Submitted to: Pest Management Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 9, 2002
Publication Date: N/A
Interpretive Summary: There is a need for an effective alternative to malathion for controlling boll weevils in cotton in environmentally sensitive areas, and in organic-certified fields. Diatect II is an insecticide that is labelled to use against boll weevils, and is considered acceptable for use in organic fields. In field and greenhouse tests, it was found that Diatect II did not kill boll weevils, but drove a small percentage of them out of the experimental plots. Thus, it does not seem a good candidate to be used as a substitute for malathion.
Technical Abstract: Efficacy of the organic insecticide Diatect II against boll weevil (Anthonomus grandis Boheman) in cotton (Gossypium hirsutum L) in the Lower Rio Grande Valley of Texas was assessed in small field plot trials and greenhouse cage tests using azinphos-methyl treatments as a standard for comparison. Plastic sheets were placed in the furrows of the treated plots sto retrieve boll weevils, which dropped from the plants after being killed by the insecticides. Samples of live weevils taken by tractor-mounted vacuum revealed a modest, but significant, reduction in boll weevil populations in Diatect II plots. However, samples of dead weevils indicated that this reduction was due to movement of weevils out of the plots rather than to mortality. This interpretation is supported by greenhouse cage studies where mortality in Diatect II treated cages was no greater than that in untreated control cages. The effects of insecticide treatments in small plots can be confounded easily and quickly by interplo movement of target insects. Although the relative effects of various compounds can usually be assessed by sampling the populations in plots soon after treatment, the best measure of efficacy is obtained by directly sampling insects that have died in the plot. This parameter is insulated from the effects of interplot movement, unless the toxicant is slow to immobilize the target insect.