56 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE, 1952 
1950. It survived throughout Oklahoma and Arkansas and also in 
parts of Tennessee. North Carolina, and Missouri, 
Cotton insect investigations were continued at Bureau laboratories. 
Much of the work was in cooperation with agricultural experiment 
stations in the respective States in which the work was done. 
Insecticides for Cotton Insects Screened at Texas Laboratory 
Promising new insecticides tested at the basic research screening 
laboratory m Texas against the boll weevil and other cotton insects 
included endrin, isodrin. methyl parathion, Metacide, malathon, 
compound 1795, compound Q-129, insecticide 3960- XI t. and dimethyl 
potasan. Field tests with several of these new insecticides were in 
progress in 1952 to establish satisfactory dosage level-. 
In early-season control experiments in Texa< 7,000 acres of cotton 
were treated with sprays containing either toxaphene or aldrin. Four 
applications were made between May 14 and June 9. The seasonal 
boll weevil infestation in the treated fields averaged 3 percent as 
compared to 20 percent for an adjacent untreated area. Bloom counts 
showed that early-season treatments had greatly accelerated fruiting. 
Light Bollworm Damage to Cotton Crop 
Comparatively light damage to the cotton crop from the bollworm 
occurred in 1951 although serious localized outbreaks were reported. 
especially in Arizona, Mississippi, Texas. Oklahoma. Louisiana, and 
Arkansas. A severe outbreak of various lepidopterous larvae, chiefly 
the bollworm, HeliotMs armigera (HbiO. and the tobacco budworm 
Ihlhifhh virescens (F.), was reported in Mississippi during the latter 
part of June and July. In both Mississippi and South Carolina the 
tobacco budworm was more abundant on cotton than the bollworm. 
In Mississippi the bollworm was more abundant on alfalfa and milo 
than on any other crops, indicating that they may be of value as 
trap crops. 
DDT continues to be the most effective insecticide yet known for 
the control of the bollworm. It may be used in mixtures with other 
insecticides where other insects, as well as bollworm, require control. 
In tests in Mississippi, DDT applied at <>.:> pound per acre when the 
bollworm eggs were hatching was sufficient to give effective control. 
After the bollworms were large and had entered the bolls 
higher dosage- were required. Toxaphene proved to be the next most 
effective insecticide againsi the bollworm. Toxaphene applied as a 
Jim gave better control of bollworms than toxaphene -pray. Boll- 
worm cont rol was improved where I )1 )T was added to toxaphene spray 
mixture at the rate of 0.25 t<> L.O pound per acre. Bollworms were 
usually controlled where 0.5 pound or more of DDT per acre was ap- 
plied with benzene hexachlonde, aldrin, dieldrin, heptachlor, or toxa- 
phene in the regular schedule for boll weevil control. 
In Texas no control measures were needed for the bollworm in fields 
mi which early treatment for Other injurious insects did not extend 
beyond dune L5. Bollworm egg deposition was heavy in many of 
these field- but beneficial insects were abundant and prevented the 
development of damaging infestations. In these experiments the 
natural enemies of the bolTworm appeared to have had ample time to 
