FIELD-TESTS OF A SEMIOCHEMICAL-BASED TOXIC BAIT FOR SUPPRESSION OF CORN-ROOTWORM BEETLES (COLEOPTERA, CHRYSOMELIDAE)

A semiochemical-based toxic bait for adult Diabrotica virgifera virgifera LeConte and D. barberi Smith and Lawrence was broadcast over three plots (1-3 ha) of maize, Zea mays L. The bait contained an insecticide (0.3% carbaryl), a feeding stimulant (cucurbitacin), and several nonpheromonal volatile attractants (totaling 0.5% of the formulation) in a dry, bran-based carrier. Bait was applied at 7-14 kg/ha (20-40 g [AI] carbaryl/ha). Relative to paired plots that were not treated with bait, numbers of D. v. virgifera and D. barberi counted on maize plants were reduced 77-85% and 55-92%, respectively, 48 h after bait applications. Likewise, relative numbers of D. v. virgifera and D. barberi captured on unbaited yellow sticky traps declined 58-91% and 67-88%, respectively, after applications of bait. Numbers of dead beetles on the ground 24 or 48 h after applications were roughly comparable to reductions in numbers of live beetles counted on plants. Activity of the bait was short-lived in the field, and populations of Diabrotica beetles in treated plots generally returned to near pretreatment levels within 1-2 wk after applications of bait. Although formulations must be improved to enhance activity and longevity, results of this study indicate that semiochemical-based baits for Diabrotica beetles are a potential tool for greatly reducing the amount of insecticide applied in maize production systems.