Development of Populations of the Boll Weevil in Fields Treated with Various Insecticides During 1959, 1960, and 19611

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Abstract
Seasonal populations of boll weevils, Anthonomus grandis Boheman, were carefully sampled in a number of small cont iguous cotton fields where control programs with different inticides were being conducted. Records were also made of cotton fruiting and fruit damage by weevils in these fields and in untreated control areas to determine the relationships between boll weevil numbers, abundance of fruit, and boll weevil damage, as well as the effectiveness of the insecticidal programs. The organophosphorus compounds were generally more effective for the control of overwintered weevils than the other types of insecticides used, but continued emergence of boll weevils after squaring began during 1960 and 1961 reduced the effectiveness of programs depending on a single application for the control of overwintered weevils. Continuously high populations in the untreated areas resulted in greatly reduced boll set, but the emergence of large numbers of weevils in the treated fields which increased square damage temporarily did not reduce boll set. However, in the treated areas higher percentages of punctured Squares were usually followed by higher percentages of weevil damaged bolls. The rate of population increase from generation to generation and the amount of damage caused by each weevil depended to a great extent on the numbers of squares on the cotton and the intensity of competition for those squares. In untreated fields during 1960 and 1961 first generation increases over overwintered populations were about S-fold and 2-fold respectively.

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