could not survive if it were not permitted to develop on cotton. The boll weevil is a key 

 species on cotton. Except for early stalk destruction in limited areas, insecticides now 

 provide the only effective way to achieve control. The necessity for using insecticides 

 to control this insect complicates the control of other cotton pests, including the boll- 

 worm complex (Heliothis spp. ), spider mites, and aphids. In view of the extensive 

 losses caused by the insect, the adverse effects of insecticides on beneficial insect 

 parasites and predators and on pollinating insects, and the large amount of insecticides 

 that are applied in the environment in connection with its control, the Entomology 

 Research Division has oriented its research program to develop a method, or combi- 

 nation of methods, that can be employed to eliminate the insect from the United States. 



Because of the extensive losses that it causes, and the growing concern over the 

 side effects produced by the insecticides employed each year for its control, it is 

 apparent that it would be profitable to the cotton industry and to the Nation as a whole to 

 invest large sums of money to achieve complete elimination of the boll weevil. 



Significant Features About the Boll Weevil That Have a Bearing on the 

 Feasibility of Emploving Sterile Insects for Population Control 



The total number of boll weevils in the infested areas , even during their periods 

 of greatest scarcity, is very large. Nevertheless, after extensive analysis of the boll 

 weevil problem, it has long been the view of the writer that the population density per 

 unit area is relatively low in comparison with many other economic pests. There is 

 good evidence that the initial population of the insect in the spring, after hibernation, 

 can be expected to average about 200 boll weevils per acre. Much of the acreage could 

 be expected to have higher populations, but there is probably more acreage where the 

 population would average substantially less than 100 per acre. Reasonably effective 

 methods of chemical fcontrol have been developed through intensive research by State 

 experiment stations, Federal research institutions, and industry. Cultural control 

 methods are useful in limited areas. Thus, it is possible, and practical, to reduce the 

 population to low levels per unit area. This was demonstrated in early research with 

 chlorinated hydrocarbon insecticides by K. P. Ewing— and C. R. Parencia of the 

 Entomology Research Division. It is common practice, as a result of their work and 

 that of entomologists with various other Federal and State laboratories, for farmers to 

 employ about four insecticide treatments when the insect is emerging from hibernation 

 to reduce the overwintered population. Such treatments, properly timed, probably 

 reduce the surviving, overwintered population by 90 percent. More recent studies by 

 the Entomology Research Division have been conducted for the purpose of determining 

 as precisely as possible the extent of reduction that is feasible and practical in the 

 spring by applying about six properly timed treatments. These studies, conducted in the 

 vicinity of Tallulah, La. , and Florence, S. C. , indicate that the spring population can 

 be reduced by 95 percent or more. Thus, an intensive spring- treatment program can be 

 expected to reduce the population to an average of about 10 or less boll weevils per acre. 



2_/ Retired. 



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