Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 2001
Publication Date: December 1, 2001
Citation: BEHLE, R.W. CONSUMPTION OF RESIDUE CONTAINING CUCURBITACIN FEEDING STIMULANT AND REDUCED RATES OF CARBARYL INSECTICIDE BY WESTERN CORN ROOTWORM (COLEOPTERA: CHRYSOMELIDAE). JOURNAL OF ECONOMIC ENTOMOLOGY. 2001. v. 94(6). p. 1428-1433. Interpretive Summary: There are many reasons why insecticide applications fail to control the targeted pest including improper insecticide application, development of insecticide resistance, or selection of an ineffective insecticide. The Areawide Management Program for Corn Rootworms (USDA) advocates control of beetles with a reduced rate of insecticide combined with a feeding stimulant, known as cucurbitacin. Concerns have been raised that high beetle populations could consume all of the spray residue before the beetle population is adequately controlled. This study was conducted to determine the amount of dried spray residue containing cucurbitacin that is consumed by rootworm beetles. Results of this study demonstrate that the recommended application rates of the feeding stimulant with reduced rates of insecticide are sufficient to control excessive numbers of beetles. The results of this study support grower usage of baited insecticide applications to target specific pests with reduced rates of the insecticide.
Technical Abstract: A laboratory experiment was conducted to determine the amount of cucurbitacin-based spray residue consumed by adult Western corn rootworms, Diabrotica virgifera virgifera, LeConte. Because commercial applications use small amounts, it is conceivable that a high density of beetles could consume all of the spray residue before economic control is achieved. Dried residue of four treatments were exposed to three groups of 10 rootworm beetles for 1 h each. Treatments consisted of a cucurbitacin-based adjuvant (Cidetrak CRW, Trece, Inc., Salinas, CA) with carbaryl insecticide (Sevin XLR, Rhone Poulenc, Research Triangle Park, NC) mixed at 0, 0.12, 1.2 and 12 g ai/l. For the treatment with cucurbitacin adjuvant only (no insecticide), beetles consumed 0.029 mg beetle-1 h-1. However, when the spray residue contained carbaryl, feeding ceased within 20 minutes and no weight loss of treatment residue was measured. Based on the measurements of this experiment, it is unlikely that the beetles would be able to consume enough spray residue to prevent economic control of the beetle population.