B-1048

February
1966

 
  
 

Comparative Effectiveness of Certain Insecticides

for Killing BollWorms and Tobacco BudWorms

Perry L. Adkisson and S. J. Nemec
Respectir/ely, professor and research assistant, Department of Entomology

 
  
  
 
 
  
 
  
 
  
 
   
  
  
 
 
  
   
 
 
 
  
  
 
  
 
  
  
  
  
 
 
  
 

Summary

 e first significant evidence of the development
'tance by the bollworm, Heliotbis zen Boddie, to
“des other than DDT was determined in 1965.
‘bollworm was found to possess resistance to
A Sevin, strobane-DDT and toxaphene-DDT. The
~ budworm, Heliothis oirescens (F.), previously
 known to be resistant to these insecticides.
j er, an even greater level of resistance was de-
l d by the tobacco budworm to these toxicants
p; the 1965 growing season. Laboratory evalua-
 were made to determine the efficiency of a great
 r of insecticides and insecticidal mixtures for
g resistant bollworms and tobacco budworms. Re-
 indicated that mixtures of methyl parathion or
rin with endrin, Sevin, strobane, toxaphene or
inc-DDT and toxaphene-DDT showed great pro-
,‘ for controlling the two species. Methyl parathion
5 zodrin alone also were highly effective in killing
 and tobacco budworm larvae when used in
‘iopriate quantities.

Introduction

- The continued development of insecticide resist-
p, by the bollworm and the tobacco budworm is
i one of the most serious problems faced by Texas
a. producers. These two pests continued to de-
" p resistance to many of the most commonly used
ljicides during the 1965 growing season. Most
 cers, however, prevented damaging losses from
i ing by using certain of these toxicants. This
red not because the bollworm and tobacco bud-
v-m had become lessh resistant to the insecticides, but
use the populations “generally were small. Under
n conditions, it is necessary to kill only a relatively
A percentage of the population to prevent crop
When the bollworm and tobacco budworm popu-

 

lations again attain great numbers and persist in cot-
ton for periods of several weeks, control may be
extremely difficult to obtain with most of the chlorin-
ated hydrocarbon and carbamate type insecticides.

The tobacco budworm was first reported to have
developed resistance to DDT in Texas in 1961 and the
bollworm in 1962 (Brazzel, 1962, 1963a). Since this
time, the tobacco budworm has developed varying levels
of resistance to endrin, Sevin, strobane-DDT and toxa-
phene-DDT (Adkisson, 1964; Adkisson and Nemec,
1965). Until the present there has been only slight
evidence that Texas bollworms were developing resist-
ance to any of the commonly used cotton insecticides
other than DDT (Adkisson and Nemec, 1965). The
present study shows that this situation no longer is true.

Methods and Materials

Bollworm and tobacco budworm moths were col-
lected almost daily during the growing season from
light traps stationed in cotton fields near College Sta-
tion. Larval progeny of these adults were reared on
the wheat germ diet of Adkisson et al. (1960). The
diet was fortified with Vanderzant’s Insect Vitamin
Fortification as supplied by Nutritional Biochemicals
Corporation, Cleveland, Ohio. The larvae were reared
in continuous illumination at 80¢ 5° F. Only third
and fourth instar larvae which weighted between 25
and 6O mg. were tested.

The first method of testing involved direct applica-
tion of microgram quantities of each insecticide to the
dorsal thoracic surface of each larva. Serial dilutions
of selected insecticides in acetone solution were pre-
pared and applied in scalar doses to individual larva
in 111.1 droplets. Immediately after treatment, each
larva was returned to the rearing vial. Mortality rec-
ords were made 48 hours after application of insecticides.
Untreated control groups were maintained for each treat-
ment series. This was done so that treatment mortalities
could be adjusted by Abbott's (1925) formula to cor-
rect for any natural mortality occurring in the test
population. Doses were replicated at least four times,

i‘ TEXAS A&M UNIVERSITY
‘ TEXAS AGRICULTURAL EXPERIMENT STATION O

R. E. Patterson, Director, College Station, Texas

with each replicate generally including 25 or more
larvae. LD50 values were computed from certain of the
collected data by the Data Processing Center, Texas
A&M University.

The second method of testing involved the use of
potted cotton plants. Individual plants were sprayed
with a hollow-cone nozzle calibrated to deliver the
equivalent of 3.5 gallons of water-emulsion spray mix-
ture per acre. The plants were allowed to dry for
1 to 2 hours in the open air before being transported to
a continuously light room maintained at 80: 5° F.
Fourth instar larvae weighing between 40 and 6O mg.
were placed on the leaf surfaces and held singly in
small snap-on type plastic screen cages of about 11/2
inches in diameter. Treatments were replicated three
times with each replicate including 20 larvae. Mortality
records made 48 hours after treatment were adjusted
according to Abbott’s (1925) formula to correct for
natural mortalities occurring in untreated control groups.

Results and Discussion

Results, summarized in Table 1, show the percent-
ages of bollworm larvae killed with each concentra-
tion of insecticide for the years 1962 through 1965.
Percentages of larvae killed with any given concentra-
tion of each insecticide generally were smaller in 1965
than in previous years. This means that greater dosages
of each insecticide were required in 1965 to produce
comparable mortalities than in previous years.

Similar results for the tobacco budworm are pre-
sented in Table 2. These data show that the tobacco
budworm also gained in resistance to the selected in-
secticies. Generally, greater dosages of each insecti-
cide were required in 1965 than in previous years to
obtain comparable percentages of larvae killed.

TABLE 1. COMPARATIVE MORTALITIES OF THIRD AND FOURTH INSTAR BOLLWORM LARVAE PRODUCED BY CERTAIN INSECTICIDES 48 p
AFTER TOPICAL APPLICATION. LARVAE WERE PROGENY OF ADULTS COLLECTED IN LIGHT TRAPS NEAR COLLEGE STATION 1'

‘more resistant to endrin, 181.6-fold more resist

  
 
  
   
   
  
   
  
  
  
   
    
 
  
   
  
  
  

>-

The LD50 value is the calculated amount of '
cide required to kill 50 percent of a treated pop "
This statistic provides the best means for meas 5'
increase in resistance by an insect population .
specific toxicant. LD50 values calculated from if
presented in Tables 1 and 2 are given in Table 3;
values are expressed on the ‘basis of microgr 
insecticide per gram of larva. "l. 1

These results show that the bollworm has cle ;
a high level of resistance to most of the ins,
tested. An estimate of the magnitude of 
resistance by the population may be gained by M:
the 1965 LD50 value by the LDM, values of l
This type calculation indicates that the bollwo
1965 was 33,333-fold more resistant to DDT, 
more resistant to endrin, 4.5-fold more resis 
Sevin, 20.8-fold more resistant to strobane-DD_
11.5-fold more resistant to toxaphene-DDT 
1960. This increased resistance has mostly n:
since 1964 (Adkisson and Nemec, 1965) and A 
be shown later in the present report the percent
larvae killed in the 1965 tests with the above rn i,
were smaller than in 1964. ;

LD50 values for the tobacco budworm for
and 1965 also are reported in Table 3. These sho
the tobacco budworm population also is highly 
to the insecticides tested. The tobacco budworm w;
1965 was 127-fold more resistant to DDT, 215.

Sevin, 15.2-fold more resistant to strobane-DDf
7.5~fold more resistant to toxahpene-DDT t,“
1961. Needless to say, field control of large -"
tions of the tobacco budworm with these inse I
is practically impossible. ___

The decreased effectiveness of these ins L

Dosage, [L95 per larva

Compound Year‘ 0.625 1.25 2.5 5.0 10.0 20.0 40.0 80.0 160.0
Percentage mortalities
DDT 1962 42.2 50.6 50.6 49.4
1963 30.6 48.1 43.9 48.1 57.1
1964 10.1 27.3 35.4
19,65 12.4 8.3 17.5
Endrin 1962 47.9 75.5 96.9 93.8 100.0
1963 8.4 29.5 60.0 78.9 82.3 92.6
1964 32.6 54.3 83.7
1965 27.1 51.0 59.4 76.0
Sevin 1962 37.8 46.6 70.0 81.1
1963 28.4 45.3 44.2 57.9 71.6
1964 20.4 69.4 63.3 84.7 89.8 92.9 94.9 100.0
1965 35.9 26.8 27.2 40.6 57.5 58.9 57.4 66.1
SIrobane-DDT 1962 35.6 55.2 77.0
1963 3.2 27.7 56.4 61.7 85.1 94.7
1964 12.5 39.3 49.5 83.8
1965 28.7 54.3 74.5 75.5
Toxaphene-DDT 1962 23.2 52.5 68.6 78.7 94.9
1963 29.0 54.8 63.4 83.9 82.8
1964 30.6 43.9 58.2 72.4 87.8 90.8 100.0
1965

‘Dala for 1962 from a report by Brazzel (19631)).
2

38.8 55.1 62.2 78.6 86.7

   
 

AFTER TOPICAL APPLICATION.

‘IMPARATIVE MORTALITIES OF THIRD AND FOURTH INSTAR TOBACCO BUDWORM LARVAE PRODUCED BY CERTAIN INSECTICIDES
LARVAE WERE PROGENY OF INSECTS COLLECTED IN THE FIELD AND IN LIGHT TRAPS NEAR
COLLEGE STATION

Dosage, pg: per larva

Year‘ 0.625 1.25 2.5 5.0 10.0 20.0 40.0 80.0 160.0 320.0
Percentage mortalities

1962 0.0 32.2 12.9 23.6 33.3
1963 0.0 0.0 19.8 34.1 44.1
1964 15.1 18.3 16.1 33.3 29.0
1962 32.9 56.7 71.1

1963 17.5 42.3 51.5 50.5 61.9

1964 27.1 33.3 49.0 42.7 34.4 47.9 29.2

1965 37.9 27.1 35.7 49.6
1962 36.1 35.1 51.5

1963 13.2 34.1 42.9 39.6 46.2 33.1

1964 7.3 24.0 42.7 32.3 - 34.4 26.0

1965 23.0 20.0 ' 28.0 37.0
1962 1 1.3 24.7 47.4 49.5 75.3

1963 23.2 40.0 52.6 63.2

1964 36.1 44.5 50.0 69.4

1965 23.0 29.0 34.0 51.0
I962 6.2 32.0 48.5 53.6

1963 10.8 50.5 45.2 57.1

1964 7.1 17.5 35.1 32.9 49.1 55.1

1965 28.0 44.0 61.0 69.0

962 from a report by Brazzel (1963b).

  
   
   
    
   
   
  

'~ DEVELOPMENT o|= RESISTANCE BY m: BOLLWORM AND
jauowonm, AS axrnsssso BY INCREASED to... VALUES,
 to 196s TO CERTAIN cutonmmso HYDROCARBON
' AND CARBAMATE INSECTICIDES

LDw, Mg/G of larva

Bollworm Tobacco budworm
1960“ 1965 1961“ 1965
0.03 1000+ 0.13 16.51 A
,  0.01 0.13 0.06 12.94
’»_ 0.12 0.54 0.30 54.47
I T 0.05 1.04 0.73 11.12
0.04 0.46 0.47 3.52

“ our

 s for 1960 and 1961 were obtained from reports by
' al. (1961) and Brazzel l1963a).

 to 1965 for controlling the bollworm and
 budworm is shown by the data presented in
 The materials were sprayed on potted plants
equivalent to field dosages. The percentages
 of each species killed by equivalent doses of
cticide were smaller in 1965 than in 1964.
_= irms the results obtained by the topical applica-
i-t summarized in Tables 1, 2 and 3.

DECREASE IN EFFECTIVENESS OF CERTAIN INSECTICIDES
NTROLLING BOLLWORMS AND TOBACCO BUDWORMS
a BETWEEN 1964 AND 1965

Actual toxicant, Percent kill, 48 hours

 (s) pounds per acre 1964 196s
Bollworm
0.251. 90 52
1.6 93 76
2.0-1.0 90 47
2.0-1.0 90 52
Tobacco budworm
0.4 40
1.6 48 31
2.0-1.0 55 19
2.0-1.0 45 21

Results obtained in the preceeding study showed
that certain of the insecticides recommended in Texas
for bollworm and tobacco budworm control are becom-
ing ineffective against resistant strains of the two species.
For this reason a number of insecticides and insecticidal
mixtures were tested for effectiveness against the resis-
tant insects. These tests were conducted to find ma-

terials which may have promise for field use.

The

insecticides were applied as water emulsions and sprayed
at rates equivalent to field dosages.

Results, sumarized in Table 5, list the insecticides
in decreasing order of effectiveness which killed more

TABLE 5.

INSECTICIDES THAT KILLED MORE THAN 80 PERCENT OF

THE FOURTH INSTAR BOLLWORM LARVAE CAGED ON POTTED PLANTS
TREATED WITH 3.5 GALLONS OF TOTAL SPRAY PER ACRE, 1965

Actual toxicant

percent mortality,

lnsecticidels) pounds per acre 48 hours
Endrin-Matacil 0.25-0.5 100
Methyl parathion 1.0 100
Toxaphene-m.parathion 4.4-0.31 100
Toxaphene-m.parathion 3.9-1.25 100
Toxaphene-m.parathion 2 0-0.25 100
Azodrin-toxaphene 0.25-1.0 100
Toxaphene-mparathion 1 94-0.63 98
Strobane-mparathion 2 0-0.25 98
Toxaphene-mparathion 4 4-0.63 98
Azodrin-Endrin 0 6-0.25 97
Strobane-DDT-mparathion 3 0-0.75-0 25 97
Azodrin-Strobane 0.25-1.0 97
Toxaphene-DDT-m.parathion 3‘.0-0.75-0 25 95
Azodrin 0.8 92
Azodrin-Sevin 0.6-0.8 91
Endrin 0.4 89
Endrin-m.parathion 0.4-0.25 88
Strobane-DDT-mparathion 2.0-1.0-0.25 88
Methyl parathion 0.50 87
Strobane-Sevin 2.4-0.8 87
Toxaphene-EPN 2.0-0.25 84
Sevin 2.4 82
Azoclrin 0.6 81
Guthion-Strobane 0.5-0.3 81

than 80 percent of the test larvae. Insecticides which
killed less than 8O percent of the bollworm larvae at
rates tested are given in Table 6. The combined data
show that methyl parathion or Azodrin must be added
to endrin, Sevin, strobane, toxaphene, strobane-DDT,
or toxaphene-DDT if great percentages of the larvae
are to be killed. However, Azodrin or methyl para-
thion alone killed approximately 90 percent of the
treated larvae when applied at rates equivalent to 0.8
and 0.5 pound, respectively, of actual toxicant per acre.
A possible potentiation of the chlorinated-hydrocar-
bons by Azodrin was indicated by the increased effective-
ness of the toxaphene-Azodrin and strobane-Azodrin
mixtures over that obtained by the use of the chlorinated-
hydrocarbons alone.

Results of similar tests with the tobacco budworm
are given in Table 7. None of the insecticides at
the rates tested was as effective against the tobacco
budworm as against the bollworm. Poor control was
produced with the chlorinated hydrocarbons and Sevin.
The percentages of tobacco budworm larvae killed in
tests with mixtures of methyl parathion or Azodrin
with the chlorinated hydrocarbons or Sevin were much
greater than where the latter materials were used alone.

These data clearly confirm the evidence summarized
in Table 3 which showed that the bollworm and tobacco
budworm have developed resistance to the insecticides
previously recommended for their control in Texas. A
comparison of results obtained in 1965 with those of
1964 show that there has been a considerable increase
in resistance during the past year especially in bollworm
populations. The bollworm and tobacco budworm are
becoming increasingly more difficult to kill with eco-
nomical dosages of the chlorinated hydrocarbon or car-

TABLE 6. INSECTICIDES THAT KILLED LESS THAN 8O PERCENT OF THE
FOURTH INSTAR BOLLWORM LARVAE CAGED ON POTTED PLANTS
TREATED WITH 3.5 GALLONS OF TOTAL SPRAY PER ACRE, 1965

Actual toxicant, percent mortality,

Insecticide(s) pounds per acre 48 hours
Toxaphene-DDT-m.parathion 2.0-1 .0-0.25 78
Sevin 1.6 76
Sevin 0.8 76
Strobane-EPN 2.0-0.25 73
Toxaphene 6.0 73
Endrin-m.parathion' 0.25-0.25 71
Sevin-Thiodan 0.8-0.5 ' 71
Ethyl parathion 0.5 70
Malathion 2 0 65
Toxaphene-TDE 2 O-1.0 64
Chlordane-DDT-mparathion 1.0-1.0-0.25 64
Thiodan 1.0 58
EPN 0.5 57
Methyl parathion 0.25 55
Sevin-mparathion 0.8-0.25 53
Endrin 0.25 52
Toxaphene-DDT 2.0-1 .0 52
Strobane-DDT 2.0-1.0 47
Malathion-TDE 1.0-1.0 32
Chlordane-DDT 1.5-1.5 26
BHC-DDT 0.9-1.5 24
TDE 1.0 12
DDT 1.0 7
4

obtained. The data suggest that the chlorinated i

  
   
   
  
   
   
   
 
   
  
     
   
 
   

TABLE 1. EFFECTIVENESS OF CERTAIN INSECTICIDES A;
FOURTH msmn TOBACCO aunwom LARVAE CAGED ON -~
PLANTS TREATED WITH 3.5 GALLONS or tom. SPRAY PER y

196s a

percent m f

Actual toxicant, p

InsEcticideIs) pounds per acre 48 h '1
Sevin-m.parathion 1.6-0.25
Matacil-m.parathion 0.5-0:"25
Strobane-DDT-mparathion 2.0-l 5.0-0.5
Toxaphene-DDT-m.parathion 2.0-1.0-0.5
Strobane-mparathion 2.0-0.25
Toxaphene-mparathion 2.0-0.25
Endrin-Azodrin 0.25-0.6
Azodrin 0.8
Sevin-Thiodan 0.8-0.5
Methyl parathion 0.5
Endrin-methyl parathion 0.25-0.25
Sevin 2.4
Azodrin 0.6

Endrin 0.4
Toxaphene-DDT 2.0-I 0
Strobane-DDT 2.0-1.0
ChIrocIane-DDT 1.0-1.0
Malathion 2.0

DDT 1.0

TDE 1.0

bamate type insecticides. The present laboratory 
indicate that these materials will not produce ef
field control when used alone or in combinatio
DDT. This is especially true if large populatil
encountered since under these conditions high 
ages of the larvae must be killed if control is‘-

carbons or Sevin must be mixed with appropriate {
ties of methyl parathion or Azodrin if satisfact I
trol is to be obtained. These latter two materi J
appear to be quite effective when used alone
appropriate rates. '

Literature Cited

Abbott, W. S., 1925. A method of computing the eff - '1
an insecticide. J. Econ. Entomol. 18:265-7. v
Adkisson, P. L;, 1964. Comparative effectiveness of seve y,
cides for controlling bollworms and tobacco budworms.
Exp. Sta. Misc. Publ. 709. y II
Adkisson, P. L. and S. J. Nemec. 1965. Efficiency V.
insecticides for killing bollworms and tobacco budwo 
Agr. Exp. Sta. PR-2357. t
Adkisson, P. L., E. S. Vanderzant, D. L. Bull and W. I!
1960. A wheat germ medium for rearing the pink boll 
Econ. Entomol. 531759-62. .~.
Brazzel, J. R. 1962. Toxicity of certain insecticides qr
worms and tobacco budworms. ,Tex. Agr. Exp. Sta. PR p
Brazzel, J. R. 1963a. Resistance to DDT in Heliotbirl
J. Econ. Entomol. 56:571-74. p‘
Brazzel, J. R. 1963b. Effectiveness of several insectici
bollworms and tobacco budworms. Tex. Agr. Exp. Sta. ’
Brazzel, J. R., H. Chambers, and P. J. Hamman. 1961. I
tory rearing method and dosage-mortality data on the 7’
Heliotbis zea. J. Econ. Entomol. 54z949-52. 

Acknowledgments

The research was conducted in cooperation with 
ogy Research Division, U. S. Department of Agti f
technical assistance given by Mrs. Judy Whitley and ‘i
Blanton in conducting these studies is gratefully =--v