THE BOLL WEEVIL — LOFTIN 289 



weevil is becoming better acclimated to adverse climatic conditions, 

 though the extent to which this occurs is obscured by animal rein- 

 festation of the border areas by migrating weevils. 



FACTORS INFLUENCING WEEVIL DAMAGE AND USE OF CALCIUM 



ARSENATE 



The great variation in damage from year to year and from region 

 to region depends largely on the number of weevils entering hiber- 

 nation in the fall, the winter survival, and weather conditions dur- 

 ing the growing seasons. Fortunately a large percentage of the 

 weevils fails to survive the winter, for with such a high rate of 

 reproduction it would be unprofitable to raise cotton in much of 

 the infested area. Survival in cages (pi. 9, fig. 1) simulating natural 

 conditions seldom exceeds 10 to 15 percent under most favorable con- 

 ditions; the 15-year average at Tallulah, La., was only 1.22 per- 

 cent in an area where weevil damage is high. Spring emergence from 

 hibernation begins when the daily mean temperature reaches about 

 60° F., or about the same time cotton begins growth, and continues 

 for 2 or 3 months, so that some of the weevils are certain to find 

 squares available for oviposition. Hot, dry weather during the sum- 

 mer kills large numbers of weevil larvae and pupae, while cool, wet 

 weather during June, July, and August is favorable for multipli- 

 cation so that a heavy survival does not necessarily result in heavy 

 damage, or vice versa. Nevertheless information on the relative 

 number of weevils surviving the winter from year to year helps 

 growers in planning control and manufacturers in supplying the 

 insecticides that may be needed. Information on the numbers enter- 

 ing hibernation is obtained by fall examinations of trash and Spanish 

 moss from woods adjacent to cotton fields, and on the survival by 

 spring examinations in the same vicinities. This information is 

 supplemented by determining survival of weevils in hibernation 

 cages in different sections of the Cotton Belt and the overwintered 

 weevils that appear on small plants in the spring. During the war 

 growers and others have also been furnished current weekly infor- 

 mation on the seasonal weevil infestation obtained by a survey of 

 insect abundance conducted cooperatively by State and Federal 

 agencies. 



Many of the more successful growers use calcium arsenate as a 

 regular part of cotton production, but much educational work is 

 needed in acquainting more growers with the value of weevil con- 

 trol and when and how to apply insecticides most effectively. Nearly 

 half of the total cotton is produced by small growers who average 

 less than 10 bales per farm. They often lack the necessary finances 

 for dusting machinery and insecticides. The variation in weevil 



