Abstract

A preventive control program against the boll weevil, Anthonomus grandis Boheman, was applied to a 10-square-mile area within untreated Robeson County, North Carolina, in 1960. The treatment schedule consisted of 4 early-season insecticide applications beginning at the 8-leaf stage of cotton growth plus late-season applications beginning the last week of July and continuing to the end of squaring. Approximately 95% control of overwintered weevils was obtained with the early-season applications, resulting in approximately 88% control of P, boll weevils. When Po boll weevils emerged, control declined steadily to 16% as migrants entered the treated fields and depressed yields. The increase in boll weevils from the overwintered to the peak late season population was 21-fold in untreated fields and 856-fold in treated fields, indicating the magnitude of migration. Nevertheless. 6 insecticide applications increased the average yield of seed cotton 426 lb/acre. More than I bale/acre was produced in 29% of the treated fields and in none of the untreated fields.

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