BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 11 
ers from 12 cotton-growing States, Puerto Kico, and the Bureau. 
The conference report was used in preparing recommendations for 
the control of cotton insects in the various States. Although designed 
primarily for the cotton-growing areas of the eastern half of the 
United States, the conference reports have been translated into French, 
Portuguese, and Spanish for distribution in other cotton-growing 
countries. 
Cotton Leafworm Extends Its Range 
The cotton leafworm was extremely abundant in 1950 and caused 
serious losses in many areas where spraying was inadequate. It 
reached Texas earlier than it had since 1943 and also spread more 
rapidly and over a larger area. Before frost checked its spread, it 
had reached all cotton-growing States except California. 
By the end of June leaf worms were reported in 37 counties in Texas, 
in 1 county in Oklahoma, and in Madison Parish, Louisiana. By the 
latter part of July they had spread to Arizona, Arkansas, and Missis- 
sippi ; in August they reached Missouri ; and in September light infes- 
tations were reported in Alabama, Florida, Georgia, the Carolinas, 
and Tennessee. Heavy applications of insecticides for the control of 
boll weevils in Arkansas, Mississippi, Louisiana, Texas, and Oklahoma 
apparently delayed leafworm outbreaks in many areas. A critical 
shortage of insecticides in August and September kept many farmers 
from controlling the leaf worms, with resulting damage by the worms, 
especially in Missouri, northern Arkansas, northern Texas, and Okla- 
homa. Through the efforts of Federal, State, and extension ento- 
mologists and the insecticide industry, supplies of insecticides were 
diverted to areas where leafworms were doing the most damage. 
Insecticides applied as sprays gave excellent control of cotton leaf- 
worms in experiments near Waco, Tex. Parathion, at dosages of 
0.125, 0.25, and 0.375 pound an acre, gave the most effective control 
and quickest kill of the insecticides tested. It gave complete control 
of a heavy infestation of leafworms within 17 hours. Toxaphene 
at 1.5 pounds an acre gave satisfactory control within 24 hours. 
Aldrin and dieldrin gave good control of small worms of early broods, 
but failed to kill large worms of late broods. The two insecticides, 
when applied at 4- or 5-day intervals against the boll weevil, checked 
developing leafworm infestations, but did not give a sufficiently quick 
kill of large leafworms to save crops from being attacked. 
DDT Still Outstanding for Control of Pink Bollworm 
DDT continued to give better control of the pink bollworm than 
any of the other insecticides tested. Cage tests showed that DDT 
not only reduced the number of eggs laid by the moths but also killed 
a high percentage of first-instar larvae. In a test to determine the 
correct interval between applications, 2 pounds of DDT an acre 
applied at 8-day intervals gave about the same degree of control as 
1 pound of DDT an acre applied at 4-day intervals. Where pink 
bollworms and boll weevils infested the same field, DDT mixed with 
benzene hexachloride, aldrin, dieldrin, toxaphene, or low-lime cal- 
cium arsenate, plus parathion or benzene hexachloride, gave satis- 
factory control of both insects. 
