BUREAU OF ENTOMOLOGY AND PLANT QUARANTINE 15 
In Louisiana the use of vine-cutting machines combined with 
disking and plowing after harvest removed the crop remnants that 
serve as a winter food supply for the sweetpotato weevil in infested 
fields. The use of vine cutters prior to harvest facilitated the har- 
vesting of the crop and the subsequent burying of crop remnants. 
COMMODITY CREDIT CORPORATION ASSISTED IN PROTECTION OF LEND-LEASE 
TOBACCO 
Throughout the year the Bureau's workers on stored-tobacco insects 
aided the Commodity Credit Corporation in protecting stocks of leaf 
tobacco purchased by the Government for lend-lease purposes. Sur- 
veys were conducted to find suitable warehouses, warehouses were in- 
spected, a system of obtaining and recording infestation of tobacco 
with the cigarette beetle and the tobacco moth in each warehouse was 
developed, and recommendations were made as to control measures. 
COTTON INSECT INVESTIGATIONS 
Despite serious problems in manufacture and transportation due to 
the war, sufficient supplies of arsenical insecticides, sulfur, and cryo- 
lite were maintained and, although rotenone was not available for 
cotton and the nicotine supply was limited, essential insecticides were 
available for protection of the 1943 cotton crop. Through the cooper- 
ation of State and Federal agencies, growers, and many others, 25,741 
examinations of cotton fields were made to determine current insect 
conditions and the local need for insecticides. This information will 
be of permanent value in determining the need for control and the 
time to apply insecticides. 
Emphasis was given to research that aided the war effort by con- 
servation of materials and manpower. 
BOLL WEEVIL 
The average reduction in cotton yield caused by the boll weevil in 
1943 was estimated at 6.1 percent, as compared with 8 percent in 1942. 
In plots dusted with calcium arsenate at Tallulah, La., the average 
increase in yield over undusted plots was 278 pounds of seed cotton 
per acre, or 13.8 percent, as compared with the 24-year average of 309 
pounds, or 22.2 percent. 
Investigations were continued to determine how increases in cotton 
yields could best be attained from the use of reduced amounts of 
critical materials. Tests on high-yielding Louisiana soils confirmed 
previous findings to the effect that the recommended poundage per 
acre of calcium arsenate could not be materially reduced without 
sacrificing part of the potential gains, and that the largest increase in 
yield per pound of calcium arsenate resulted from delaying the first 
application until 20 to 25 percent of the squares were punctured. Over 
a 4-year period 5 applications beginning with square infestations of 
approximately 25 percent gave as large gains as 7 applications starting 
with infestations of 8 to 15 percent. Experiments have -dsn boen con- 
ducted during the last 5 years comparing control of weevil infestations 
that required 6 applications for complete protection of squares and 
bolls beginning before weevil migration, when 25 percent of the squares 
were infested, with only 3 late applications beginning after weevil 
migration had started. 'The former gave an average increase of 288 
