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FALL ARMYWORM: Evaluation
of Insecticides for Control
MAX H. BASS*
The fall armyworm Spodoptera
frugiperda (J.E.S.) has been noted as an
agricultural pest in Alabama since rec-
ords have been kept by the Auburn Uni-
versity Agricultural Experiment Station.
Although infestations occur every year,
only infrequently does this insect cause
extensive damage on a statewide basis.
During the summer of 1977, this insect
inflicted its most serious damage to date
on Alabama agriculture. It attacked
peanuts, soybeans, cotton, grain sor-
ghum, corn, sudan-sudex grasses,
Johnsongrass, Coastal bermuda, various
pasture grasses, and commercial hybrid
grasses on golf courses, 
lawns,
cemeteries, and football fields. Various
other crops were attacked to a lesser ex-
tent.
As the summer progressed, the fall ar-
myworm problem became increasingly
severe and standard chemicals recom-
mended for control failed to afford ex-
pected relief. The following tests were
conducted on an emergency basis to
evaluate certain labelled and unlabelled
insecticides for effectiveness against this
insect.
PROCEDURE
Six experiments were conducted on
control of fall armyworm. Three were
conducted on peanuts and three on grain
sorghum. Peanut test plots were 1/100
acre, replicated four times, and ran-
domized. Sprays were applied with a
CO2 pressurized sprayer delivering 10
gallons of mixed spray per acre. One bait
was used and it was distributed by hand
in a 12-inch band over the row. Grain
sorghum test plots were one acre, repli-
cated four times, and not randomized. All
materials were applied as sprays with a
Hahn Hi-Boy sprayer delivering 6 gal-
lons of mixed spray per acre.
Insecticides used in one or more of
these six tests were: monocrotophos
(Azodrin@), methomyl (Lannate? or
Nudrin@), Bolstar@, chlorpyrifos
(Lorsban?), methamidophos (Monitor?),
UC 51762, ethoprop (Mocap?), Am-
bush@, Pydrin@, Pounce@, FMC 45498,
parathion, methyl parathion, carbaryl
(Sevin@), Oftanol@, acephate (Or-
thene@), diazinon, trichlorfon (Dylox? or
Proxol@), methomyl bait (NuBait?), and
Savem@ (a finely ground carbaryl formu-
lation).
The efficacy of materials was deter-
mined by counting live fall armyworm
larvae 24, or 24 and 48 hours after the
application of insecticides. On peanuts
this was accomplished by randomly
selecting a 3-foot section of row, vigor-
ously shaking plants to cause the larvae
to fall to the ground, and counting the
live larvae that were dislodged. This was
repeated four times in each plot, thus
larval counts were made on 12 feet of row
in each plot. The same procedure was
followed in the tests on sorghum except
that differences in plant stand was ac-
counted for by counting the plants in
each 3-foot section and then calculating
the number of live larvae per plant at
each counting station.
*Professor, Department of Zoology-Entomology, Auburn University, Agricultural Experi-
ment Station.
RESULTS AND DISCUSSION
The economic injury threshold, based
on number of larvae per foot of row, has
not been established for the fall ar-
myworm. However, for purposes of de-
termining adequate effectiveness of ma-
terials, many researchers have used 80%
control as an acceptable level. For pur-
poses of this discussion, any material giv-
ing acceptable control had to reduce the
population by at least 80%.
In the first test on peanuts (table 1),
monocrotophos (Azodrin?), methomyl
(Lannate@ or Nudrin@), and Bolstar? all
afforded control of 80% or better at the
rates tested. Statistically these three ma-
terials were equivalent to each other in
effectiveness. Other materials which ap-
proached the 80% level of effectiveness
were chlorpyrifos (Lorsban?), metha-
midophos (Monitor?), and UC 51762.
Chlorpyrifos was used at 0.5 lb/acre 
ac-
tive ingredient (ai) in this test. In a later
test, this material was used at 0.75 lb/acre
(ai) and provided control well above the
80% level (tables 4 and 5). The synthetic
pyrethroids used in this test (Ambush?
and Pydrin?) failed to give adequate con-
trol of this insect at rates tested.
In test 2 (table 2), in counts made 24
hours after the insecticides were
applied, acephate (Orthene?) at 1 lb/acre
(ai), methomyl at 0.5 lb/acre (ai), 
and
methomyl bait (NuBait@) applied at 
the
rate of 20 lb of the 1.25% bait or 0.25
lb/acre (ai) provided control of 80% or
better. Acephate and methomyl 
were
statistically superior in effectiveness 
to
the bait at 24 hours, but at 48 hours (table
3) these three materials and diazinon 
[1
lb/acre(ai)] were all statistically 
equal
and all gave acceptable control.
Trichlorfon (Dylox? or Proxol?) 
and
carbaryl (Sevin?) were used and failed 
to
give acceptable control. Personal com-
munications with researchers in other
states have indicated that trichlorfon and
carbaryl generally have not been effec-
tive against this insect on peanuts. On
the other hand, observations by county
agents of farmer applications of both
trichlorfon and carbaryl have indicated
that under certain conditions both of
these materials have been effective [car-
baryl at 2 and trichlorfon at 1 lb/acre (ai)]
against fall armyworm when applied on
grasses. The diet of insects is known to
affect their susceptibility to certain in-
TABLE 1. AVERAGE NUMBER OF LIVE FALL ARMYWORM LARVAE PER 12 FEET OF Row PER PLOT
AND PERCENT CONTROL 24 HOURS AFTER TREATMENT 
WITH INDICATED INSECTICIDES.
PEANUTS, AUGUST 1977, TEST 1
No. live Percent
Material 
lb/acre (ai) larvae' control
Monocrotophos 5EC ........................ 
0.63 8.0 a 90
Methomyl 1.8EC ............................ 
0.45 13.3 a 84
Bolstar 6EC .... ...................... 
..... 0.75 14.0 ab 83
Chlorpyrifos 4EC ........................... 
0.50 20.3 b 76
Methamidophos 4EC ......................... 
1.00 20.5 b 76
UC 51762 75WP ............................ 
0.45 21.8 bc 74
Ethoprop 6EC .............................. 
1.00 27.5 cd 67
Ambush? 2EC ............................. 
0.10 35.5 de 58
Pydrin? 2.4EC ............................. 
0.10 37.0 ef 56
Ambush? 2EC .............................. 
0.05 40.3 ef 52
Parathion EC ............................... 1.00 
43.5 ef 48
Methyl Parathion EC ........................ 
1.00 45.0 efg 46
Carbaryl 80 W P .............................. 
1.50 46.5 fg 45
Oftanol? 6EC .............................. 1.00 
53.0g 37
Check 
83.8 h
'Mean of four replications. Means with the same 
assigned letter are not significantly different at
the 5% level.
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TABLE 2. AVERAGE NUMBER OF FALL ARMYWORM LARVAE PER 12 FEET OF Row PER PLOT AND
PERCENT CONTROL 24 HOURS AFTER TREATMENT WITH INDICATED INSECTICIDES.
PEANUTS, AUGUST 1977, TEST 2
No. live Percent
Material lb/acre (ai) larvae
1  
control
Acephate 75S ......... . .... 1.0 8.50 a 90
Methomyl 1.8EC ............................ 0.5 11.25 a 86
Methomyl Bait 1.25%
(on citrus pulp) ........................... 0.25 16.25 b 80
Diazinon 2EC ............................... 1.0 33.50 c 59
Trichlorfon 4EC ............................. 2.0 41.50 d 49
Carbaryl 80WP .............................. 2.0 53.50 e 35
Savem? 4EC ................................ 2.0 67.00 f 18
C heck ... o................................... 81.75 g
'Mean of four replications. Means with the same assigned letter are not significantly different at
the 5% level.
secticides and this could be a factor in
this case. The present research does not
elucidate this inconsistency.
Test 3 (tables 4 and 5) included only
materials which had shown promise in
previous tests. Counts of live larvae
made 24 hours after the insecticidal ap-
plication revealed that methomyl, chlor-
pyrifos, and monocrotophos gave accept-
able control at rates tested (table 4).
Forty-eight hours after application all
materials (methomyl, monocrotophos,
Bolstar?, methomyl bait, chlorpyrifos,
and acephate) were providing accept-
able control (table 5).
The results of tests 4, 5, and 6 are pre-
sented in table 6. These tests involved
only certain synthetic pyrethroids
(Pounce?, Pydrin? and FMC 45498) and
methomyl for control of fall armyworm
on grain sorghum. None of the synthetic
pyrethroids provided acceptable control
in any of these three tests. Ambush? and
Pydrin? had previously failed to afford
acceptable control in test 1 (table 1).
Methomyl was used as a standard treat-
ment in test 6 and provided 95% control
at the rate of 0.45 lb/acre (ai).
Based on the results of these six tests it
would appear that methomyl (Lannate?
or Nudrin?), monocrotophos (Azodrin?),
Fall armyworms on opposite page are shown on three crops: (top) peanuts; (mid-
dle) grasses; (bottom) corn. Note color variation. (Photos courtesy John C. French,
Cooperative Extension Service.)
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TABLE 3. AVERAGE NUMBER OF FALL ARMYWORM LARVAE PER 12 FEET OF Row PER PLOT AND
PERCENT CONTROL 48 HOURS AFTER TREATMENT WITH INDICATED INSECTICIDES.
PEANUTS, AUGUST 1977, TEST 2
No. live Percent
Material lb/acre (ai) larvae
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control
Methomyl 1.8EC ............................ 0.5 2.25 a 97
Acephate 75S ................................ 1.0 4.00 a 94
Methomyl Bait 1.25%
(on citrus pulp) ............................ 0.25 12.00 a 83
Diazinon 2EC ............................... 1.0 12.75 a 82
Trichlorfon 4EC ............................. 2.0 50.50 b 29
Carbaryl 80WP .............................. 2.0 58.00 bc 19
Savem? 4EC ........ ..................... ..... 2.0 64.50 cd 9
C heck....................................... 71.25 d
'Mean of four replications. Means with the same assigned letter are not significantly different at
the 5% level.
TABLE 4. AVERAGE NUMBER OF FALL ARMYWORM LARVAE PER 12 FEET OF ROW PER PLOT AND
PERCENT CONTROL 24 HOURS AFTER TREATMENT WITH INDICATED INSECTICIDES.
PEANUTS, SEPTEMBER 1977, TEST 3
No. live Percent
Material lb/acre (ai) larvae' control
Methomyl 1.8EC ............................ 0.50 2.50 a 95
Chlorpyrifos 4EC ............................ 0.75 5.25 a 89
Monocrotophos 5EC ......................... 0.75 7.50 ab 84
Bolstar@ 6EC ................... .......... 1.00 12.50 bc 73
Methomyl bait 1.25%
(on citrus pulp) ........................... 0.25 14.25 c 69
Acephate 75S ............................... 1.00 24.00 d 48
C heck....................................... 46.25 e
1Mean of four replications. Means with the same assigned letter are not significantly different at
the 5% level.
TABLE 5. AVERAGE NUMBER OF FALL ARMYWORM LARVAE PER 12 FEET OF Row PER PLOT AND
PERCENT CONTROL 48 HOURS AFTER TREATMENT WITH INDICATED INSECTICIDES.
PEANUTS, SEPTEMBER 1977, TEST 3
No. live Percent
Material lb/acre (ai) larvae' control
Methomyl 1.8EC ............................ . 0.50 1.75 a 96
Monocrotophos 5EC .......................... 0.75 3.25 ab 92
Bolstar? 6EC ................................ 1.00 3.75 ab 91
Methomyl bait 1.25%
(on citrus pulp) ............................ . 0.25 3.75 ab 91
Chlorpyrifos 4EC ............................ 0.75 4.75 ab 89
Acephate 75S ................................ 1.00 5.25 b 88
C heck....................................... 42.50 c
'Mean of four replications. Means with the same assigned letter are not significantly different at
the 5% level.
TABLE 6. AVERAGE NUMBER OF FALL ARMYWORM LARVAE PER SORGHUM PLANT AND PERCENT
CONTROL 24 HOURS AFTER APPLICATION OF INDICATED INSECTICIDES.
SORGHUM, JULY 1977
Material lb/acre (ai) No. live larvae/plant
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% control
TEST 4
Pounce@ ............................. 0.1 2.18 a 44
Pydrin@ ............................. 0.1 2.72 a 30
Check................................. 3.87 b
TEST 5
FMC 45498 .01 3.47 a 10
FMC 45498 ......................... .005 3.66 a 4
C heck ................................. 3.82 
a
TEST 6
Methomyl ........................... .45 0.2 b 95
FMC 45498 .......................... .01 2.8 a 35
FMC 45498 ........................... .005 3.7 a 16
C heck ................................ 4.3 a
'Four 3-foot sections of row were chosen per plot. Larvae were shaken onto a ground cloth. The
number of larvae were divided by the number of plants to obtain larvae/plant. Numbers shown
are the means of four replications. Means with the same assigned letter within each test are not
significantly different at the 5% level.
chlorpyrifos (Lorsban@), methomyl bait
(Nubait?), Bolstar?, and acephate (Or-
thene?), at rates indicated in the various
tables will provide acceptable control of
the fall armyworm. However, these re-
sults are based on only 1 year's research.
Also, some of the materials used are not
labelled for use on some crops attacked
by the fall armyworm. Therefore, presen-
tation of these data does not constitute
recommendations for use.
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