Submitted to: Corn Rootworm Areawide Management Program
Publication Type: Abstract only
Publication Acceptance Date: 9/15/2002
Publication Date: 10/30/2002
Citation: Weber, D.C., Athanas, M.M., Martin, P.A. 2002. Optimizing selective baits for diabrotica. Corn Rootworm Areawide Management Program. Interpretive Summary:
Technical Abstract: Baits for adult corn rootworms, Diabrotica spp., have been formulated using two cucurbitacin-containing plants, buffalo gourd and bitter mutant of Hawkesbury watermelon. Cucurbitacins are strong arrestants and feeding stimulants for chrysomelid leaf beetles, including corn root worms, which are estimated to cost $1 billion of damage in the USA alone. Cucurbitacins are repellant to other insects and to vertebrates. They are too expensive to synthesize for agricultural applications, the preferred sources being parts of the cucurbit plants themselves. We aim to optimize the selectivity of these baits for the target insects by varying the cucurbitacin and toxin types and concentrations. Our goal is to maximize efficacy while minimizing non target toxicity and bait cost. Almost all bait applied in US cornfields has been mixed with carbaryl or methyl parathion as toxicants. In USDA-ARS area wide programs in Midwestern USA, these active ingredients were applied at 10% of the labeled rate for foliar applications, resulting in significant reduction of pesticide inputs for Diabrotica adult suppression. However, the non-selective contact activity of these neurotoxins, as well as the appearance of pest resistance, makes the development of alternative lower-risk toxins imperative. Candidates are spinosad and borates, both of which have shown good control in laboratory and field assays; a new strain of Chromobacterium is also under investigation as a bait component. In addition to the two commercially-available feeding stimulants, other cucurbit species are under investigation in North and South America which may perform better as baits at lower cucurbitacin concentrations, thus reducing bait costs. However, any bait must maintain sufficient levels of cucurbitacins for repellence to protect non target beneficial insects. Cucurbitacin baits which are optimized for target efficacy, ecological selectivity, and reasonable cost, should have a major role in control of Diabrotica and related chrysomelid pest genera in crops systems of North and South America and Eurasia.