until Folicur is registered by the EPA,
growers must rely largely on management
practices, such as rotation, to minimize yield
losses to soilborne diseases.
These preliminary results indicate that one- or
two-year rotations with bahiagrass can
significantly increase yields over continuous
peanut production. While the reasons for yield
increases with bahiagrass rotations are not entirely
understood, reduced severity of soilborne diseases,
such as limb rot and root-knot, along with
enhanced soil physical properties are thought to be
important factors. Although white mold severity
was not significantly reduced in either bahiagrass
rotation, rotations longer than two years between
peanut crops may reduce white mold disease
severity.
Jacobi, Backman, Rodriguez-Klibana, and
Robertson, Department of Plant Pathology.
[9]
TABLE 1. EFFECTS OF CROP ROTATION AND CHEMICAL TREATMENT ON DISEASE INTENSITY OF WHITE MOLD AND RHIZOCTONIA LIMB ROT
IN IRRIGATED FLORUNNER PEANUTS
White mold Limb rot
Crop rotation' Treatment
2  
hits' lesions'
Peanuts-peanuts-peanuts ............................... ...... .. (-) 32.9 10.5
(+) 9.4 6.8
Peanuts-corn-peanuts ..................................................... (-) 37.5 10.0
(+) 7.8 
6.1
Peanuts-bahiagrass-peanuts ........................................... ( 35.9 8.8
(+) 7.8 3.8
Bahiagrass-bahiagrass-peanuts ...................................... ... (-) 32.9 6.0
(+) 4.0 3.8
'Crops grown in 1988, 1989, and 1990, respectively.
k-) = no Temik, no Folicur, (+) = Temik applied at plant at three lb. a.i. per acre in an eight-in, band and Folicur applied twice during
the season at a rate of 0.225 lb. a.i. per acre.
3
Average number per 100 ft. of row.
Total number per five lateral limbs.
TABLE 2. EFFECtS OF CROP ROTATION AND CHEMICAL TREATMENT ON YIELD OF
IRRIGATED FLORUNNER PEANUTS
Change in
Crop rotation' Treatment2 Pod yield over Additional
yield/ continuous yield with
acre peanuts
3  
Folicur-Temik
Lb. Lb. Lb.
Peanuts-peanuts-peanuts ........................ (-) 2,693 --- + 634
(+) 3,327
Peanuts-corn-peanuts ................................. (-) 2,978 + 285 +1,569
(+) 4,547
Peanuts-bahiagrass-peanuts .................... (-) 3,127 + 434 + 948
(+) 4,075
Bahiagrass-bahiagrass-peanuts ................... (-) 3,878 +1,185 +1,122
(+) 2,693
'Crops grown in 1988, 1989, and 1990, respectively.
2(.) = no Temik, no Folicur, (+) = Temik applied 
at-plant at three lb. a.i. per acre in an eight-in, 
band and Folicur applied twice
during the season at a rate of 0.225 lb. a.i. per acre.
3
Change in yield per acre from continuous peanuts due to rotation effect.
*Per acre yield increase with chemical treatment for the same crop rotation.
[10]
Potential Yield Increases from a
New Fungicide for White Mold
Control in Peanuts
A.K Hagan, J.R. Weeks, K.L Bowen,
W.A. Miller, and D.L. Hartzog
WHITE MOLD is the most damaging disease
of peanuts in Alabama. Annual losses to this
disease have been estimated at 20% of expected
yields. Greatest losses have usually occurred in
fields cropped to peanuts every other year. The
objective of this study was to determine the
potential impact of the unregistered new fungicide
Moncut@ on peanut production in Alabama.
Trials were conducted in 16 farm fields in
1991, and in 21 fields in 1992. One of the
following cropping patterns was followed in each
field: continuous peanut production (three-year
minimum), one year of peanuts behind one year of
corn/grain sorghum/clean fallow, peanuts after two
to three years of cotton/corn, and peanuts behind
bahiagrass (five-year minimum). Six nontreated
control plots were paired with treated plots.
Treatments were applied approximately 60 to 70
days after planting with Moncut 50W at two lb.
per acre as a full canopy spray at 15 gal. per acre.
The occurrence of other diseases and
nematodes was periodically monitored. Plots were
rated for white mold after inverting, then
harvested.
In 1991, an 82% reduction in the incidence of
white mold was seen in all Moncut-treated plots
across all four rotations (Table 1). The lowest
level of disease control (60%) occurred in those
fields where peanuts followed bahiagrass, while
the best protection from white mold was noted
where peanuts followed two or more years.
Despite heavy disease pressure, yield increases
after treatment with Moncut (23.3%) were largest
where peanuts were grown every other year.
Under modest disease pressure, yield increases of
14% were also obtained in fields cropped to
peanuts every third year. Smaller yield increases
were seen in fields in continuous peanut
production. In peanuts behind bahiagrass, disease
pressure was light and no yield gains were noted.
Overall, an application of Moncut increased
average peanut yields across all rotations by 18.1%
over that of the nontreated plots. Yield increases
in selected fields under severe white mold pressure
were in the range of 40 to 45% (1,700 lb. per
acre).
In 1992, Moncut provided 85% control of
white mold across all rotations (Table 2). Best
disease control occurred in those rotations with
heaviest white mold pressure. Sizable yield
increases were noted in all rotations except
bahiagrass-peanuts, where little white mold was
present. Overall, yields from the Moncut-treated
plots were 19.4% higher than yields from the
nontreated controls across all rotations.
In both years, superior control of white mold
and yield increases were obtained with a single
application of Moncut. Greatest yield increases
consistently occurred in those fields where white
mold historically has caused extensive damage.
Where disease pressure was low, such as when
peanuts were cropped after bahiagrass, Moncut had
little impact on yield.
Hagan and Bowen, Department of Plant Pathology;
Weeks, Department of Entomology; Miller, Department
of Agricultural Economics and Rural Sociology; and
Hartzog, Department of Agronomy and Soils.
TABLE 1. WHITE MOLD CONTROL AND YIELD INCREASES
IN PEANUTIS TREATED WITH MONCUT, 1991
Rotation Control Yield increase
Pct. Lb./acre Pct.
Peanuts after bahia (4) ..... 60 -181 -4.9
Peanuts every 3 yr. (4) .... 90 516 14.0
Peanuts every 2 yr. (5) .... 82 836 23.3
Continuous peanuts (3) .... 72 208 6.1
Average 82 18.1
TABLE 2. WHITE MOLD CONTROL AND YIELD INCREASES IN
PEANUTS TREATED WITH MONCUT, 1992
Rotation Control Yield increase
Pct. Lb./acre Pct.
Peanuts after bahia (5) .... 60 -63 -1.6
Peanuts every 3 yr. (9) .... 78 502 11.1
Peanuts every 2 yr. (4) .... 85 743 20.4
Continuous peanuts (2) ... 89 768 19.3
Average 85 19.4
[11]
Impact of Crop Rotation on Soilborne
Diseases and Nematodes in Peanuts
A.K. Hagan, K.L Bowen, J.R. Weeks,
and D.L Hartzog
CROP ROTATION has long been recognized
as a valuable component in peanut disease
management systems. For a variety of reasons,
crop rotation has been largely eliminated as a
control measure for soilborne diseases on Alabama
peanut farms. A study was conducted to
determine occurrence of destructive diseases, such
as southern stem rot and Rhizoctonia limb rot, in
Alabama peanut fields with a variety of cropping
histories; document disease-related losses in those
fields; and assess the role of crop rotation as a
disease management tool.
Trials were established in 16 fields in 1991,
and in 21 fields in 1992. The fields had one of
the following rotation sequences: continuous
peanut production (three-year minimum), one to
two years of peanuts behind one year of corn/grain
sorghum/clean fallow, peanuts after two to three
years of cotton/corn/or other nonhost crop of the
white mold fungus (Sclerotium rolfsii) and the
peanut root-knot nematode, and peanuts after
bahiagrass (five-year minimum). Defoliation from
early leafspot and root-knot larval populations
were periodically determined during the growing
season. Plots were rated for disease after
inverting, then harvested with a combine.
In 1991, white mold and root-knot nematodes
were largely absent and yields were highest when
peanuts were grown behind bahiagrass (Table 1).
Where peanuts followed two to three years of corn
or cotton, white mold incidence increased, but no
nematode pressure occurred. Yields were slightly
lower in these fields than in those where peanuts
followed bahiagrass. The numbers of white mold
hits peaked where peanuts were cropped every
other year. Light nematode pressure also was
noted. Yields in these fields did not differ
substantially from those fields cropped less often
to peanuts. Lowest yields, along with moderate
white mold damage, heavy leafspot defoliation,
and severe nematode pressure were seen in fields
in continuous peanut production.
In 1992, white mold incidence and root-knot
pressure again were exceptionally low where
peanuts were grown after bahiagrass (Table 2).
Early leafspot and, to a lesser extent, limb rot
greatly suppressed yields in several fields in a
bahiagrass-peanut rotation sequence. Despite
increases in numbers of white mold hits and
root-knot larvae, yields in fields in a three-year
rotation were similar to those of the
bahiagrass-peanut rotation. Serious white mold
damage was seen in only one of the nine fields
and nematode damage occurred in two of the nine
fields in the three-year rotation category. Fields
cropped every other year to peanuts had moderate
white mold damage and modest nematode
pressure, which resulted in a slight reduction in
yield as compared to other rotations. Lowest
yields were recorded in fields in continuous
production, which apparently were due to a
combination of white mold and root-knot
nematode damage. Crop rotation had little effect
on defoliation from early leafspot and on
development of limb rot.
Adoption of better crop rotations by Alabama
peanut producers should result in some yield gains
due to a reduction in damage caused by white
mold and root-knot nematode. Lowest white mold
and nematode pressure was consistently seen in
the bahiagrass-peanut cropping sequence. Peanuts
cropped every three years generally yielded well
and suffered only moderate white mold damage.
Unfortunately, most of Alabama's peanut land is
cropped to peanuts every other year. Producers
following this cropping sequence risk sizable yield
losses due to white mold and possibly also to
root-knot nematode, along with the added
production costs needed for their control.
Nematodes displaced white mold as the most
destructive pest on continuous peanuts and the
combination of the two in these fields further
reduced yields. Disease and nematode pressure
was not consistent from field to field in any
rotation category except the bahiagrass-peanut
rotation where white mold and nematodes were
largely absent. No matter how favorable the
rotation for diseases or nematodes, some fields in
each of the other rotation categories escaped
significant damage.
The development of Rhizoctonia limb rot
apparently was not influenced by cropping
sequence.
Hagan and Bowen, Department of Plant Pathology;
Weeks, Department of Entomology; and Hartzog,
Department of Agronomy and Soils.
[12]
TABLE 1. YIELDS AND INCIDENCE OF WHITE MOLD, IzAFSPoT DEFOLIATION, AND ROOT-
KNOT LARVAE IN FOUR ROTATION CATEGORIES, 1991
Rotation White mold Leafspot Root-knot Yield
hits/100 ft. defoliation nematodes lb./acre
No. Pct. No?
Peanuts after bahia (4)' .............. 03 33.3 5.5 3,859
Peanuts every 3 yr. (4) ............... 5.6 30.0 .0 3,692
Peanuts every 2 yr. (5) ............... 13.0 35.0 10.0 3,608
Continuous peanuts (3) ............... 5.8 41.5 1,520.7 3,222
'Numbers of fields in each rotation category are in parenthesis.
'Number of larvae per 100 cc soil sample.
TABLE 2. YIELDS AND INCIDENCE OF WHITE MOLD, LEAFSPOT DEFOUATION, AND ROOT-KNOT LARVAE IN FOUR ROTATION
CATEGORIES, 1992'
Rotation White mold Leafspot Root-knot Limb Yield,
hits/100 ft. defoliation nematodes rot lb./acre
No. Pct. No.5 Pct.
Peanuts after bahia (5)2 .......................... 0.1 35.6 0.0 5.5 3,932
Peanuts every 3 yr. (9) .......................... 5.0 32.8 75.6 5.6 4,035
Peanuts every 2 yr. (4) .......................... 14.7 31.8 48.5 .0 3,645
Continuous peanuts (2) ......................... 11.3 27.4 124.0 .0 3,229
'Preliminary information compiled from raw data.
2
Numbers of fields in each rotation category are in parenthesis.
'Numbers of larvae per 100 cc soil sample.
Peanut Economics
W.A. Miller
ECONOMIC research on peanuts at the
Wiregrass Substation, Headland, focused on
comparisons of recommended (conventional) and
reduced cost management practices during the
1982-85 period. Treatments involving row
spacing, seeding rate, weed control, leafspot
control, and drying practices were evaluated.
Among the nonconventional treatments, only the
use of twin row spacing produced higher yields
and net returns with any consistency.
During the 1986-88 period the economic
research on recommended versus reduced cost
practices continued, but the treatments were
changed. Reduced cost treatments involving
tillage, seeding rate, weed control, and disease
control were evaluated. The use of a 60-lb.
seeding rate produced about the same yields as a
100-lb. seeding rate and increased net returns.
A long-term, sod-based, peanut rotation study
was started in 1988 at the Wiregrass Substation.
A multidisciplinary group of researchers is
working with this experiment, which is expected
to continue through 1995. In addition to including
all possible combinations of one through four
years of bahiagrass followed by one through four
years of peanuts, the test includes a continuous
peanut treatment and an every other year rotation
of peanuts after corn. The table summarizes the
average yields, graded values of peanuts, and net
returns attributable to the these two cropping
systems.
Peanut yields, graded values, and net returns to
land and management appeared to respond
favorably to the rotation treatment. The response
to irrigation was not consistent. Neither the
[13]
continuous peanut or corn-peanut cropping systems
generated a net return under irrigation (on the
average) over the study period. Analysis of the
net return data suggested that irrigation can do
more harm than good when pests and diseases are
not adequately controlled in these cropping
systems. The next step in this research project
will be to evaluate the economic performance of
alternative bahiagrass/cattle-peanut rotations.
Miller, Department of Agricultural Economics and
Rural Sociology.
AVERAGE YIELDS, GRADED VALUES, AND NEr RETURNS OF CONTINUOUSLY CROPPED PEANUTS AND PEANUTS ROTATED WITH
CORN, 1989-92'
Yields Nonirrigated Irrigated
Continuous peanuts, lb./acre ........................................ ......................... 2,362 2,203
Rotated peanuts, lb.Iacre ........................................ ........................ 2,503 2,633
Corn, bu./acre ................... ........ ...................................... 72 132
Graded values, dol./ton
Continuous peanuts ........................................................................................ . 663.43 660.12
Rotated peanuts...................................................... 668.53 662.91
Annual net returns by crops, dol.facre
Continuous peanuts ..................................................... 80.28 -84.88
Rotated peanuts...................................................... 117.93 16.72
Corn .......................................................................................... -12.46 -21.51
Annual net returns by cropping system, dol./acre
Continuous peanuts............................................................................ 80.28 -84.88
Corn-peanut rotation........................................................................... 52.74 - 2.40
'Net returns are the residual returns to land and management. The rotation treatment was an every -other-yea r rotation of
peanuts following corn. Corn yields and net returns were averaged over the 1988-91 period. Peanut yields, graded values, and
net returns were averaged over the 1989.92 period. The following information was used to compute net returns: (1) a 4:1 ratio
of quota peanuts to additional peanuts, (2) a market price of $300 per ton for additional peanuts, and (3) a market price of
$2.735 per bushel for corn. Peanut production costs averaged $302 (variable) and $164 (fixed) per acre for the nonirrigated test
and $345 (variable) and $245 (fixed) for the irrigated test during the period 1989-92. In addition, peanut quota cost about $.08
per lb. These costs did not include certain costs normally incurred by peanut growers, such as crop insurance premiums,
marketing assessments, and the cost of a winter cover crop. Both the Florunner peanuts and corn were produced using
conventional production practices. Irrigation of both corn and peanuts was scheduled based on the water needs of the
peanuts.
[14]
FERTILITY
Tillage, Subsoiling, Starter Fertilizer
Combinations, and Starter Fertilizer
Placement Comparisons for Peanuts
J.T. Touchton
STUDIES were conducted on a Dothan sandy
loam soil at the Wiregrass Substation, Headland,
to evaluate the effects of tillage, subsoiling, starter
fertilizer, and starter fertilizer placement on peanut
yields. Peanuts were grown in a three-year
rotation that consisted of cotton-corn-peanuts.
After harvesting each fall the field was disked
lightly and seeded in rye. Tillage treatments were
no tillage into killed rye and disk-chisel-disk.
Subsoiling treatments were no subsoiling and
in-row subsoiling 12 to 14 in. deep at planting.
Starter fertilizer combinations consisted of none;
nitrogen (N); nitrogen and phosphorous (N-P); and
nitrogen, phosphorous, and potassium (N-P-K).
Fertilizer placement was 3 X 2 with and without
subsoiling and 6 to 10 in. below the seed with
subsoiling. The 3 X 2 fertilizer placement was
approximately three in. from the row and two in.
deep. Rates of N, P, and K were approximately
23, 10, and 6 lb. per acre, respectively. The
residual sol P and K levels were high and
remained high throughout the duration of the
study.
With all possible combinations of treatments
there were 22 treatments with three years of data
for a total of 66 comparison points when yields
were averaged over replications. Some of the
results were easy to interpret, but others were not.
Within the conventional tillage system, in-row
subsoiling with or without starter fertilizers either
had no effect on yields or slightly reduced yields.
Since in-row subsoiling within the conventional
tillage system could not be considered profitable
with or without the starter fertilizer, the only
feasible placement method for the starter fertilizer
would be the 3 X 2 application. In 1983, which
was not a very good climatic year for peanut
production, N alone and the N-P combination had
essentially no effect on yields (Table 1), but K in
the starter reduced yields. In 1984, starter
fertilizer improved yields, but N alone was
adequate. In 1985, best yields were obtained with
the N-P-K combination. The three-year average
yields, however, suggest that a starter fertilizer
consisting of N alone would be adequate for
peanuts grown in a conventional tillage system.
When starter fertilizers were not applied in the
no-tillage system, yields averaged 3,100 and 2,600
lb. per acre per year with and without in-row
subsoiling, respectively. Although the starter
fertilizers improved yields when the subsoiler was
not used, the yields were still inferior to those
obtained with subsoiling.
With in-row subsoiling in the no-tillage system,
the optimum starter fertilizer combination and
placement method varied among years (Table 2).
Based on the three-year average yield, the
optimum combination was the N-P-K, and deep
placement was as effective as the 3 X 2
placement.
The difference in yields between tillage systems
also varied among years, and the difference was
dependent on the starter fertilizer combination and
placement method. When averaged across all
treatments and years, yields with conventional
tillage were 180 lb. per acre per year higher than
with no tillage. The need for starter fertilizers was
more critical with no tillage than conventional
tillage. The average yield response to the best
starter fertilizer combination was 240 lb. per acre
per year with conventional tillage and 420 lb. per
acre per year with no tillage. Studies with other
crops have also shown that the most critical need
for starter fertilizers occurs in no-tillage systems.
The data also suggest that if the correct cultural
practices are used, yields obtained with no tillage
can be as high as yields obtained with
conventional tillage.
Touchton, Department of Agronomy and Soils.
[15]
TABLE 1. YIED OF PEANUTS GROWN IN A CONVENTIONAL TILLAGE SYSTEM AS
INFLUENCED BY 3x2-PLACED COMBINATIONS OF STAPrER FERTIUZER
Starter Year 3-yr.
fertilizer average
1983 1984 1985
Peanut yield, lb./acre
None ......................... 2,820 2,950, 4,390 3,390
N ........................ 2,940 3,860 4,100 3,630
N-P .......................... 2710 3,780 4,380 3,620
N-P-K........................ 2,290 3,720 4,650 3,550
TABLE 2. YIELD OF PEANUTiS GROWN IN A NO-TILAGE SYSTM WITH IN-Row SUBSOING
AS INFLUENCED BY PLACEMENT OF STARTER FERTILZER COMBINATIONS
Starter Fertilizer 3-yr.
fertilizer placement 1983 1984 1985 average
Peanut yield, lb./acre
None --- 1,830 3,180 4,300 3,100
N deep 2,420 3,290 4,480 3,400
3 X 2 1,820 3,630 4,680 3,380
N-P deep 2,240 3,160 4,510 3,300
3 X 2 1,720 3,760 4,630 3,370
N-P-K deep 2,220 3,460 4,840 3,510
3 X 2 2,160 3,600 4,860 3,540
Calcium Requirements for
Maximum Yield
J.F. Adams and D.L Hartzog
THlE ALABAMA Agricultural Experiment
Station initiated fertility experiments with peanuts
in the early 1900's. Through the years production
practices and peanut cultivars have changed
dramatically. Auburn University has and will
continue to do fertility research on peanuts to meet
current and future changes. From 1967 to 1993
more than 350 on-farm soil fertility experiments
have been conducted. The following summary
covers only those experiments dealing with
calcium.
Calcium is the most limiting plant nutrient for
peanut production. The addition of calcium
prevents "1pops" and increases yield and grade.
The primary source of calcium in the past has
been gypsum or landplaster, but the primary
calcium source has changed to agricultural
limestone. This change was based on research that
has established a minimum soil-test calcium
concentration for the Florunner cultivar. The 300-
lb.-per-acre requirement for Florunner was
developed from more than 75 on-farm experiments
(see figure). On-farm experiments are continuing
to define this critical soil calcium concentration for
GK 7, Sunrunner, and Southern Runner cultivars.
The data indicate that there will be little difference
in calcium requirement for maximum yield and
grade for these new cultivars.
Many calcium source comparison experiments
have been conducted on-farm from 1967 to present
using gypsum, gypsum rates, calcitic and dolomitic
[16]
lime, lime suspensions, 420 landplaster, and basic
slag. Seven on-farm experiments were conducted
to determine if less gypsum could be used. The
experiments showed that 250 lb. per acre of
gypsum provided yields as high as the traditional
500-lb.-per-acre rate, even on soils that had as low
as 120 lb. per acre of soil-test calcium. When
comparing the 500-lb.-per-acre rate of gypsum
with calcitic lime in 12 on-farm experiments, lime
was superior to gypsum in two of five experiments
that had increased yield due to added calcium and
in no case did additional gypsum on lime
treatments increase yield. Lime proves to be as
good a calcium source as gypsum and there is no
benefit to adding gypsum to freshly limed soil.
Lime sources also were compared to determine
if dolomitic limestone supplied adequate calcium.
Six on-farm experiments showed that dolomite
was equal to calcitic lime, except for one
experiment where the dolomitic lime gave a higher
yield. This increase was assumed to be a response
to the added magnesium and not calcium since the
soil-test level was only seven lb. per acre. Lime
was also compared to basic slag as a calcium
source. When basic slag was incorporated into the
top three to four in. of the soil, both were equally
effective in increasing yield. But when basic slag
was applied in the same manner as gypsum, then
basic slag had very little value.
Lime suspensions were compared in seven on-
farm experiments to dry agricultural limestone at
a 500-lb.-per-acre rate and the recommended rate.
The lime slurry was as effective as dry lime when
applied at the recommended rate, but neither lime
source gave maximum yields at the 500-lb.-per-
acre rate.
Adams and Hartzog, Department of Agronomy and
Soils.
Relative yield, %
120
100-_
0 100 200 300 
400 500 600
Soil. calcium, lb./acre
Experiments show that 300 lb. Ca per acre
is required for Florunner peanuts.
[17]
Have We Been Overfertilizing
Our Peanuts?
C.C. Mitchell and J.F. Adams
PERCEIVED differences in fertilizer
recommendations across the peanut growing
regions of the Coastal Plain prompted peanut
researchers in Alabama, Georgia, Florida, and
other peanut growing states to take a new look at
the research that provides the basis for current
fertilizer recommendations. After four years of
scrutiny, the general conclusion about phosphorous
(P) and potassium (K) recommendations is that
they are too high. By adjusting soil test
interpretations and recommendations for peanuts
and encouraging proper fertilization of the rotation
crop, yields will improve with less direct inputs.
The critical soil test value is that level of
extractable nutrient that separates the "medium"
from the "high" rating. No yield response to
additional application of a particular nutrient is
expected above the critical value.
For Alabama, a critical soil test value of 50 lb.
P per acre and 80 lb. K per acre are currently
used. However, research suggests that these
values should be reduced.
After more than 60 years of fertility
experiments on a Dothan sandy loam soil in
Alabama, no peanut yield response has ever been
shown from P fertilization. A research-based
interpretation of current research information
regarding soil test P calibrations for peanuts would
suggest dramatic changes in current critical values
for runner-type peanut production. This would
result in little or no P fertilizers recommended on
most Coastal Plain soils. A more realistic critical
soil test value of 20 lb. per acre has been
proposed.
In general, there are contradictions and poor
correlations between soil test K and response to K
fertilizers by peanuts. Research has shown
positive, negative, and no response to K. Recent
on-farm tests in Alabama suggest that the critical
soil test value for K should be about 26 lb. per
acre. Evidence indicates a need to consider depth
to the subsoil and subsoil K levels when
interpreting soil test levels. However, 40 lb.
extractable K per acre has been proposed as a
more acceptable critical value for runner-type
peanuts on all Coastal Plain soils.
These results suggest that modifying soil test
calibration, interpretation, and recommendations
for P and K on peanuts in Coastal Plain soils will
require dramatic changes in existing soil test
calibrations. Programs should emphasize soil
testing and proper fertilization for crops in rotation
with peanuts rather than direct fertilization of
peanuts. The resulting lower direct inputs, in
combination with the yield-enhancing benefits of
crop rotation, could help assure the profitability of
peanut production in Alabama.
Mitchell and Adams, Department of Agronomy
and Soils.
[18]
PLANTING DATES,
AND SEED
Early Planting and Reduced Tillage
Help Control Lesser Cornstalk
Borer In Peanuts
T.P. Mack, H.W. Ivey,
and LW. Wells
THE HOT, dry growing season of 1990 was
ideal for the lesser cornstalk borer (LCB).
Population outbreaks of this insect pest of peanuts,
sorghum, small grains, and soybeans are associated
with hot and dry conditions. Although nothing
can be done about the weather, results of Alabama
Agricultural Experiment Station research suggest
that early planting and reduced tillage can help
reduce the problem.
Since population outbreaks usually develop in
hot, dry weather, the potential exists for the
reduction of lesser cornstalk borer damage to
peanuts by altering planting dates so plants are
less exposed to this type of weather. For example,
by the time summer droughts occur, early planted
peanuts would likely produce larger plants, making
them less attractive to LCB than later planted
peanuts. Tillage may also affect LCB population
density by altering soil moisture and daily
maximum soil temperatures.
A field study was begun at the Wiregrass
Substation, Headland, in 1986 to determine if
planting date and tillage practices affected LCB
abundance. Florunner peanut seed were planted in
36-in. rows in a Dothan sandy loam soil.
Herbicides were applied according to Cooperative
Extension Service recommendations, and no
insecticides were used. Each treatment plot was
eight rows wide by 50 ft. long. Two planting
dates were used (May 23 and June 11), along with
three tillage systems (conventional, reduced tillage,
and burned stubble).
The conventional tillage treatment was defined
as turning and disking before planting. Reduced
tillage involved planting peanuts inito wheat
stubble with a Ro-til? subsoiler and planter
combination. The burned stubble treatment was
similar to the reduced tillage except that the
SEEDING RATES,
QUALITY
stubble was burned off before planting. This
treatment was included because smoke attracts
adult LCB moths.
The abundance of LCB larvae, which is the
damaging stage, was monitored with pitfall traps.
Two traps per plot were randomly placed in a
selected central row within each plot. Traps were
monitored weekly for most of the growing
season.
Fewer larvae were caught in pitfall traps in the
early planted, reduced tillage plots than in the
conventional or burned stubble plots. This was
especially evident for samples collected on July 15
and July 22, when 3.4 and 7.0 times more larvae,
respectively, were caught in traps in
conventionally tilled plots than in the reduced
tillage plots. Daily maximum soil temperatures
are usually lower in plots containing thick stubble,
apparently because the stubble shades the soil.
Since LCB larvae are subterranean and cold-
blooded, their growth rate would be slowed by
such temperature reduction.
The number of larvae caught per trap showed
no difference among late planted tillage systems.
This suggests that all plants were susceptible to
LCB attack at this time. Larval populations were
larger in late than in early planted peanuts, with a
peak of 5.7 larvae per trap on July 25 in
conventionally tilled plots.
The early planting date yielded more peanuts
than the late planting date, regardless of tillage
system, 2,193 and 1,694 lb. per acre, respectively.
It is well known that the LCB is a hot and dry
weather pest. In 1986, most of the hot weather
occurred in July; 26 days had a daily maximum
temperature of 95?F at Headland. The late planted
peanut plants were smaller than the early planted
peanuts because late planting was done during the
drought. Thus, it should not be surprising that the
late planted peanuts yielded significantly less than
those that were planted early.
The month of May in Alabama typically has
fewer hot days than June or July, so planting
peanuts earlier to help avoid weather conducive to
[19]
LCB population outbreaks is probably a wise
strategy. Reduced tillage at this time may also
Number/trap/week
5
Reduced tillage
4 Burned stubble
\ Conventional tillage
3
2
1
0
help reduce the abundance of this pest on peanuts,
as indicated by the 1986 data.
Mack, Department of Entomology; Ivey and Wells,
Wiregrass Substation.
18 25 2 8 15 22 5
June July August
Sample date
Abundance of lesser cornstalk borer larvae in early planted peanuts.
Peanut Performance and Disease
Occurrence as Influenced
by Planter and Seeding Rate
G.R. Wehtje, J.R. Weeks, M.S. West
LW. Wells and P.F. Pace
IN RECENT years, "air" or "vacuum" planters
have become available to peanut growers. These
planters are advertised as being efficient in
achieving an even spacing between seeds, and this
added acurracy allows for a reduction in seeding
rate compared to rates used with conventional
planters, which would result in a cost savings.
An experiment was conducted in 1991 and
1992 at the Wiregrass Substation, Headland, to
evaluate vacuum versus conventional planters.
Peanuts were planted at 110, 90, 70, 50, and 30 lb.
per acre with both type planters. The normal
seeding rate is 90 to 100 lb. per acre. A common
lot of peanut seed was used that averaged 750
seed per lb. Both planters were operated at four
miles per hour.
[20]
Seed germination was about 70% in 1991, and
91% in 1992. Immediately after germination each
year, the spacing between each of 20 consecutive
seedlings was measured in a row that was deemed
representative of the plot. These measurements
were used to determine planter performance.
Occurence of white mold and tomato spotted wilt
virus (TSWV) was determined prior to harvest
because the severity of these diseases has been
linked to plant populations.
For all years and both planters, variation in
seedling spacing increased as seeding rate
decreased (see table). The study indicated that the
normal seeding rates (less than or equal to 90 lb.
per acre) allow seeds that are placed sufficiently
close together to work cooperatively in opening
(termed "cracking") the soil, allowing emergence.
Thus, as the spacing between adjacent drops
increased, this mutually-beneficial behavior was
limited and consequently fewer seed emerged.
Both planters were successful in achieving a
sufficient spacing between seedlings, but the
conventional planter tended to have closer spacing,
while the vacuum planter had wider spacing.
Results also revealed that the incidence of white
mold was influenced only by the seedling rate.
The additional plant material and moisture-
retaining canopy resulting from a higher seeding
rate served to enhance the number of white mold
infections. This phenomena was not influenced by
type of planter. Similar results were obtained with
(TSWV).
Across the entire experiment, yield was
influenced by the seeding rate, but not by planter.
Yields reached a maximum of 4,893 lb. per acre at
a seeding rate of 90 lb. per acre. Yield with the
110-lb.-per-acre rate was slightly less (4,794 lb.
per acre). Within each of the seeding rates, no
yield benefit could be detected that indicated one
planter offered an advantage over the other.
A vacuum planter does possess a more
technologically advanced seed metering system.
However, in peanuts under field operation,
confounding factors such as seed viability and
emergence renders any additional precision relative
to that offered by the conventional planter nearly
insignificant. These data serve to emphasize the
importance of seeding rate in achieving maximum
yield. Planter selection can not be seen as a
means of reducing seeding rate.
Wehtje Department of Agronomy and Soils; Weeks,
Department of Entomology; West, Department of
Research Data Analysis; Wells and Pace, Wiregrass
Substation.
[21]
UNIFORMITY OF PLANT SPACING, OCCURRENCE OF DISEASE AND YIELD OF PEANUTS AS INFLUENCED BY SEEDING RATE AND PLANTER TYPE
Vacuum planter Conventional planter
Seeding
rate Plant spacing White TSWV Yield Plant White TSWV Yield
variability mold spacing mold
variability
Lb./acre Sd Loci/ Loci/ Lb./acre Sd Loci/ Loci/ Lb./acre
plot plot plot plot
1991
30 ............................ 8.21 3.3A
2
- 6.6A 4,154B 10.9 2.6B 5.4A 4,149B
50 ............................ 6.3 3.3A 3.8B 4,623A 6.6 3.8AB 3.7B 4,647A
70 ............................ 4.1 3.6A 2.6B 4,823A 3.8 3.9AB 3.9B 4,743A
90 ............................ 3.4 3.8A 3.3B 5,004A 3.9 3.5AB 1.5C 4,901A
110 .......................... 3.0 4.5A 2.5B 4,890A 3.4 4.1A 2.6BC 5,031A
Average .................. 5.0 3.7 3.8 4,700 5.7 3.6 3.3 4,694
1992 7.3A
30 ............................ 5.1 7.OA 5.6A 4,558A 6.5 8.3A 6.5A 4,340B
50 ............................ 3.5 8.9A 6.3A 4,632A 4.1 8.5A 4.3B 4,626AB
70 ............................ 2.5 8.3A 4.1B 4,832A 2.8 8.1A 3.3B 4,61 lAB
90 ............................ 2.1 8.8A 3.6B 4,881A 2.6 9.1A 3.8B 4,787A
110 ........................... 1.9 9.2A 3.1B 4,647A 2.0 8.3 3.9B 4,606AB
Average .................... 3.0 8.4 4.6 4,710 3.6 4.3 4,593
1991-92, pooled 4.6A
30 ............................ 6.6 5.4A 6.1A 4,356C 8.3 6.OA 4,245B
'Indicates that standard deviation values between the two planters, within a common seeding rate, are significantly different according to an F test at the 5%
level of probability.
2
Means within a column followed by the same letter 
are equivalent according to Duncan's multiple range 
test at the 5% level of probability.
'Indicates that comparable mean values between the vacuum and conventional planter were different according to an LSD comparison at the 5% level.
Extra Calcium is Needed for Peanut Seed
D.L. Hartzog and J.F. Adams
PEANUT yields and grades are highly affected
by the level of calcium in the soil. A calcium
deficiency causes lower yields, reduces the
percentage of sound mature kernels (SMK), and
also decreases seed quality by inhibiting
development of the plumule, which is essential for
germination.
On-farm experiments in Alabama during the
past two decades have defined the soil calcium
concentration required for maximum yield and
grade of Florunner peanuts. However, little work
has been done to determine the calcium
requirements for producing high quality seed. An
Alabama Agricultural Experiment Station study
was initiated to identify the soil calcium
concentrations required for maximum yields and to
demonstrate the role of supplemental gypsum in
the production of high quality Florunner peanut
seed.
Experiments were conducted at 13 sites from
1987 to 1989. Treatments included gypsum,
topdressed over the row at the early bloom stage
at 500 lb. per acre, and no gypsum. Farmers
followed normal production practices, except for
the use of gypsum and harvesting.
Yields were significantly increased when
gypsum was added at the sites where soil calcium
concentrations were less than 300 lb. per acre (see
table). Yield did not increase for any experiment
when soil test calcium concentrations of the check
plots were more than 300 lb. per acre. An
increase in grade was seen at most sites that
experienced yield increases from the added
gypsum.
Gypsum topdressing at early bloom generally
increased seed calcium concentrations, even on
soils testing high in calcium. Seed calcium
concentrations ranged from 210 to 500 parts per
million (ppm) for check plots and 198 to 622 ppm
for gypsum-treated plots. Only two sites did not
show increased seed calcium concentration when
gypsum was applied.
Results of a standard germination test showed
that seed germination ranged between 55% and
99%. Supplemental gypsum either had a positive
effect or no effect on germination. Germination
increased due to gypsum at each site that had an
increase in yield from gypsum. Higher
germination rates also were observed at five
additional sites where no yield increases were
seen. Maximum germination was achieved at a
seed calcium concentration of 414 ppm, as shown
in the figure.
These experiments suggest that more soil
calcium is needed to produce high quality seed
than is needed to achieve maximum yield.
Hartzog and Adams, Department of Agronomy and
Soils.
EFFECr OF TOPDRESSING WITH GYPSUM ON YIELD, SMK, SEED CA CONCENTRATION, AND
GERMINATION OF FLORUNNER AT 13 SrTES FROM 1987 TO 1989
Yield SMK Seed Ca Germination
Site Soil
No. Ca No Gyp No Gyp No gyp Gyp No Gyp
gyp gyp gyp
Lb./acre Lb./acre Lb.acre Pct. Pct. ppm ppm Pct. Pct.
1 ............. 96 589 2,705* 64 76* 231 198 55 71*
2 .............. 120 2,607 3,420* 78 78 248 320* 57 76*
3............ 150 2,643 3,571* 67 73* 250 330* 73 91*
4 ................ 184 3,107 3,580* 59 59 270 360* 92 98*
5 ............... 226 2,188 3,125* 64 68* 210 300* 55 85*
6 ............. 316 5,616 5,438 78 77 310 365 85 92
7 ............... 402 1,821 2,018 59 61 360 470* 92 99*
8 ............. 418 3,446 3,375 69 69 500 520 89 97*
9 .............. 428 3,286 3,071 67 68 290 350* 93 94
10 .............. 436 3,464 3,357 78 78 473 622* 90 92
11 ........... 446 2,643 2,661 68 68 410 560* 96 99*
12 .............. 474 3,180 3,420 74 75 300 440* 89 99*
13 .............. 484 4,152 4,366 78 78 296 366* 88 94*
*Treatments are significantly different.
[23]
Germination, %
120 .
0
00
t) I
0
0I
1
Y = -43.6 + 0.66X
- 8.06x10 -
4
X2
Plateau = 95
R
2
= 0.68
20 
I
100 200 300 400 500 
600 700
Seed Calcium, mg/kg
Germination response to seed calcium.
[24]
100 I-
80
0
60
40 -
DISEASES
Application of Fungicides to Peanuts
Through Irrigation Systems
P.A. Backman, M.A. Crawford,
and E.W. Rochester
RECENT droughts have convinced many
farmers to purchase irrigation equipment for their
peanut fields. Planning for this expenditure should
encompass not only available water supply,
pumping capacity, and probable yield increases,
but should also include peripheral advantages that
can be gained by having an irrigation system.
One of the less obvious advantages of irrigation
equipment is the ability to utilize the irrigation
system to deliver pesticides along with the
irrigation water. Best suited for applying
pesticides are systems with uniform application,
such as pivots, side-roll, lateral-move, and some
solid-set systems. Traveler systems are not as
suited for applying pesticide because of
irregularities in their watering patterns.
For applying fungicides and other pesticides,
the irrigation system should be equipped with a
pesticide pump capable of accurately delivering
the product and a foot valve to prevent back-flow
of these materials into the water source.
Since 1976, experiments have been conducted
at the Alabama Agricultural Experiment Station's
Wiregrass Substation, Headland, to determine if
fungicides could be injected into irrigation lines to
control peanut leafspot and/or white mold (stem
rot). Data from the last three years are presented
in this report.
The fungi causing peanut leafspot are difficult
to control and only a few fungicides are
recommended. Late leafspot is the most difficult
to control, primarily because it produces spores in
large numbers on the lower leaf surface. It is
difficult to apply fungicides to this area even with
a well set-up ground sprayer. In Table 1, results
illustrate leafspot control tests, with comparisons
between Bravo 5OG? applied with a ground
sprayer and Bravo 500 applied through-the-line
(TTL), both at 2 1/8 pt. per acre. The 1978 test
utilized a stationary gun system; the 1979 and
1980 tests were conducted using a pivot irrigation
system. For comparison, plots receiving
fungicides applied with a ground sprayer were
always located in an area under the same irrigation
system.
Results indicate that leafspot was usually
slightly more severe in plots receiving Bravo
through the irrigation system; however, yields for
TTL Bravo plots were increased. Published
information indicates that less than 10% of the
Bravo applied TL is retained on the foliage, the
rest is washed to the soil. 'EL application of
leafspot fungicides does a better job of treating the
lower leaf surface because of the huge volume of
water applied, resulting in a total wetting of the
leaf. This may partially compensate for the low
amount of fungicide retained by the leaf.
Increased yields from TTL-applied Bravo may
result from less equipment damage (eight fewer
tractor trips), or from Bravo affecting pod and root
diseases.
A similar system was used to apply fungicides
for control of white mold, except that only two
applications were made. The first application (2
1/2 gal. Terraclor 2EC? or 2 1/2 pt. Vitavax 3F?)
was made in mid-July, and the second was made
at the same rate three weeks later. All plots were
also treated with Bravo to control leafspot; in the
1978 and 1979 tests, Bravo was applied TTL.
Evaluation of treated plots indicated good control
of white mold in all years, with yield increases in
two of three years (Table 2).
These data indicate that applying fungicides
through the irrigation system is effective in
controlling peanut diseases. Further, this method
is more economical since it does not require
tractors, spray rigs, or operators. State labels
[Alabama 24(c)] have been granted for the
application of Bravo TTL for peanut leafspot
control and for Terraclor TTL for white mold
control. Delivery of some herbicides and Sevin?
by this method also is effective.
Backmnan and Crawford, Department of Plant
Pathology; Rochester, Department of Agricultural
Engineering.
[25]
TABLE 1. COMPARISON OF EFFECTS OF FUNGICIDES APPLIED THROUGH THE IRRIGATION SYSTEM (TTL) AND BY GROUND SPRAYER ON
PEANUT LEAFSPOT AND YIELD
Bravo Yield (lb. per acre) Infected leaves Leaves lost
applications
1978 1979 1980 1978 1979 1980 1978 1979 1980
Pct. Pct. Pct. Pct. Pct. Pct.
None ........................................ 3,194 2,392 2,805 57 62 68 20 37 40
Bravo TL' ............................ 4,041 4,075 4,268 40 41 38 18 24 30
Bravo ground............................ 3,823 3,853 3,188 21 15 61 12 9 36
'TTL = through-the-line application technique.
TABLE 2. EFFECTS OF FUNGICIDES APPLIED THROUGH THE IRRIGATION SYSTEM ON INCIDENCE OF WHITE MOLD AND YIELDS
Yields (lb. per acre) White mold hits per 100 ft. row
Bravo applications
1978 1979 1980 1978 1979 1980
None .................................................................. 4,219 4,075 4,268 10.5 14.0 9.9
Bravo TTL.............................................................. 4,503 4,897 4,290 5.0 2.7 8.2
Bravo ground ..................................................... --- 4,679 4,189 --- 1.7 5.6
Disease Reduced by Management of
Southern Runner Peanuts
J.C. Jacobi, P.A. Backman,
and LW. Wells
FUNGICIDES provide good control of
leafspot on peanuts and some control of other
peanut diseases. The downside is that leafspot
control alone may cost $50-$60 per acre. Tests by
the Alabama Agricultural Experiment Station
(AAES) indicate that alternative management
practices and a new peanut variety, Southern
Runner, may cut production costs in fields with
historically high levels of peanut diseases.
Florunner is by far the most popular peanut
variety grown in the Southeast, because of its high
yield potential and other beneficial qualities.
However, it is highly susceptible to leafspot, white
mold, and limb rot. Since the release of Southern
Runner by the University of Florida, AAES
research has been developing a reduced input
fungicide program to take advantage of the new
variety's reported resistance.
Tests at the Wiregrass Substation, Headland,
compared reduced rates of Bravo@, longer
intervals between Bravo applications, and the use
of less expensive and less effective fungicides on
both Southern Runner and Florunner peanuts.
Yields of Florunner peanuts decreased more
sharply than Southern Runner when the rate of
Bravo was decreased from 1.1 lb. (1 1/2 pt.) to
0.55 lb. (3/4 pt.) and when harvest was delayed
14 days beyond optimum harvest date (Table 1).
The table also shows that the amount of
defoliation was similar in the two varieties;
however, Southern Runner apparently tolerated
leaf loss better, based on comparative yield loss.
Southern Runner has a more compact growth
habit than Florunner and produces more secondary
branches. Neither cultivar received any fungicide,
yet Southern Runner, due to increased branching,
had a relatively healthy looking canopy compared
to Florunner, which was nearly defoliated.
Delaying harvest produced greater yield loss in
Florunner than in Southern Runner, especially at
high levels of defoliation. The ability of Southern
[26]
Runner to maintain yield could become important
when adverse weather delays harvest.
Over the past three years, Southern Runner has
averaged 65% less white mold damage than
Florunner in tests at Headland (Table 2).
Observations of the two varieties indicate Southern
Runner is less susceptible to tomato spotted wilt
virus, but no differences were detected in limb and
pod rot.
These tests indicate Southern Runner can be
managed for peanut leafspot less intensively
without significant yield loss, and it is less
susceptible to white mold. It can be a good choice
in fields where serious leafspot or white mold
damage is expected. However, Southern Runner
is a later maturing variety, requiring about 10 days
longer than Florunner to reach harvest maturity.
Jacobi and Backran, Department of Plant
Pathology; Wells, Wiregrass Substation.
TABLE 1. EFFETS OF FULL SEASON SPRAY PROGRAM ON YIELD AND LEAFSPOT SEVERITY OF SOiERN RUNNER AND
FLORUNNER PEANuTS, THREE-YEAR AVERAGE
Yield/acre at:
Treatment' Optimum harvest date Harvest delayed Leafspot
14 days defoliation'
Lb. Lb. Pct.
Florunner
Bravo, 0.55 lb.......................................... 2,757 2,666 44.7
Bravo, 1.1 lb ........................................... 2,868 2,672 36.0
Manzate, 1.5 lb ........................................ 2,649 2,114 53.0
Southern Runner
Bravo, 0.55 lb.......................................... 3,124 3,344 46.1
Bravo, 1.1 lb............. ............ 3,179 3,106 31.8
Manzate, 1.5 lb ........................................ 3,143 2,837 51.2
'All rates are in pounds active ingredient per acre.
'Defoliation rated prior to harvest.
TABLE 2. INCIDENCE OF WHITE MOLD AND LIMB ROT IN PLANTING OF FLORUNNER PEANUTS, THREE-YEAR
AVERAGE
Treatment' White mold hits/8O row-ft.
Florunner
Bravo, 0.55 lb. ............................ .......................................... 8.1
Bravo, 1.1 lb ............................................................. 11.1
Manzate, 1.5 lb. ............................. ........................................... 9.9
Southern Runner
Bravo, 0.55 lb. ............................. .............................................. 3.1
Bravo, 1.1 lb . .......................... ........................................... 3.3
Manzate, 1.5 lb. ................................. .......................................... 3.7
'All rates are in pounds active ingredient per acre.
[27]
New Biological Seed Treatment
Fungicide Increases Peanut Yields
P.A. Baclakman, J.T. Turner,
M.A. Crawford, and R.P. Clay
SEED treatment fungicides have been a
standard component of peanut disease control
recommendations for many years. These
fungicides are applied to prevent seedborne 
fungi
from rotting the seed, and to protect the emerging
seedling from fungi living in the soil. However,
they provide virtually no benefit beyond two
weeks after planting.
Alabama Agricultural Experiment Station
(AAES) studies have been conducted to evaluate
a new seed treatment that contained a bacterium
called Bacillus subtilis. Results of the study
showed that farmers who used the bacteria-treated
seed had average yield increases of more than 8%.
Furthermore, yield increases were more than 15%
for 17% of the farmers.
When the AAES study began in 1980, peanut
seed treated with this product produced 
seedlings
that emerged sooner and lapped the row sooner
than did plants developing from seed treated 
with
the traditional chemical fungicides. In addition,
the bacteria could be mixed with chemical seed
treatments without being killed, and 
the
commercial product had excellent shelf life, 
unlike
the nitrogen-fixing bacteria.
In 1982, researchers began to better understand
what was happening to the more vigorous 
peanut
plants. Early emergence was probably a 
growth
response to a hormone produced by the 
bacteria.
However, the faster growth of plants and 
the yield
increases were probably because of healthier 
roots
(Table 1). The bacteria were found growing 
on
the roots throughout the life of the peanut 
plants,
while the peanut plant itself had a healthier 
root
system with less Rhizoctonia and Fusarium
damage. The Bacillus subtilis organism applied 
to
the seed is known to produce several antibiotics.
The antibiosis that probably results following
successful root colonization, plus the competition
with pathogens for growth sites, apparently serves
to protect the peanut root system from several
root-rotting fungi. Improved yields are caused by
these healthier roots.
Studies were conducted during 1982 and 1983
to determine which peanut farmers would benefit
from this bacterization procedure, and how often
this would translate into a significant economic
benefit. These comparisons were made throughout
the Southeast with randomly selected farmers
growing treated seed (bacteria plus standard seed
treatment fungicide) in side-by-side comparison
with seed treated only with the standard fungicide.
Results of this experiment indicated that
approximately 60% of the farmers who used the
bacteria-treated seed had yield increases of more
than 5%, while 17% of the farmers had yield
increases of more than 15% (Table 2). When all
of the approximately 24 locations were averaged,
the yield increase for Bacillus-treated peanuts was
8.3%. Only one case of a reduced yield was
reported. Farmers who grew either peanuts or
soybeans in either of the previous two crop 
years
averaged 12.3% increases in yield, while farmers
who had no history of these crops in the previous
two years reported only a 3.4% yield
improvement.
The bacterial preparation, which will be
marketed under the name Kodiak?, was
remarkably capable of colonizing peanut roots.
All treated seed resulted in successfully colonized
roots. Lack of yield response was caused by
lower levels of fungal disease on the root systems
of nontreated plants, not by lack of colonization.
Peanuts that showed an obvious vigor response
almost always recorded considerably improved
yields. However, many peanut tests that did not
show vigor differences still resulted in improved
yields for the Bacillus-treated peanuts.
Peanut fields most likely to benefit from the
practice are those that have two-year or less
rotations of peanuts or soybeans or both. If
peanuts are planted before May 10 on these poor
rotations, yield improvements will be even more
pronounced. Bacillus subtilis is presently sold for
use on peanuts and cotton under the tradenames
Kodiak and Quantum?.
Backman, Turner, Crawford, and Clay, Department
of Plant Pathology.
[28]
TABLEa 1. EiFscm OF BAcTERIA APPLIED TO SEED ON RooT DISASE AND YIELD OF PEANUTS, 1982
Strain Root Yield! Increase
rot' acre
Lb. Pct.
No bacteria ................................................................... 2.45 2,171-
Bacillus subtiis
No antibiotic ............................................................. 2.68 2,264 + 4.2
Antibiotic producer...................................................... 2.14 2.541 +17.0
'Scale of 1 to 5: 1 = no disease, 2 = 25% rotted, 3 = 50% rotted, 4 = 75% rotted, and 5 = 100% rotted.
TABLE 2. YIELD EFFECrE OF PEANUT SEED TREATED WrM- BACILLUS SUBTIS SPORES AND FUNGICIDE AS COMPARED TO FUNGICIDE
ALON, 1983
Previous date Legumes in either of No legumes in
previous 2 years previous 2 years
Early .................................................................................... (6)' (2)
(before May 10)...................................................................... + 15.2% + 3.0%
Late..................................................................................... (5) (3)
(after May 10)........................................................................ + 8.7% + 3.7%
Weighted.................................................................................. (1 (5)
average
2 . . . . . . . .
** o00
.. . . . . . . . . .
000 to 0
. .
*
. . . . . . .
t 
. . . . 
9to*
.. . . . . . . . . . . . . . .
+ 12.3% +34
'( )parentheses indicate number of locations fitting the description.
2
At eight other locations there was a 6.3% increase in yield following bacterization by Bacillus subtilis.
SM-9 Spray Adjuvant and Control of
Southern Stem Rot of Peanuts
A.K. Hagan and J.R. Weeks
IN lATE winter 1992, the spray adjuvant
SM-9 was being marketed to Alabama peanut
producers for the control of white mold and
several other destructive diseases of peanut.
Claims of white mold control were based solely on
a single laboratory study and several farmer
testimonials. Extensive field research information
documenting the activity of SM-9 against any
peanut disease does not exist. Finally, SM-9 is
not registered as a pesticide in accordance with the
requirements of FIFRA and can only be marketed
as a surfactant. A study was conducted to
determine if SM-9 spray adjuvant had any effect
on white mold and yield of peanuts.
Trials were conducted in two rain-fed fields in
Henry County that had a history of white mold
damage. Florunner peanuts were planted in late
April. and maintained according to Alabama
Cooperative Extension Service recommendations.
Fungicides were applied by hand using a
backpack sprayer on the dates listed in the table.
Hit counts were made the day after digging, and
the plots were harvested with a combine.
SM-9 spray adjuvant did not protect peanuts
from white mold. The numbers of white mold hits
were similar in the plots treated with SM-9 and
the nontreated control plots. On the other hand,
two or four sprays of Folicur? and a single
application of Moncut? gave excellent disease
control. In addition, considerable foliar burn on
the newer peanut leaves was seen in both fields
after each application of SM-9. No damage to the
[29]
foliage was seen in the plots sprayed with Folicur
or Moncut.
Yields from the SM-9 treated plots also were
similar to those from the nontreated plots. Yields
from all other fungicide-treated plots were
considerably higher than those in the SM-9 or
nontreated control plots. Greatest yield increases
occurred in the plots treated with two or four
applications of Folicur or a single application of
Moncut.
In this trial, SM-9 surfactant had no effect on
white mold or on peanut yield. Based on these
results, Alabama peanut growers are advised not to
use SM-9 as an alternative to registered products
for the control of white mold on peanuts. EPA
registration of Folicur and Moncut for the control
of white mold on peanut is pending. Both of
these fungicides were very effective and should
have significant impact on peanut yields in fields
with a history of serious white mold damage.
Hagan, Department of Plant Pathology; Weeks,
Department of Entomology.
EFFECr OF SM-9, MONCUT, AND FOLICUR ON WHITE MOLD AND YIELDS OF PEANUT, 1992
Treatment and rate/acre Spray date(s) No. hits/100 Yield
row ft. lb./acre
Folicur 3.6F, 8 fl. oz ....................................................................... July 27 8.1 3,729
Folicur 3.6F, 8 fl1. oz ....................................................................... July 14, July 27 2.1 4,584
Folicur 3.6F, 8 fl. oz ....................................................................... July 1, July 14 .3 4,579
July 27, Aug. 4
Moncut 50W, 2 lb.......................................................................... July 14 1.9 4,469
SM-9, 1 pt ............................................................................. July 1, July 14 17.3 2,923
July 27, Aug. 4
Nontreated control ............................................................................. ----- 
19.4 3,236
LSD (P=0.05) 3.2 355
Fungicide-Nematicide Seed Treatment
Combinations:
Results and Potentials
PA. Backman and R. Rodriguez-Kibana
TO CONTROL nematodes, row crop farmers
in the Southeast routinely apply nematicides as a
separate operation at planting time. In addition,
peanut farmers apply systemic insecticides in
planting furrows for thrips control. The
development of a technique for the simultaneous
application of nematicide, insecticide, and
fungicide-treated seed would reduce farm
operations and resultant soil compaction.
Studies were conducted through the Alabama
Agricultural Experiment Station to develop a
treatment that could provide control of seedling
disease, early-season insects, and nematodes with
a minimal amount of labor and chemical inputs.
Tests were conducted on Florunner peanuts
using several systemic nematicides or insecticides.
Treatment rates were adjusted to deliver in-furrow
rates of approximately 0.5 lb. per acre using the
seed as the vehicle (Table 1).
Furadan? and Nemacur? depressed emergence
only slightly, and peanuts in general (Table 2)
showed very little phytotoxicity. Although
nematodes were not a problem in the peanut test
area, thrips damage was assessed and found to be
sharply reduced in the presence of Orthene? or
DS-15647? (Table 2). For both chemicals,
however, higher levels of phytotoxicity were
observed than for Furadan.
[30]
These data indicate that nematicides can be
coated on seed without excessive damage to the
seed and seedling, and that biologically active
rates of nematicides can be coated onto the seed
and still be compatible with seed treatment
fungicides. These studies have revealed treatments
that are good nematicides and others that are good
insecticides. As yet, the combination effect has
not been achieved.
Backman and Rodrfguez-Kdbana, Department of
Plant Pathology.
TABLE 1. EVF=S OF FUNGICIDE-NEMAICIDE COMBINATIONS ON PEANUT SEEDUNG EMERGENCE
Emergence
Nematicide used, rate/acre
1973 1974
Fungicide only 58.5 56.0
F . ....... 25 g54.6 52.2
Nemacur 95% tech, 250 ml .............. ............. 53.3 52.5
DS-15647, 160 ml ........ ..... ..... .......... ............................... -- 47.3
Orthene 80 SD, 132 g..***....#00.. . ... . . ...00 f 0*06" o.*0.-6. . ..0038.5
TABL.E 2. EFPBCrs OF NMxrcIDs iN COMBINATION WrIH SEED FUNGICIDES ON SEEDuNG EMERGENCE, NEMATODE POPULATIONS, AND
TIIIUPS DAMAGE IN FLORUNNER PEANUT
Nematicide used, rate/acre 
Emergence Total Thrips 
2
nematodes'
Pct.
Fungicide only............................................................. 56.0 187 43
Furadan 75, 225 g..........................................................52.2 go** 000 000 00 131 3.8
Nemacur tech., 250 ml..... ....... . ........................................................... 52.5 86 3.2
Orthene 80 SD, 160 ml ............................................ ......... ........................... 38.5 147 1.4
DS-1564127 ........ *13200*00g.0....."00000000.. . .... 00.....no......0.47.30 6000 00 og 00 00000140500 72.05 o
'Total nematodes per pint of soil from root region.
2
Severlty rating from 1 = no damage to 5 = severe leaf cupping and chlorosis.
Peanut Follar Fungicides: Relationships
Between Leafspot Control and
Kernel Quality
J.M. Hammond, P.A. Backman,
and J.A. Lyle
TE EFFECTIVENESS of foliar fungicides
for control of peanut leafspot was evaluated from
1971 to 1974 through the Alabama Agricultural
Experiment Station.
Benlate?, Bravo?, Duter?, and Kocide 404-
S? were applied at recommended rates using a
conventional ground sprayer at 14-day intervals.
Leafspot severity was rated by determining percent
defoliation and infections. All fungicide-treated
plots had less defoliation and infection than the
nontreated control plots (Table 1). Kernel quality
was determined using Federal-State Inspection
Service procedures. Plots sprayed with Bravo had
slightly better quality kernels than those from any
other fungicide treatment. However, kernels
harvested from the nontreated control plots had
significantly better quality than those from the
[31]
Bravo treatment. Kernels harvested from the
Benlate and Kocide 404-S treatments were slightly
inferior in quality compared to the Bravo
treatment, although not significantly. Kernels
from the Duter-treated plots were significantly
inferior in quality to those from plots treated with
other fungicides (Table 2).
These data indicate two possible mechanisms
for kernel quality effects: (1) maintenance of a
complete foliar canopy and (2) a direct toxin
action effect of the fungicide on soilborne fungi.
The maintenance of a relatively complete foliar
canopy made at least three major changes in the
ecology of soilborne fungi: (1) fewer leaves were
lost to the soil surface to serve as an organic food
source; (2) pesticides were filtered from the soil
surface by the "umbrella effect" of the canopy; and
(3) an altered subcanopy environment was created
that may stimulate certain soilborne fungi.
If a direct toxin action of the fungicide on
soilborne fungi was responsible for the
deterioration of kernel quality, one would expect
kernels of superior quality from plots where the
fungicide exhibited toxicity to the pathogenic
fungi, but little or no effect on the natural
antagonists. Inferior quality kernels would be
found in plots where fungicides exhibited toxicity
to the antagonists, but with little or no effect on
the quality deteriorating pathogens. Several
observations support this hypothesis. First, similar
levels of defoliation were obtained when Benlate,
Duter, and Kocide 404-S were used to control
leafspot (Table 1). However, use of Duter resulted
in significantly inferior kernels when compared to
the other two fungicides giving similar leafspot
control (Table 2). Secondly, when values for
kernel quality were examined, the control had a
significantly higher dollar value per ton than any
of the fungicide treatments.
If peanuts from the control plots are of better
quality and a true inverse relationship exists
between leaf maintenance and kernel quality, the
Benlate- or Kocide-treated plots, which had the
least defoliation, should have the most inferior
kernel quality of the fungicide-treated plots.
Peanuts from Benlate and Kocide-treated plots
were not significantly inferior in quality to peanuts
from Bravo-treated plots.
A third indication that a toxic action of the
fungicides altered the geocarposphere was
observed with the fungicide Benlate. Benlate was
extremely effective as a leafspot control fungicide
in 1971 and 1972. However, in 1973, the
pathogen developed resistance to this fungicide
and during the 1974 season disease severity in the
Benlate-treated plots was nearly equal to that of
the control (Table 1). Comparisons of quality data
for Benlate-treated plots over the four-year period
showed no improvement in kernel quality as
defoliation levels increased (Table 2). While not
conclusive, these observations indicate that a direct
toxic effect of a fungicide on a natural antagonist
(or pathogen) is more important to kernel quality
than the degree of leaf maintenance and the
canopy, although they are interrelated.
It is important to realize that even though
regular fungicide treatments for control of leafspot
result in inferior quality peanut kernels, the
tremendous yield increase resulting from the use
of these fungicides dictates their continued use in
the Southeast (Table 3).
Hammond, Backman, and Lyle, Department of Plant
Pathology.
TABLE 1. DEFOLIATION LEVEL (%) OF ARACmR HYPOGAEA L CAUSED BY CERCOSPORA SP. IN LEAFSPOT CONTROL TEST, 1971-1974
Treatment 1971 1972 1973 1974
Control .............................................................................................. 79.9a 53.0Oa 44.Oa 64.4c 
59.3a
Bravo 54 F ....................................................................................... 43.4c 6.4d 5.8bc 
15.0Od 22.7c
Benlate 50 WP ................................................................................... 24.8d 5.3d 6.1bc 55.1b 17.5d
Duter 47 WP ..................................................................................... 50.2bc 18.5b 12.4b 33.1d 
30.3b
Kocide 404-S (27 + 15) F .............................................................. 56.3b 12.1c 2.6c 18.7d 20.7cd
Values within columns followed by the same letter are not significantly different at the 5% level using Duncan's Multiple Range
Test.
[32]
TABLE 2. KERNEL QUALTY VALUES OBTAINED FROM PEANUT (ARACHIS HYPOGAEA L) LEAFSPOT 
CONTROL TEST, 1971-1974
1971 1972 1973 1974 X
Treatment Rate/acre
Dol. value/ton
Control ..................................... 0.0 304.90 296.73 298.60 409.43 327.03a
Bravo 54 F .................................................... 1.5 pt. 301.40 290.92 277.21 398.45 
316.56b
Benlate 50WP ............................................ 6.0 oz. 297.32 281.66 268.55 268.55 310.64b
Duter 47 WP ............................................. 6.0 oz. 298.87 284.79 239.68 239.68 298.33c
Kocide 404-S (27 + 15) F ........................ 2.0 qt. 301.15 299.27 291.63 291.63 312.94b
Values within columns followed by the same letter are not significantly different at the 5% level of probability using Duncan's
Multiple Range Test.
TABLE 3. YIELD, QUALrTY, AND VALUE PER ACRE OBTAINED FROM PEANUT LEAFSPOT CONTROL TEsTs, 1971-1974
Treatment Rate/ Yield/ Value/ Value/
acre acre ton acre
Lb. Dol. Dol.
Control ............................................................................ ........................... 0.0 2,558d 327.03a 418.27d
Bravo 54F ................................................................................................. 1.5 pt. 3,889a 316.56b 615.55a
Benlate 50OWP ................................................................ ......................... 6.0 oz. 3,286c 310.64b 510.38c
Duter 47WP .................................................................. .......................... 6.0 oz. 3,433bc 298.33c 512.08b
Kocide 404-S (27 + 15) F ...................................................................... 2.0 qt. 3,592b 312.94b 561.88b
Values within columns followed by the same letter are not significantly different at the 5% level of probability using Duncan's
Multiple Range Test.
Control of Peanut Soilborne Diseases May
Afford Yield Breakthrough
P.A. Backman
IMPROVED management practices by
Alabama growers have increased state peanut yield
averages by almost 1,500 lb. per acre since 1970,
to a current level of nearly 3,000 lb. per acre.
Despite this increase, yield losses of 20-30% to
soilborne diseases, such as white mold, limb rot,
pod rot, and root rot, still occur statewide.
Currently, available fungicides provide only 40-
60% control of these diseases, but Alabama
Agricultural Experiment Station tests indicate more
promising materials are on the way for peanut
growers.
Spotless? and Folicur?, nonlabeled triazole
fungicides, have provided leafspot control similar
to Bravo? for several years, when applied in a
season-long schedule. Because of their activity on
fungi that cause white mold, limb rot, pod rot, and
root rot, peanuts from fields treated with Spotless
and Folicur routinely outyielded peanuts from
Bravo-treated fields by 400 to 1,200 lb. per acre.
Since development of fungicide tolerant strains
of fungi has occurred where other triazole
fungicides have been used, Auburn researchers
also evaluated alternative treatment schedules that
will allow growers to benefit from soilborne
disease control from the triazole materials, but also
utilize Bravo during times of the season when
leafspot is the only problem. Additional benefits
are to delay development of resistance to the
triazoles and to reduce the overall cost of the
fungicide program. Bravo is likely to be less
expensive than the new triazole fungicides.
Research on midseason applications of Spotless
and Folicur indicate that both fungicides do an
excellent job of controlling white mold, either
when banded as granules over the row or directed-
sprayed onto the crown of the peanut plant (Table
2). Since the product is delivered in a narrow
band where white mold is most active, disease
control is achieved at lower use rates than when
[33]
the same products are applied broadcast with a
leafspot sprayer.
Flutolonil (Moncut?) is a relatively new
compound that may have experimental use
registration in 1994. When used for soilborne
disease control, this product can be mixed with
Bravo and applied with a leafspot sprayer, can be
banded sprayed as was done with the triazoles, or
can be applied as a granule. Unlike the triazole
fungicides, there is no effect on peanut leafspot.
In all cases, it has been highly effective in
controlling white mold and suppressing the
Rhizoctonia-induced diseases. Yields have often
been improved by more than 1,000 lb. per acre in
fields with only moderate disease severity (Table
3).
All of the fungicides tested and reported here
have activities to several soilborne diseases. It is
not always possible to quantify their impact on
each disease nor to tell if these represent all of the
fungi that are being controlled. These fungicides
are highly active on a group of fungal diseases
that are largely ignored by peanut farmers in the
Southeast. These new fungicides should
dramatically increase the profitability of peanut
production, despite an estimated $30 to $40 per
acre cost.
Backman, Department of Plant Pathology.
TABLE 1. EFFECTS OF FULL-SEASON SPRAY PROGRAMS ON PEANUTr YIELDS AND WHITE MOLD
Yield, lb./acre White mold (hits/40 ft. row)
Treatment'
1984 1985 1986 1987 Av. 1984 1985 1986 1987 Av.
Bravo, 1.1 lb ..................................... 4,737 3,666 3,763 2,459 3,656 7.0 2.0 5.7 18.0 8.2
Spotless, 0.12 lb ............................... 5,944 4,167 4,054 3,497 4,415 .7 1.0 2.8 3.7 2.1
Folieur, 0.22 lb .................................. 5,917 4,589 4,380 3,545 4,608 .2 .3 4.0 6.3 2.7
'All rates in lb. active ingredient per acre.
[34]
TABLE 2. EFFECS OF ONE APPLICATION OF FUNGICIDES' AT TWICE THE RATE USE) FOR CONTROL OF PEANur LEAFPOT
Soilborne diseases
Yield, lb.facre
1985 1986
Tetet1985 1986 1987 
Av. White Pod White Pod 
White o
mold rot mold rot mold o
No treatment ..................................... 2.650 2,750 3,001 2,800 6.5 
3.6 6.2 4.0 1 0.2^ 3.
Terraclor, 10 lb................................... 3,129 3,513 3,448 3,363 6.0 
3.5 3.0 2.9 4.2 2.
Spotless, 0.25 lb ................................. 4,015 3,436 4,144 3,865 
.8 3.0 4.0 2.9 2.4 2.
Folicur, 0.44 lb................................... 3,583 -- 3,583 1.5 2.4
'Applied in a 12- to 16-in, band at pegging over the row, using either a granule or directed (crown) spray.
TABLE 3. YIELD RESPONSE OF PEANUTS FOLLOWING TREATIENT WITH FLUTOLONIL FUNGICIDE
Yield, lb./acre White mold (hitsf40 ft. row)
Treatment'
1985 1986 1987 Av. 1984 1985 1986 
1987 Av
No treatment......................................... 2920 2,520 3,001 2,814 
4.0 5.1 13.5 11.58.
Terraclor, 10 lb ..................................... 3,294 3,513 3,448 3,418 
2.7 1.9 6.2 3.93.
Flutolonil, 1.0 lb..................................... 3,219 3,775 4,586 3,860 
1.1 1.9 5.7 3.02.
Flutolonil, 2.0. lb.................................... 3,763 3,674 4,876 4,104 
1.0 1.5 5.8 1.02.
'All rates in lb. active ingredient per acre.
w
:11
i
Viruses Infecting Peanuts
R.T. Gudauskas, K.B. Burch, P. Jin,
A.K. Hagan, and J.R. Weeks
A STUDY was conducted from mid-July to
mid-August in 1990 and 1991 to determine the
identity and distribution of the major virus
pathogens of peanuts in Alabama. Leaves from
peanut plants showing virus-like symptoms were
collected from fields selected at random in the 14
counties making up the major peanut production
area. Symptoms on suspect virus-infected plants
included leaf chlorosis, mottling, necrosis, line
patterns, and distortion, as well as overall plant
stunting. Leaf samples also were taken in most of
these same fields from plants showing no apparent
symptoms. Sap was extracted from all samples
and tested for peanut mottle virus (PMV), peanut
stripe virus (PStV), peanut stunt virus (PSV), and
tomato spotted wilt virus (TSWV) by bioassays on
indicator plants in the greenhouse, and by enzyme-
linked immunosorbent assays in the laboratory.
A total of 1,883 peanut plants from 158 fields
throughout the 14-county area were assayed for
viruses during the 1990 and 1991 growing seasons
(see table). PMV and TSWV, singly or in
combination, were identified in every county and
generally at high frequencies in most counties.
PSV was found in all but one of the counties, but
at a much lower frequency. PMV and TSWV
were detected in samples from a majority of the
fields in all 14 counties. PSV was identified in
about one-fourth of the fields surveyed, but these
fields were in 13 counties. No other viruses,
including PStV, were identified in any sample
during the two-year period.
These results show that PMV and TSWV were
prevalent throughout the peanut production area,
and that PSV occurred at lesser, but significant
levels as well. Generally, incidence of all the
viruses was higher than was previously suspected.
The impact of these viruses on the peanut crop in
Alabama has not been determined; however, their
potential for causing serious losses has been well
documented in other states.
Gudauskas, Burch, Jin, and Hagan, Department of
Plant Pathology; Weeks, Department of Entomology.
VIRusES IDENTIFIED IN PEANUT PLANTS DURING 1990 AND 1991 GROWING SEASONS IN ALABAMA
Plants infected with:
County Fields Plants
Barbour ............................................................ 12 136 40 1 47 17
Bullock ............................................................ 8 114 50 4 34 27
Butler ............................................................... 6 79 11 0 7 2
Coffee .............................................................. 17 111 25 1 23 10
Conecuh .......................................................... 7 108 27 14 39 12
Covington ....................................................... 10 121 36 1 20 6
Crenshaw ........................................................ 7 73 26 4 27 21
Dale ................................................................. 12 149 24 3 55 16
Escambia ....................................................... 7 80 25 12 43 14
Geneva ............................................................ 16 214 56 14 91 37
Henry ........................................................... 19 239 70 6 96 34
Houston .......................................................... 18 183 48 4 44 20
Pike .. 1..:. .... ..................................... 12 167 31 19 46 18
Russell............................................................... 7 109 10 8 27 2
Totals ............................................................... 158 1,883 479 91 599 236
'Total of all single and mixed infections with this virus.
[36]
INSECTS
Pheromone Traps Inadequate for
Sampling Lesser Cornstalk Borer
T.P. Mack and C.B. Backman
ACCURATE sampling of lesser cornstalk
borer in peanuts is critical since damage in heavily
infested fields can exceed 70%. Larvae feed
inside stems and usually live underground, making
sampling at this stage difficult and time
consuming. Sampling adult moths, which have
distinctive size, shape, and coloration
characteristics is an alternative being tested at the
Alabama Agricultural Experiment Station.
Commercially available pheromone traps that
contain a flypaper-like adhesive and a chemical
sex attractant were used to trap lesser cornstalk
borer moths. Based on on-site sampling of adult
moths by trained entomologists, the traps have
been unreliable in monitoring large population
increases of this pest.
Field studies were conducted at the Wiregrass
Substation, Headland, in 1984-86 in conventionally
tilled and planted Florunner peanuts. Four
pheromone traps per field were examined twice
weekly throughout the growing season each year.
The pheromone source (a chemically impregnated
rubber septum) was changed weekly, and sticky
traps were changed when approximately 100
moths were captured.
The number of male moths per trap per night
was compared to the number of moths per yard of
row determined by flushing moths from peanut
plants. Two people each used a yardstick to
agitate peanut plants in two 300-ft. rows, and
researchers identified and counted the number of
moths flying from the disturbed plants. Flushing
was conducted weekly at dawn, when adult moths
are still active.
Few adults were found in weekly flush
sampling in 1984 and 1985, which were years of
low lesser cornstalk borer populations. The
average number of moths flushed each week in
1984 and 1985 ranged from approximately 0 to
0.4 per yard. The population in the hot, dry
summer of 1986 was much greater than the
previous year's populations, and ranged from 0 to
1.2 moths per yard. Cooperative Extension
Service recommendations specify that insecticides
should be applied when fresh damage or larvae are
found on 30% or more of the plants in a field.
This threshold level was reached on June 2, 1986,
when the larval population, as determined by soil
sieving, was approximately one per yard. The
larval population eventually increased to more than
14 per yard on August 7, so the large adult moth
population did produce a large population of
larvae.
The number of male lesser cornstalk borer
moths per trap per night varied with time and year,
and ranged from 0 to 43. Male moth abundance
exceeded 20 per trap per night only three times
from 1984 to 1986, so moth abundance was
usually low. No pheromone trap catches exceeded
20 per trap night in the population outbreak year,
1986. Instead, trap catches fluctuated greatly from
date to date, ranging from 2.5 to 14.5 in August
1986.
The number of moths per pheromone trap per
night was statistically related to the number per
yard determined by flushing in only one of the
three years, and trap catches were not similar to
flush counts in the population outbreak year of
1986. In short, pheromone traps did not
accurately determine if a large number of the
moths were in a field. A possible explanation for
this result is that the sex attractant in the trap may
not be exactly the same chemical that a female
moth produces.
Pheromone traps are useful because they can
quickly inform growers of the presence of lesser
cornstalk borer moths. Presence of moths can
alert a grower of the need for scouting fields for
lesser cornstalk borer larvae. This information can
be important because, if no moths have been
caught in a trap for the previous 30 days, then the
chances are small that a large population of larvae
is present.
Mack and Backman, Department of Entomology.
[37]
Number/night
3 5
30
25
20
15
10
5
1 16 31 15 30 
14 29
July August September
Sample date
Abundance of lesser cornstalk borer adult males
from pheromone traps, 1984 to 1986.
Long-Lasting Granular Insecticide the
Most Effective Against Lesser
Cornstalk Borers
T.P. Mack
WHEN to apply granular insecticides to control
lesser cornstalk borers in peanuts often becomes a
balancing act for growers. Late applications 
may
allow larvae to damage peanuts before chemicals
are applied and too early an application may 
mean
the insecticide degrades and larvae damage
peanuts late in the season. Recent Alabama
Agricultural Experiment Station (AAES) research
indicates none of the currently available
insecticides consistently lasts the necessary 
60
days to provide adequate protection to pods.
Lorsban? provided 19 to 50 days of 
control
against infestations of 
lesser cornstalk borers,
depending upon environmental conditions, and was
consistently the longest lasting insecticide
available.
Since there are no insecticides to protect
peanuts for the 60-day duration of time that lesser
cornstalk borers may feed on the crop, time of
application of available materials is critical. It is
equally critical for growers to know how long
these insecticides remain toxic to this insect.
However, determining length of effectiveness of a
soil insecticide against a pest insect is challenging,
because of movement of the pest, predation and
disease impact on pest abundance, and the effects
of soil temperature and moisture on pesticide
degradation. A bioassay developed by the AAES
allows researchers to overcome many of these
problems and determine the length of effectiveness
of several common granular insecticides against
the lesser cornstalk borer.
[38]
Only 1986 had an outbreak
1984
1985
1986
1 I -
- I " l I '
u1 16
June
A
Experiments were conducted at the Wiregrass
Substation, Headland, in conventionally tilled and
planted Florunner peanuts in 1988 and 1989.
Plots were eight rows wide by 50 ft. long.
Treatments consisted of a nontreated control, and
each of the following granular insecticides:
Lorsban, Dyfonate?, XRD-429?, Mocap?,
Force?, and Fortress?. Of these materials, only
Lorsban and Dyfonate are labeled for use on
peanuts. Insecticides were applied with a small-
plot granular applicator.
The length of effectiveness of each insecticide
was determined in the laboratory by collecting soil
from each field plot and by exposing small larvae
to it. One soil sample was collected from each
plot about every two weeks. Each sample was
collected by taking a 12-in.-wide by four-in.-long
by one-in.-deep subsample from three randomly
selected rows within each plot. The biweekly
collection of soil from the field allowed
researchers to determine the length of effectiveness
of each insecticide since the collected soil had
been exposed to the same conditions as normal
soil in the field.
Toxicity was evaluated as follows: Small
larvae were placed in two-oz. plastic cups that
were filled with a sample of field-collected soil to
a depth of 0.5 in. Sorghum seedlings were placed
in each cup as a food source for the larvae. Cups
were kept in a controlled environment chamber for
the assays, and the number of living larvae in each
cup was determined at 72 hours. An effective
treatment was defined as a treatment that
decreased the percent survival of larvae compared
with that of larvae exposed to nontreated soil.
Treatment effectiveness was evaluated for each of
the biweekly sampling dates.
In 1988, 59% to 85% of larvae survived a 72-
hour exposure to soil from nontreated plots.
Dyfonate and Lorsban were the only treatments
that reduced larval survival at five days after
application. Only Lorsban reduced survival at 19
days after application. No treatments reduced
larval survival at 33 days after application.
Results in the table show that survival of larvae
in nontreated soil in 1989 ranged from 78% to
96%. Lorsban, XRD-429, and Dyfonate reduced
larval survival at 6, 19, and 25 days after
application. Lorsban was the only insecticide
tested that reduced larval survival at 39 and 53
days after application, and it was the only
insecticide that was effective for more than 14
days in both years of the test.
Mack, Department of Entomology.
AVERAGE PERCENTAGE SURVIVAL OF LESSER CORNSTALK BORER LARVAE EXPOSED TO INSECTICIDE-TREATED SOIL IN
ALABAMA, 1989
Survival by days after treatment, pet.
Treatment,
Insecticide a.i./acre 0 6 19 25 39 53
Nontreated ..........................................................-- 78 93 96 96 89 81
Lorsban 15G ........................
................. . . . . .. ... ....  
2.0 lb. 4 7 0 0 4 29
XRD-429 2G ...................................................... 1.0 lb. 11 30 37 37 85 81
Dyfonatel0G
1 
.......................
................ . . . . ..........  
2.0 lb. 7 0 14 33 88 78
Force 1.5G .......................................................... .3 lb. 26 59 33 81 78 88
Fortress 10G ........................................................ 5 lb. 0 33 81 81 85 88
Mocap 15G ......................................................... 3.0 lb. 74 85 89 78 85 89
'Labeled for use on peanuts.
[39]
Why Are Lesser Cornstalk Borers a Hot
And Dry Weather Pest of
Alabama Peanuts?
T.P. Mack and C.B. Backman
THE LESSER cornstalk borer is a major insect
pest of peanuts in Alabama, with damaging
population outbreaks typically occurring in hot,
dry weather and on sandy soils. In the drought
plagued season of 1980, lesser cornstalk borers
caused more than $43 million in damage to peanut
crops in Alabama, Georgia, Oklahoma, and Texas.
Why these outbreaks are more severe in hot, dry
weather is being studied at the Alabama
Agricultural Experiment Station as part of a
research project to develop a microcomputer-based
model that predicts when damaging populations of
lesser cornstalk borers occur. To do this, the life
cycle of the lesser cornstalk borer was studied in
detail.
Eggs of the insect are laid singly within 0.25
in. of the soil surface under the peanut canopy.
Newly hatched larvae crawl across the soil from
the oviposition site and feed on a peanut plant or
other edible organic matter. Larvae spend most of
their time below the soil's surface and construct a
silken tube interwoven with soil particles, which is
attached to the plant. Pupation occurs in the soil
from which adult moths emerge. Female moths
appear to lay eggs only at night, and may spend a
significant amount of time away from peanut
fields.
Since lesser cornstalk borers are cold-blooded,
temperature changes affect their rate of growth and
development. The growth rate and hence the
feeding rate of lesser cornstalk borers are
temperature dependent, with hot weather greatly
increasing lesser cornstalk borer feeding.
Lesser cornstalk borers spend most of their life
cycle as larvae. This stage lasts 455 F degree-
days. The lower developmental threshold for
lesser cornstalk borers is 59?F, so it would take 13
days with an average daily temperature of 94?F
[(94 - 59) x 13 = 455] for a newly emerged lesser
cornstalk borer larvae to reach pupation. An
average air temperature of 940 F would be difficult
to achieve, since it would require a daily
maximum of 112?F and a minimum of 76?F [(112
+ 76) + 2 = 94]. These are soil temperatures,
however, that can be reached in July and August
when peanuts begin to wilt from lack of moisture.
Leaves of a wilted peanut plant droop when
under moisture stress, allowing more sunlight to
reach the soil's surface. This significantly
increases soil temperatures, which in turn will
increase the growth and feeding rate of any lesser
cornstalk borer larvae in the soil. So, lesser
cornstalk borer larvae could be feeding at their
greatest rate when a peanut plant cannot withstand
significant damage.
Temperature was found to also affect the
number of eggs laid per adult female lesser
cornstalk borer. In a laboratory study at Auburn,
adult females laid two times more eggs, at a two
times faster rate when they were held at a constant
temperature of 89?F, compared to those held at a
constant temperature of 72
0
F. Thus, hot
temperatures are conducive to the laying of a large
number of lesser cornstalk borer eggs.
High soil moisture has been known to inhibit
the development of lesser cornstalk borer
populations, but the mechanisms for this have,
until recently, been unknown. Research has
shown that small larvae emerged from the soil
when it was moist, and either stayed on the soil's
surface or attacked the plant above the soil line.
This behavior exposed the larvae to predators,
such as striped earwigs and fire ants. Soil
moisture-holding capacity is directly related to soil
type, with sandy soils having the least soil water-
holding capacity. Thus, sandy soils dry out the
fastest, indicating that small lesser cornstalk borers
in sandy soils would be exposed to predation less
than those in soils with a high clay content.
Soil moisture may also affect oviposition.
Lesser cornstalk borers laid 98% of their eggs in
the soil when it was dry and only 55% in wet soil.
The other eggs were laid on the plant, where they
would be exposed to egg parasites and predators.
So, why do lesser cornstalk borer outbreaks
occur in hot and dry weather, and typically on
sandy soils? It appears that the effects of
temperature on the total number of eggs per
female, the number of eggs laid per day, and the
growth and feeding rate of the larvae are
important. Also, the effects of soil moisture on
the behavior of small larvae and on the oviposition
site selection by the adults are important. Since
[40]
lesser cornstalk borers have two to four
generations during the peanut growing season, hot
Larvae
43%
Pupae
21%
and dry weather must coincide with a major moth
flight to produce a damaging outbreak.
Mack and Backman, Department of Entomology.
/ Eggs
9%
Mated Adults
25%
Unmated adults
2%
Life cycle of the lesser cornstalk borer showing percentage of total lifetime in any stage.
Lesser Cornstalk Borer Damage
to Peanuts
T.P. Mack, J.R Weeks,
and C.B. Backman
THE LESSER cornstalk borer is a key pest of
peanuts grown on sandy soils in the southeastern
United States, with damaging populations
occurring during hot and dry years. Yield losses
exceeding 70% have been reported in fields where
damaging lesser cornstalk borer populations have
developed. It is essential that lesser cornstalk
borer damage to leaf, flower, peg, pod, and seed
production be quantified so that growers know
when this insect is causing economic damage.
To quantify lesser cornstalk borer damage, a
two-year greenhouse study was conducted at the
Alabama Agricultural Experiment Station.
Florunner peanut plants potted in Dothan sandy
loam soil were infested with five densities of
lesser cornstalk borer larvae. Each plant had from
zero to eight larvae feeding on it for
approximately one month. Five different plant
ages were studied to see if peanut plants were
more susceptible to lesser cornstalk borer feeding
at (1) just prior to flowering, (2) flowering, (3)
[41]
early pegging, (4) early pod fill, or (5) late pod
fill.
The dry weight of peanut pods, seeds, and
roots decreased by an average of 6% for each
larva feeding throughout its larval life on the
plant. Lesser cornstalk borer larvae do not feed on
roots, but damage the root crown and reduce the
flow of sugars produced by leaves to the root
system. So, the lesser cornstalk borer affects the
entire plant, not just pegs and pods. This effect
did not change with plant age. A reduction in a
peanut plant's root system decreases its ability to
obtain nutrients from the soil and withstand
environmental stresses. This is critical because
damaging populations of the lesser cornstalk borer
often develop during a drought. When this
happens, water stress from both lesser cornstalk
borer damage and the drought could greatly reduce
peanut yield.
Based on the results of these studies, it appears
that in order for lesser cornstalk borer management
to be successful, control tactics must be employed
before many large-sized larvae are found in a
field. Insecticides applied after peg, pod, and root
crown damage has occurred will probably reduce
the lesser cornstalk borer larval population, but
economic damage will already have occurred.
Recommended granular insecticides applied when
most larvae are small to medium-sized will reduce
the larval population and prevent economic losses.
Rainfall should improve insecticide performance,
but is not needed to "activate" some of the
recommended granular insecticides, since lesser
cornstalk borers regularly crawl on the soil
surface.
Mack, Weeks, and Backman, Department of
Entomology.
Dry weight/plant
10
8
6
4
2
0
0 2 4 6 8
Lesser cornstalk borer density
Dry weight loss to peanuts from the lesser cornstalk borer.
[42]
-
g. aUndamaged pods
Undamaged seeds
Roots "
Lesser Cornstalk Borer And Aflatoxins
Are Double Trouble For Peanut Growers
T.P. Mack and KI.L Bowen
LESSER cornstalk borers and aflatoxins have
more in common than hot weather, according to
recent Alabama Agricultural Experiment Station
research. In tests at the Wiregrass Substation,
Headland, there was a close relationship between
damage by lesser cornstalk borers and visible
Aspergillus flavus, the aflatoxin-producing fungi
(94% correlation). However, the use of
insecticides reduced this correlation.
Aflatoxin-producing fungi are predominant in
the light soils in which peanuts are grown, and
occur most frequently when hot dry conditions
prevail. High temperatures favor growth of these
fungi, limit growth of competing organisms, and
stress peanut plants, making infection more likely.
Infestation of seed by aflatoxin-producing fungi
also is greater in peanuts that are damaged in any
way.
Hot and dry conditions also favor population
outbreaks of the lesser cornstalk borer. Larvae of
this insect feed on peanut root hypocotyls,
developing pegs, and pods, and can be a
devastating pest of peanuts. In feeding on the
developing pods, lesser cornstalk borers cause
extensive damage to pods and seeds. Thus, larval
feeding may provide a means of entry forA. flavus
into the peanut seed.
In a 1990 study, plant and insect samples were
collected from nonirrigated plots used in
insecticide trials on peanuts. All plots were
conventionally tilled and planted with Florunner
peanuts. Trials included a comparative insecticide
study and a study on the date of application of the
insecticide Lorsban?. Peanuts were planted on
May 7. On July 5, at early bloom, plots were
treated with Lorsban at two lb. active ingredient
(a.i.) per acre, Mocap? at three lb., Dyfonate? at
two lb., Fortress? at 1/2 lb., and Counter? at two
lb. Of these materials, only Lorsban and Dyfonate
are labeled for use on peanuts. Nontreated control
plots were left for comparison.
A second trial was planted on May 23 and
consisted of four treatments: a nontreated control
and Lorsban at two lb. a.i. applied either 30, 45,
or 71 days after planting.
Initially, larvae were collected from these field
trials to determine if the lesser cornstalk borer
carried aflatoxin-producing fungi. These larvae
were collected by uprooting plants and taking
larvae back to the laboratory. In addition, relative
abundance of lesser cornstalk borers was
determined with pitfall traps on a weekly basis
during the growing season. Incidence of
aflatoxigenic fungi was determined on several
dates in August and September by randomly
selecting and pulling five whole plants from which
10 pegs and 10 pods were removed. These pegs
and pods, once removed from plants, were surface
sterilized and incubated for three days, after which
aflatoxigenic fungi were visually identified by the
color and shape of the spores.
After harvest, peanut pods were collected from
experimental plots and rated on the occupance of
damage by lesser cornstalk borer, scarification and
other hull or pod damage, and presence of visible
aflatoxigenic fungi. Samples of harvested peanuts
were graded and incubated to determine if
aflatoxigenic fungi colonized peanut tissue.
Field-collected larvae did carry spores of
aflatoxin-producing fungi on their cuticles or
"skin," as well as 
internally. Additionally, 
as
lesser cornstalk borer populations increased in the
latter part of the season, incidence of A. flavus on
developing pegs and pods increased. In fact, in
peanuts that had not been treated with any
insecticide, where there was damage by the lesser
cornstalk borer, there were almost always
aflatoxigenic fungi present. This relationship
changed somewhat when insecticides were applied,
generally decreasing the apparent interaction
between these two organisms.
Peanuts treated with a single application of
Lorsban at 30, 45, or 71 days after planting had
consistently less damage by lesser cornstalk borer,
less visible A. flavus, lower levels of aflatoxins,
and greater yields (see table). Plants treated 45
days after planting (at flowering) had better grades
and yields than those in the other treatments.
Since it is currently not possible to treat a
peanut field with a fungicide for A. flavus, it is
important to understand the relationship between
contamination with this fungus and damage due to
lesser cornstalk borer. Such information may
[43]
provide growers the option of treating for an
infestation of lesser cornstalk borer, thereby
decreasing the risk of aflatoxin contamination in
peanuts.
Mack, Department of Entomology; and Bowen,
Department of Plant Pathology.
INCIDENCE OF POD DAMAGE AND FUNGAL OCCUPANCE, YIELD, AND TOTAL AFLATOXIN CONTENT IN PEANUTS FROM LORSBAN TIMING
TRIAL, 1990
Visible Scarification Observed Yield/acre Aflatoxin
Treatment LCB A. flavus level
damage
Nontreated ............................................................... 2.25 43.5 11.0 709 114
30 days after planting ............................................. 1.75 35.5 6.2 1,243 5
45 days after planting ............................................. 1.75 22.5 3.6 1,454 16
71 days after planting ............................................. 1.75 37.1 4.9 1,063 31
Granular Insecticides Harmful to
Beneficial Insects in Peanuts
T.P. Mack
GRANULAR insecticides are used to control
the lesser cornstalk borer in peanuts. There is a
great potential for destroying beneficial arthropods,
such as spiders and bigeyed bugs, because the
insecticides are applied during the growing season
when insects are present in fields. This should be
especially true of beneficial arthropods that live on
the soil surface, such as earwigs and fire ants,
where the granules are applied. It is very
important to maintain the abundance of beneficial
arthropods in peanut fields because they provide
free and effective control of many insect pests.
Destroying beneficials also increases the
abundance of some insects pest in other crops.
The effects of five granular insecticides on
beneficial insects were studied in a two-year field
study in conventionally planted and tilled peanuts
done in 1989 and 1990 at the Wiregrass
Substation, Headland. Goals of the study were to
compare the effects of several granular
insecticides, learn if any kill beneficial arthropods,
and determine if other pests increase in abundance.
Sunrunner peanut seeds were conventionally
planted in a Dothan sandy loam soil. Insecticides
used were Lorsban 15G? at two lb. active
ingredient (a.i.) per acre, Mocap 15G? at three lb.
a.i. per acre, Dyfonate 10G? at two lb. a.i. per
acre, Fortress 10G? at 0.5 lb. a.i. per acre,
Counter 15G@ at two lb. a.i. per acre, and a
nontreated control. Of these materials, only
Lorsban and Dyfonate are labeled for use on
peanuts. Beat sheets were used to sample for
insects living on the foliage of peanuts, and pitfall
traps were used for insects on the soil-surface.
Samples were taken for at least five weeks after
treatment.
Applications of granular insecticides had very
transitory effects on insect pests, such as the corn
earworm and fall armyworm. The applications
had no effect of beneficial arthropods in the
foliage such as bigeyed bugs and spiders (Table
1).
Predators such as striped earwigs and red
imported fire ants were the most abundant
beneficial insects. Abundance of these predators
declined in some treated plots for as long as one
month, which would increase the probability of
economic damage from insect pests such as the
lesser cornstalk borer (Table 2).
A potentially serious result of applying a
granular insecticide to peanuts is the observed
reduction of soil surface dwelling arthropods, such
has fire ants and striped earwigs. These two
predators were the most abundant arthropods
[44]
sampled, so the negative effects of granular cornstalk borer, but may also reduce 
the
insecticides could increase the probability of abundance of striped earwigs and 
imported fire
economic damage from the lesser cornstalk borer ants for the remainder of the growing 
season.
and other insect pests. This underscores the need
for timely applications of insecticides based on
scouting. Insecticides applied too early may not Mack, Department of Entomology.
only degrade and be ineffective against the lesser
TABLE 1. ABUNDANCE OF SELECTED PREDATORS BY TREATMENT COMBINED OVER ALL SAMPLE DATES, 1990
Insecticide Imported Bigeyed bugs
2  
Spiders Spiders Ground beetles
fire ants' (canopy)
2  
(soil-
dwelling)'
Nontreated ................................... 20.8 ? 3.1 0.8 t 0.2 0.2 ? 0.1 1.7 ? 0.2 3.9 ?t 0.8
Lorsban ........................................ 4.2 ? .9 .6 ? .2 .2 ? .1 1.2 ? .4 4.3 ? 1.0
Mocap .......................................... 7.3 ? 2.0 1.3 2 .5 .1 ? .1 1.3 ? .3 4.4 - 1.0
Dyfonate ...................................... 9.6 -? 2.5 1.0 ? .3 .3 ? .1 1.7 ? .3 4.5 - 1.1
Fortress ........................................ 8.8 1.5 1.1 ?, .4 .3 ? .1 1.7 ? .3 5.2 ? 1.2
Counter ........................................ 12.0 ? 1.8 .6 ? .2 .4 ? .1 1.0 ? .2 4.5 ? 1.0
'Number per trap per week from pitfall traps.
'Number per six row-feet per week, from beat sheets.
TABLE 2. ABUNDANCE OF STRIPED EARWIGS FOR 35 DAYS AFTER TREATMENT ON JULY 5, 1990'
Insecticide 5 12 19 28 35
Nontreated ..................... 14.9 - 5.1 8.6 - 2.4 23.0 ? 3.2 112.5 - 20.1 100.5 ? 11.1
Lorsban .......................... 3.9 ? 1.4 4.1 ? 2.0 13.1 ? 3.9 89.4 ?, 7.3 102.6 ? 9.2
Mocap ............................ 2.9 ? 1.2 5.3 ? 1.6 20.3 ? 2.9 90.9 ? 7.9 135.1 ? 3.0
Dyfonate .......................... 5.4 ? 1.4 6.6 ? 2.6 25.5 t 8.8 97.9 ? 18.7 133.1 ? 28.5
Fortress .......................... 1.5 ? .5 6.9 ? 3.3 36.8 ? 11.1 101.9 ? 12.5 132.1 ? 15.7
Counter .............................. 6 .3 2.1 ? 1.1 10.8 ? 2.8 89.0 ? 14.2 130.9 ? 10.3
'Number (average ? standard error) per trap per week, from pitfall trap samples.
[45]

MODELS AND PREDICTIONS AIDS
AU-PNUTS--AAES Developed Expert
System Helps Manage Peanut Pests
D.P. Davis, T.P. 
Mack,
R. Rodriguez-Kiibana, 
PA. Backman,
P.M. Brannen, and J.C. Jacobi
AN "EXPERT SYSTEM," which refers to a
program that uses the knowledge of human experts
to solve problems, is being developed by the
Alabama Agricultural Experiment Station to aid
Alabama peanut growers.
This system, known as AU-Pnuts, is being
designed to apply expert-like reasoning for
decision making when human experts are not
available. Most expert systems can even inform
the persons using them how a conclusion was
reached. Eventually, the user may learn how the
expert system arrives at decisions, which has the
added benefit of educating the user.
AU-Pnuts is an example of the many expert
systems being developed for use in agriculture.
This AAES-developed system is for managing
pests in peanuts, and was designed to be a
"planting-to-harvest" decision aid. Growers 
may
maximize profitability while reducing pesticide use
by using AU-Pnuts to (1) determine yield loss
from root-knot nematodes and identify profitable
alternatives for nematode control, (2) determine
most profitable timing of treatments for fungal
diseases, and (3) conduct cost/benefit analyses for
control of foliar feeding insects and the lesser
cornstalk borer. Management of these pests
requires knowledge of pest density, crop value,
costs of control, and weather conditions.
The expert system would inquire what the
previous crop was. If the previous crop was not
peanuts (or another crop on which these
nematodes survive well), then peanuts could be
planted without economic losses from nematodes.
If the previous crop was peanuts, then AU-Pnuts
would ask for the number of nematodes extracted
from a soil sample.
An equation has been developed that allows
prediction of yield loss based on nematodes in soil
samples. If this loss is greater than 600 lb. per
acre, then AU-Pnuts would recommend planting an
alternate crop. If the loss estimate was less than
600 lb. per acre, then it would recommend
planting peanuts. AU-Pnuts would also ask for the
cost of nematicides to determine whether they
should be used, and what alternative crops the
farmer could plant, to estimate the most profitable
rotational schemes.
AU-Pnuts has several important advantages
over other methods of decision making for pest
management. It recommends pesticide
applications only when they are economically
justified, so unnecessary applications will be
reduced. Further, AU-Pnuts integrates the
management of insects, diseases, and nematodes
into a single unit, since decisions made for one
pest affect almost all subsequent actions.
Control of leafspot disease is expensive for
Alabama peanut growers, usually requiring six to
eight sprays applied on a 14-day schedule. AU-
Pnuts uses environmental factors and history of
leafspot development on Alabama peanuts since
1980 to offer an alternative for this approach. Use
of AU-Pnuts successfully eliminated one or more
fungicide applications without reducing leafspot
control or yields in tests throughout the three U.S.
peanut belts.
Plant pathologists have long known that the
fungus that causes peanut leafspot requires
moisture to infect the leaf. Therefore, applications
made during dry periods are of little value when
leaves are not wetted by rain, fog, prolonged dews,
or irrigation water, within a period of about 10
days after the fungicide is applied. Additionally,
rotated peanuts usually need not be sprayed as
early in the growing season as peanuts planted
behind peanuts, since fungal spores from peanut
residue are not present. The end result is farmers
over-treating for leafspot because of the lack of a
system that advises a more appropriate timing for
leafspot control sprays.
To develop a set of rules to manage leafspot,
research was begun by looking at the progress of
the disease in Florunner peanuts in every year
since 1980. These studies indicated that rainfall of
[47]
0.1 in. or greater on any given day was a good
predictor of leafspot development. Close
examination of the data indicated that after six to
eight days with 0.1 in. of rain, disease begins to
develop quickly.
From this and a knowledge of disease
development, guidelines were developed and
tested, for the management of leafspot on
Florunner peanuts using chlorotholonyl (Bravo?,
Evade?, Terronil?, and Echo?) fungicides. The
only equipment necessary is a rain gauge that can
accurately measure 0.1 in.
For the use of these results the term "rain
event" means any day with more than 0.1 in. of
rain, or more than 0.1 in. of irrigation water, or
with a fog that begins before 8:00 p.m. If you
have plans to irrigate soon, the forecast for a rain
event is 100%.
A. TIMING FOR THE FIRST SPRAY OF THE
SEASON:
1. After plant emergence, begin counting the
number of rain events. Spray when six rain
events have been recorded, Or,
2. If leafspot is observed in the lower leaves of
the plant (two or more spots per plant), spray
immediately even if the number of rain events
in rule 1 has not been reached.
B. TIMING FOR SECOND AND ALL LATER
SPRAY APPLICATIONS:
1. Discontinue fungicide applications if you are
within 14 days of harvest. Or,
2. If you are more than 14 days from harvest,
wait 10 days after the previous fungicide
application, then begin counting rain events,
and checking the five-day weather forecast.
a. Even if no rainfall has occurred yet, if the
average rainfall probability for the next
five days is 50% or higher, spray
immediately. Or,
b. Spray after one rain event if the average
rainfall probability is 40% or greater for
the next five days. Or,
.. Spray after two rain events if the average
rainfall probability for the next five days
is 20% or higher. Or,
d. Spray when three rain events have been
recorded.
These rules were tested during the wet season
of 1989 and the dry season of 1990 on irrigated
peanuts at the Wiregrass Substation, Headland. In
both years the number of fungicide applications
was reduced without sacrificing disease control or
yield.
During the 1990 season, additional tests of this
system were conducted in Georgia, Florida, and
Oklahoma. In all locations, fungicide sprays were
reduced, requiring only three to five applications
(depending on irrigation timing and rotation) to
achieve a similar level of disease control and yield
as peanuts sprayed seven times on the standard
14-day program.
Results obtained on farms throughout the
peanut-growing region of Alabama indicate use of
AU-Pnuts leafspot module can result in better
disease control and higher yields for Alabama's
peanut farmers than calendar-based applications.
In 1991, on-farm studies were conducted with
seven peanut producers' in five counties in
Alabama. On-farm evaluations required
coordination and training of county agents and
volunteer producers. The National Weather
Service provided weather forecast information for
the predictive portion of AU-Pnuts, and this
information was delivered to producers via a toll-
free phone service and an answering machine.
AU-Pnuts plots consisted of one to 10 acres of
peanuts. Each plot was compared to the remainder
of the field treated by farmers using the
conventional fungicide program.
During the 1991 test season, spring rains
triggered early applications with AU-Pnuts. Initial
sprays were made on average at 33 days after
planting (DAP) in nonrotated fields and 36 DAP
in rotated fields, compared to an average of 42
DAP for the conventional program. Earlier
applications, when requested by AU-Pnuts, often
resulted in major differences in disease control.
Subsequent applications were coordinated with
infection periods. The average number of
fungicide applications with AU-Pnuts and
conventional programs was 5.6 and 6.0,
respectively.
1Ten producers started in the demonstration, but three
dropped out due to failure to follow AU-Pnuts advisories
and other technical problems.
[48]
On the farms in which AU-Pnuts was
successfully utilized, the combination of earliness
and timeliness resulted in significantly improved
season-long disease control. On average, AU-Pnut
plots had 10% less infection by end-of-season. No
failures of the AU-Pnuts system were reported,
and yields were higher (258 lb. per acre) in four of
five fields in which yields were compared.
The strength of the AU-Pnuts system may be
its ability to help in making wise decisions. Under
normal weather conditions, AU-Pnuts may often
save sprays due to timeliness. In heavy rainfall
years, AU-Pnuts may call for more sprays than a
conventional 14-day schedule. Based on research
results and suggestions from producers, AU-Pnuts
was revised for limited release in 1992 and 1993.
More information on use of AU-Pnuts in 1994 is
available through county Extension Service offices.
Davis and Mack, Department of Entomology;
Rodrfguez-KAbana, Backman, Brannen, and Jacobi,
Department of Plant Pathology.
Weather Variables Aid in Predicting
Abundance of Lesser Cornstalk Borer
T.P. Mack and D.P. Davis
THE LESSER cornstalk borer can severely
limit yields of peanuts when larvae feed on the
crown and developing pods and pegs of peanut
plants. Population outbreaks of this insect occur in
hot, dry weather in peanuts grown in sandy soils.
Research on the lesser cornstalk borer at the
Alabama Agricultural Experiment Station has
focused on the life history of this pest and how
weather influences population outbreaks. Since all
factors known to contribute to outbreaks involved
hot, dry weather, researchers began to explore the
possibility that certain variables could be
developed to predict outbreaks based on weather.
Such a prediction system would be extremely
useful to anticipate outbreaks of this insect,
because scouting for larvae is time-consuming and
growers often start scouting after damage occurs.
Many growers apply a preventative application of
a granular insecticide for control of larvae.
However, all the insecticides used for management
of the lesser cornstalk borer degrade in as few as
19 days in hot, dry weather. An insecticide
applied too early also will degrade, leaving plants
unprotected. If treatments are applied too late,
much of the damage to peanut plants already will
have occurred and yield will decline.
Through this research, a prediction equation
was developed by simplifying a complex
simulation model. This equation uses a single
variable incorporating positive effects of hot, dry
weather and the negative effects of normal, wetter
weather.
The equation developed is Y = (H-W). In this
equation, Y is equal to the LCB-days and
represents the cumulative effect of weather on
larval abundance. H is the number of days where
the temperature is 95*F or higher and less than 0.1
in. of rainfall occurs; W is the number of days that
the temperature is less than 95
0
F and 0.1 in. of
rainfall or more occurred. The variable H
represents days that produce a higher population.
Neutral days (i.e., more than or equal to 95
0
F and
more than or equal to 0.1-in. rainfall) do not
contribute to LCB-days. Thus, LCB-days are a
running total of the cumulative weather events
since planting. A cumulative total of zero to 10
LCB-days at 30 or more days after planting means
that scouting fields for the lesser cornstalk borer is
needed.
The usefulness of LCB-days was tested in four
validation experiments done at the Wiregrass
Substation, Headland, in 1989 and 1990. The tests
determined whether or not an application of a
granular insecticide for control of the lesser
cornstalk borer at a given number of LCB-days
increased yield. Conventionally tilled and planted
Sunrunner peanuts were used in both years. If
LCB-days were positive and a treatment was
suggested, a granular insecticide was applied and
yields were compared from treated and nontreated
plots. If LCB-days were negative, it was validated
that no yield increase would ensue if pesticide was
used, as compared with nontreated plots. The
granular insecticide used was chlorpyrifos
(Lorsban) applied at two lb. active ingredient per
acre in a band application over the row.
Plots were surveyed weekly for damage. Soil
was sieved weekly, or when dry enough to be
sieved during the growing season, to determine the
[49]
number of larvae present. Yields were taken from
the center two rows of each plot at crop maturity.
LCB-days were mostly negative in 1989 and
lesser cornstalk borers were rarely found.
Insecticide applied at negative values of LCB-days
did not increase yields, compared with yields in
the nontreated plots. In the outbreak year (1990),
LCB-days exceeded 35 and lesser cornstalk borers
were abundant. More than 20 larvae per yard were
found in some fields. Insecticide applied at 0.5, or
eight LCB-days increased yield compared with
yield in nontreated plots, and insecticide applied at
more than 20 LCB-days either did not increase
yield, or actually decreased yield.
These studies verify that LCB-days are useful
in timing scouting and applications of insecticide.
A three-tiered approach can be used with LCB-
days, as shown in the figure, which suggests
scouting at more than zero LCB-days, danger at
five to 10 LCB-days, and damage occurring at
more than 10 LCB days. Growers must record the
amount of daily rainfall and daily maximum
temperatures in each field throughout the growing
season and calculate LCB-days from planting.
Mack and Davis, Department of Entomology.
LCB days
20
10
Danger
0
-10 
No Scouting 
Needed
-20
20. 40 60 80 100 120
Days after planting
Three-tiered approach to timing scouting and applications of
insecticide for control of lesser cornstalk borer.
[50]
0
Estimating Abundance of Lesser
Cornstalk Borer Larvae One
Week in Advance
T.P. Mack and D.P. Davis
SAMPLING for lesser cornstalk borer larvae
is a time consuming and laborious process, since
the larvae live in the soil and are difficult to find.
Predicting population outbreaks before they occur
would be helpful, since pod and root-crown
damage is permanent. Can the abundance of
larvae be predicted from estimates of adult
abundance? The adult is a small moth that is
easily flushed from peanut fields, so predicting the
abundance of larvae from adults would be very
desirable.
The abundance of larvae and adults of the
lesser cornstalk borer was monitored in
conventionally tilled and planted Florunner peanuts
from 1984 to 1986 at the Wiregrass Substation,
Headland. Lesser cornstalk borer larvae were
sampled by sieving 10 three-ft. sections of a large
production field approximately weekly throughout
the growing season. The abundance of adults was
monitored by flushing male and female moths
from rows in the morning by beating plants with
a stick. Two people vigorously agitated plants
with a stick while another person identified and
counted moths that were flushed. Lesser cornstalk
borer adults were easily distinguished from other
small moths flushed from the rows by their unique
coloration and distinctive flight pattern.
The average number of larvae found by weekly
soil sieving was compared with the average
number of adults from flushing. Larval
abundance one week after the adult abundance was
used because eggs laid by the adults sampled by
flushing would hatch in about three days, with
small larvae present about four to seven days later.
The average number of larvae in any given
week increased linearly with an increase in adult
flush counts from the previous week indicating
that larval density could be predicted by adult
abundance. There was no year effect on this
relationship, so data were pooled over all three
years and a common slope was generated. The
equation is:
Y= -0.27 + 11.57X,
where Y = the average number of larvae per yard
in any given week from soil sieving and X = the
average number of adults per yard in the previous
week, as determined by flushing. The slope of
11.57 indicates that about 12 larvae per yard can
be expected to be found one week later for each
adult per yard flushed.
To validate this relationship, the abundance of
lesser cornstalk borer adults was determined in
five peanut fields in 1990 by flushing 30.3-m of
row in the morning, as described above. All fields
were conventionally tilled and planted with
Florunner peanuts. Fields were chosen based on
adult population size, so that a range of adult
populations could be tested. The abundance of
larvae was determined in the following week by
randomly taking three sieve samples in each field.
Means from four of the five model validation
fields in 1990 fell within the 95% confidence
limits for the regression equation, indicating that
the equation captures the pattern of the data and
that the equation agrees with the field data.
This equation could be a significant addition to
management of the lesser cornstalk borer, because
the use of adult flush counts allows for the
prediction of damaging larval populations before
they occur. The laborious, time-consuming and
destructive sampling for larvae can be reduced by
using this method. For example, if a grower
flushes no adults from fields for several
consecutive weeks, it is unlikely that an
economically damaging population of larvae is
present. However, if the number of adults per
yard increases for several consecutive weeks or if
a large number of adults is found on any given
week, then scouting for larvae should be
considered. Alabama Cooperative Extension
Service recommendations should then be consulted
to determine if control is needed.
Care should be taken in the applying this
equation to any and all situations. Fields that were
sampled in this study for larvae and adults were
conventionally tilled and planted runner peanuts.
Any factor that would change the relative
efficiency of soil sieving, such as reduced tillage
or twin rows, would affect this relationship.
Given these limitations, the regression equation
still should be a useful method of predicting
population outbreaks of the lesser cornstalk borer.
Mack and Davis, Department of Entomology.
[51]


ALABAMA AGRICULTURAL EXPERIMENT STATION
AUBURN UNIVERSITY
AUBURN UNIVERSITY, ALABAMA 36849-5403
Lowell T. Frobish, Director
NON-PROFIT ORG.
POSTAGE & FEES PAID
PERMIT NO. 9
AUBURN, AL