ARS | Publication request: Effects of Insecticides and Defoliants Applied Alone and in Combination for Control of Overwintering Boll Weevils (Coleoptera: Curculionidae) -- Laboratory and Field Studies

Submitted to: Pest Management Science
Publication Acceptance Date: October 21, 2003
Publication Date: September 1, 2004
Citation: Greenberg, S.M., Sappington, T.W., Elzen, G.W., Norman, J.W., Sparks, A.N. 2004. Effects Of Insecticides And Defoliants Applied Alone And In Combination For Control Of Overwintering Boll Weevils (Coleoptera: Curculionidae) -- Laboratory And Field Studies. Pest Management Science. 60:849-858.

Interpretive Summary: Boll weevils cost the U. S. cotton industry $300 million annually in yield losses. In addition, current management strategies and suppression programs for boll weevils depend on substantial insecticide input. Frequent insecticide applications are expensive and create a risk to the environment. We found that pre-harvest application of insecticides at half rates with conventional cotton defoliants performed as well or better than full rates of insecticides alone. Use of this strategy may reduce late-season boll weevil populations before weevils disperse to overwintering habitats, reduce dispersal of whiteflies and aphids to winter crops, and reduce associated environmental problems.

Technical Abstract: In laboratory, greenhouse, and field tests, we determined effects of combining full rates of defoliants Def 6 and Dropp WP, half rates of the insecticides Karate Z or Guthion 0.2L with the herbicide Harmony Extra, and a combination of half rates of Def and Dropp on the quality of defoliation and mortality of boll weevils, Anthonomus grandis grandis Boheman. Application of a full rate of Def and application of a half rate of Def with a full rate of Dropp both exhibited a toxic effect against boll weevils, while application of a full rate of Def with a half rate of Karate, a full rate of Def with a half rate of Guthion, and a half rate of Def with a full rate of Dropp and a half rate of Guthion provided equal or better control of boll weevil than did a full rate of Guthion or Karate alone. Dropp WP and Harmony Extra alone or in combination with insecticides did not affect boll weevil mortality. Treatment with a half rate of Def and a half rate of Dropp significantly increased defoliation compared to full rates of Def or Dropp alone, and provided adequate defoliation for approximately the same cost per hectare.