RESEARCH UPDATE
'1991
NUT
Rotations for
Improved Peanut
Production
Results following 3 years of rota-
tion with peanuts clearly illustrate
the benefits of corn and bahiagrass in
improving peanut yields. While
nonrotated peanuts yielded 2,700
pounds per acre, rotation with, 1
year of corn or bahiagrass pushed
yields to 3,200 and with 2 years of
bahia improved yields to 3,700
pounds per acre.
These yield increases were not
the result of white mold control.
Results indicate that 1- and 2-year
rotations did not reduce severity of
this disease.
One and 2-year rotations did re-
duce damage from nematodes and
leafspot, making the peanuts more
rank and apparently more suscep-
tible to white mold damage. The
addition of Folicur fungicide (two
applications during the season)
reduced white mold by 75-80 per-
cent, reduced limb rot, and increased
yields from 600 to 1,200 pounds per
acre.
P.A. Backman, J. Jacobi, D. Davis, and
R. Rodriguez-Kabana
New Herbicide Systems Doing the Job on Weeds
For many years peanut growers
used the so called "Cadillac Treat-
ment," the primary components be-
ing dinoseb and alachlor, to control
weeds. The loss of dinoseb-contain-
ing herbicides in 1986 eliminated one
component of the system, and the
loss of alachlor (Lasso?) may occur
in the future.
Fortunately, several new products,
such as Gramoxone?, Classic?,
and Basagran@ appear at this time
to be adequate replacements. And,
a new herbicide, Pursuit?, if it ac-
quires expected Federal registration
this year, will provide even greater
flexibility in weed control in the
Southeast.
For the past few years, AAES re-
searchers have evaluated tank mixes
containing Gramoxone for weed
control in peanuts. The most suc-
cessful additives for Gramoxone are
2,4-DB and Basagran. Both of these
herbicides tend to improve weed
control relative to either material
applied alone.
Basagran tends to inhibit the
penetration of Gramoxone into
the foliage of the treated plants,
resulting in less injury to the
peanut plant; hence Basagran is
perceived as a "safener" for
Gramoxone. However, this antago-
nism also occurs with some weeds,
and, depending upon the species of
weed in question, control can be re-
duced. Likewise, some species, such
as prickly sida and 
morningglory,
are more sensitive to Basagran than
to Gramoxone, and with these
continued on page 2
Effect of Gypsum on Peanut Yield
Calcium is the plant nutrient most
often associated with limiting pea-
nut production. In nine on-farm
experiments, conducted in 1987 and
1988, gypsum provided several
positive effects on yield and quality
of Florunner, GK 7, Sunrunner, and
Southern Runner peanut varieties.
Peanut yields for all varieties were
significantly increased with gypsum
addition at two locations (3 and 4) in
1987 and one location (3) in 1988, table
1. This was expected since the soil
continued on page 2
WA! i[i [ UBIURN UNIERSITY
LOWEL T ftosii DIRCTO Au~RN NIVESIT, ALBAM
Effect of Gypsum, continued Ta
Ca ranged between 196 and 214
pounds per acre for the variety
check plots at these sites, table 2.
Previous research defined the
soil test Ca level needed for
maximum yield of Florunner to
be 250 pounds per acre. There-
fore, increased yields were ex-
pected for Florunner, if soil test
Ca was below this level, as was
the case for sites 3 and 4 for 1987
and site 3 in 1988. Since all the
varieties tested were runner
type peanuts, they were ex-
pected to respond similarly. There
was only one instance in which
yield was increased by gypsum
when the check plot soil test Ca
level was above 250 pounds per
acre (GK-7 had an increase of 438
pounds per acre at site 5 in 1987).
It should be noted that GK-7
failed to show a yield increase when
soil Ca was 384 pounds per acre at
another location (site 2, 1988).
Relative yields of the check plots
were determined by dividing the
check plot yield by the treatment
yield. Then yields were regressed
against soil test Ca values to deter-
mine if the varieties tested required
different soil Ca levels to produce
maximum yield. Regression analyses
determined that maximum yield for
Florunner was reached at 250
pounds per acre of soil Ca, which
is identical to the critical value
found in previous AAES research.
New Herbicides, continued
weeds the tank mix has been more
effective in AAES tests.
It appears that growers will reduce
their reliance on Lasso in the coming
growing season. Lasso has been
widely used for its control of Florida
beggarweed, however AAES re-
search has shown that satisfactory
control of this weed can be achieved
through early season applications of
Gramoxone, and/or later season ap-
plications of the recently registered
herbicide Classic.
G.R. Wehtje
ble 1. Effect of 500 Pounds Per Acre of Gypsum Topdressed at Early Bloom on Yield Per Acre for Four
Peanut Varieties at Nine Locations, 1987 and 1988
Site/year 
Florunner 
Sunrunner 
GK-7 Southern 
R
No gyp Gyp No gyp Gyp No gyp Gyp No gyp Gyp
Lb. Lb. Lb. Lb. Lb. Lb. Lb. Lb.
1987
............................. 1,820 2,020 2,010 1,680 1,820 1,590 2.240 2,150
2 ............................. 3,290 3,070 3,290 2,820 3,050 3,080 3,020 2,900
3 ............................. 2,640 3,570 540 2,040 310 2,380 1,150 3,000
4 ............................. 2,190 3,130 2,100 2,890 1,760 2,970 1,120 2,760
5 ............................. 3,190 3,290 2,860 3,810 2,860 3,330
1988
1 ............................. 2,650 2,660 3,270 3,060 2,510 2,370 2,840 2,840
2 ............................. 3,450 3,380 3,240 2,860 3,130 2,960 3,480 3,340
3 ............................. 3,110 3,580 4,040 4,380 3,290 3,760 3,270 4,210
4 ............................. 3,180 3,420 3,620 3,880 3,550 3,450 3,110 3,240
~1
All other varieties tested re- Table
quired a somewhat higher
soil Ca level than Florunner
to produce maximum yield.
Maximum yields for 1987
Sunrunner, GK-7, and 1 ......
Southern Runner were ob- 
2 ......
3 ......
tained at 286, 366, and 286 4
pounds per acre of soil Ca, 5 ......
respectively. These values 1988
may be subject to error since 2.
there were few Ca deficient 3 ......
sites. 
4 ......
There were differences in
yield among the varieties on the
treated plots, but no variety consis-
tently yielded the most or the least
across the field experiments. For
example, at site 1 in 1987, Southern
Runner had the highest yield, but at
site 4 in 1988 it had the lowest yield.
Thus, no variety consistently out-
performed the other varieties.
Percentage of sound mature ker-
nels (SMK) was generally increased
by gypsum addition at the same sites
as yield. Only Florunner and GK-7
at site 3 in 1988 failed to show an
increase in SMK concomitant with a
yield increase. The GK-7 variety
showed an increase in SMK on four
"high Ca" sites, indicating the possi-
bility of a higher calcium require-
ment for GK-7 to achieve maximum
SMK than for the other varieties.
J.F. Adams and D.L Hartzog
Tomato Spotted Wilt Virus Stable in Alabama Peanuts
Tomato spotted wilt virus (TSWV),
which was first found in Alabama's
peanut crop in 1986, has caused seri-
ous crop loss in other peanut-produc-
ing states. Most recently, peanuts in
Georgia and Mississippi were
heavily damaged by TSWV. So far,
Alabama Experiment Station field
surveys indicate that this disease has
had little impact on peanut produc-
tion in Alabama.
In each peanut-producing county,
one field for each 5,000 acres of pea-
nuts, with a three field minimum for
each county, was checked each year.
A total of 80 to 85 fields was sur-
veyed annually from 1987 to 1990. In
continued on page 3
2. Fall Soil-test Values Per Acre for Check Plots
From the Nine On-Farm Experiments
ear pH Ca P K Mg
Lb. Lb. Lb. Lb. Lb.
........ 6.1 402 91 71 93
.......... 6.2 429 30 136 148
.......... 5.2 196 60 89 15
.......... 5.5 214 22 52 30
.......... 6.0 38 80 60 78
.......... 6.4 616 20 82 143
.......... 6.0 384 53 111 102
.......... 5.4 196 12 20 16
....... 6.2 473 24 92 104
Seed Size Not Correlated to Herbicide Damage
It has been widely accepted
that small seed produce
smaller plants, and these plants
are inherently more easily in-
jured by herbicides. Tests were
established to examine this idea
using small, medium, and large
seed. Herbicide treatments
ranged from none to systems
considered to be fairly injuri-
ous to peanuts, such as para-
quat applied twice within a
short time period. This test
was conducted at the Wire-
grass Substation, Headland,
and at Jay, Florida.
A summary of the data shown
in the table reveals that progres-
sively larger seed results in a
stepwise increase in yield, how-
ever the overall difference is not
great. None of the treatments
Tomato Spotted Wilt Virus, continued
each field, 
plants with 
Incide
typical TSWV symptoms
were counted in five ran-
domly selectedareas. Each Ye
area was two adjacent
rows 100 feet in length for
a total of 1,000 
row feet 
1986
per field. Stand density 1987
in each field 
also was esti- 
1988
1989
mated in order 
to calculate 
1990
the percentage of TSWV-
infected plants.
TSWV is well established
throughout Alabama's peanut
belt. With the exception of 1987,
when virus-infected peanuts
were seen in only 41 percent of
fields, TSWV has been found in
approximately 90 percent of
fields surveyed. As noted in the
table, highest levels of this dis-
ease were seen in 1986, while the
incidence of TSWV-infected pea-
nuts was lowest in 1987. Over the
past 3 years, mean disease inci-
dence across Alabama has held
were particular-
ly injurious to
the crop; how-
ever, as expect-
ed, paraquat ap-
plied twice re-
sulted in the least
yield.
There was no
treatment by
seed size interac-
tion, meaningthat
Peanut Yield as influenced by Seed Size and Herbicides, Average Over
All Locations and Years
Yield per acre by seed size
Herbicide, lb./acre
Small Medium Large Mean
Lb. Lb- Lb. Lb.
Paraquat, 0.13 ............................ 4,010 4,020 4,260 4,100
Paraquat, 0.25 ............................ 3,850 3,880 4,010 3,910
Paraquat-twice, 0.13 .................. 3,510 3,930 3,710 3,720
Paraquat + alachlor, 0.13 + 3........ 3,870 4,380 4,310 4,190
Paraquat + alachlor, 0.26 + 3........ 3,790 4,090 4,190 4,030
Untreated ..................................... 3,830 4,220 4,180 4,070
Mean .................. ................... 3,810 4,080 4,110
none of the seed sizes were any
better able to handle the herbi-
cide-induced stress.
Conversely, none of the seed sizes
were uniquely disadvantaged
when it came to tolerating excessive
levels of herbicides. Large seed sim-
ply produce larger plants, so the
net affect is similar to having an
earlier planting date.
G.R. Wehtje
nce of Tomato Spotted Wilt Virus in 80-85 Surveyed
Fields, 1987-90
Incidence of
ar Fields 
with 
diseased plants
diseased plantsp
Range Mean
Pct. Pct. Pct.
............... 94 0-3.1 0.49
............... 41 0 -0.3 0.02
............... 90 0 -1.6 0.19
............... 92 0 -2.3 0.21
............... 87 0 -1.4 0.20
steady at 0.2 percent. In any single
field over the 5-year 
survey period,
only 3.1 percent of plants examined
showed typical TSWV symptoms.
Recently in most fields, the inci-
dence of diseased plants was less
than 0.5 percent. Late summer
droughts, which severely damaged
dryland peanuts in several 
counties,
probably interfered with identifi-
cation of virus-infected plants.
A.K. Hagan, J.R. Weeks,
J.C.French, and R.T. Gudauskas
LCB Damage Higher In
Late Planted Peanuts
In a 2-year test at the Wiregrass
Substation, Headland, lesser corn-
stalk borer abundance was greater in
peanuts planted in May than in June.
However, tillage system and burning
stubble had little effect on abun-
dance of this insect.
Two planting dates (mid-May and
early June) and three tillage systems
(conventional, reduced, and burned
stubble) were used in the test. The
reduced tillage treatment was in-
cluded because it usually decreases
soil temperatures, so it should slow
the development of the lesser corn-
stalk borer.
Wheat stubble wasburned in some
plots because the foreign literature
indicates that lesser cornstalk borer
adults are attracted to 
burned stubble,
and because burning stubble prior to
planting is a common practice in the
Wiregrass region of Alabama. The
abundance of lesser cornstalk borers
was monitored weekly with pitfall
traps.
Lesser cornstalk borer abundance
varied with year, with more insects
occurring in 1986 than in 1987. About
1.9-fold more lesser cornstalk borers
were captured in traps in late-planted
continued on page 4
TSWV Vectors Fluctuate
During Growing Se ason
Tobacco thrips and western flower
thrips, two of five species known to
vector tomato spotted wilt virus
(TSWV) in peanuts, have commonly
occurred in field samples taken in
Alabama since 1987. Tobacco thrips
consistently was the most abundant
species found (see table). Western
flower thrips was not known to in-
fest Alabama fields prior to 1987.
Since tobacco and western flower
thrips have been the most abundant
species found in weekly samples,
the potential exists for significant
spread of TSWV. However, results
indicate thrips populations peak 2-4
weeks after peanut emergence and
decline sharply after 6 weeks. Based
on early TSWV infection, 1 percent or
less of thrips migrating into peanut
fields caused the initial infection
levels found in peanuts in early June.
AAES tests were conducted at the
Wiregrass Substation, 
Headland,
and at three grower sites. Five
samples were taken from each plot
and five peanut terminals were taken
LCB Damage, continued
peanuts in both years. Tillage system
did not affect the abundance of lesser
cornstalk borers in either year, so
burning stubble did not increase the
number of lesser cornstalk borers in
this test. Planting peanuts in May and
not in June should effectively decrease
lesser cornstalk borer abundance in
conventionally tilled and reduced
tillage peanuts.
T.P. Mack and C.B. Backman
EDITOR'S NOTE
Mention of company or trade names does not indicate
endorsement by the Alabama Agricultural Experiment
Station or Auburn University of one brand over another.
Any mention of non-label uses or applications in excess
of labeled rates of pesticides or other chemicals does not
constitute a recommendation. Such use in research is
simply part of the scientific investigation necessary to
fully evaluate materials and treatments.
Information contained herein is available to all persons
without regard to race, color, sex, or national origin.
March 1991 4M
from each 
sample. These 
Thrips SF
terminals were washed
in an alcohol solution and
thrips were filtered out 
Date
and counted.
Thrips damage to pea-
nuts is characterized by 5/15 .......
feeding in the unfolded 5/23 .....
5/30 .......
new leaves. 
This causes 
6/6........
scarred, deformed leaves, 6/13 .......
resulting in stunted pea- 6/20......
nut leaves. 6/27.......
7/6 ........
Insecticide treatments 
7/12 .......
also are being evaluated 
7/19 .......
for control 
of thrips 
and 7/26 
.......
subsequent effect on
TSWV. Tests were conducted in 1988
and 1990 to evaluate the efficacy of
in-furrow applied insecticides and
foliar sprays to control thrips. Al-
though most treatments reduced
thrips populations, this reduction
had no significant effect on the
level of TSWV found in those
pecies Found in Peanut Field Surveys, Wiregrass
Substation and Growers Fields
Total Western
thrips/5 Tobacco flower
blooms 
thrips 
thrips non-vectors
No. Pct. Pct. Pct.
...... 7.0 69 28 3
...... 3.6 86 13 1
...... 5.0 80 18 2
...... 34.0 69 25 6
...... 9.0 62 27 11
7.7 65 14 21
...... 14.5 64 6 30
...... 10.7 50 9 41
...... 15.3 71 7 22
...... 30.0 88 4 8
...... 21.0 93 3 4
plots. Since TSWV infection levels
have remained below 5 percent each
year since 1986 in Alabama 
peanuts,
there appears to be no economic ben-
efit to using supplemental applica-
tions of insecticides to reduce thrips
populations.
J.R. Weeks
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