Diflubenzuron for Control of the Boll Weevil in Unisolated Cotton Fields123

Abstract

In a 1976 test in unisolated cotton fields, different rates (35, 70, and 140 g AI/ha) of the insect growth regulator diflubenzuron, N -[[(4-chloropheny)amino]carbonyl]-2,6-difluorobenzamide, were applied aerially over a 6-wk period to suppress populations of Anthonomus grandis Boheman. There was a pronounced dosage rate response to the chemical in that the percentage emergence of adult weevils from cotton squares collected from treated fields averaged 37.7, 22.2, and 15.8% at the lowest, median, and highest rate, respectively. Adult emergence from squares collected in untreated control plots averaged 70% during the same period. The reduction in weevil emergence was most pronounced in the F1 generation and somewhat less in the F2 and F3 generations. A similar emergence pattern was observed in 1977 but due to a delay in the initial treatment the effect lagged by 1 generation. In both years, there was an apparent rebound by pest populations during the latter part of the season as indicated by increased emergence from the field collected squares. This result was attributed to movement of untreated weevils into the treated fields.