Potential of starch encapsulated semiochemical-insecticide formulations for adult corn rootworm (Coleoptera: Chrysomelidae) control

Field and laboratory experiments were conducted from 1987 through 1989 to determine if plant-derived semiochemicals and carbamate insecticides, encapsulated in starch-borate (SBM) and pregelatinized-starch (PGM) matrices, could be used to attract and kill corn rootworm (Diabrotica spp.) beetles. D. virgifera virgifera Leconte adults were concentrated in plots within a corn (Zea mays L.) field, following application of SBM granules formulated with semiochemicals and carbaryl. However, resulting mortality was low even though beetles were observed feeding on the granules. Low mortality levels appear to have been caused by a loss of carbaryl during the formulation process. Laboratory assay results indicated that carbaryl, methomyl or carbofuran formulated in the PGM effectively killed D. virgifera adults but only SBM granules formulated with carbofuran provided acceptable mortality. PGM semiochemical-insecticide granules placed in traps killed Diabrotica spp. over time in field corn. D. v. virgifera and D. undecimpunctata howardi Barber mortality in plots treated with starch-encapsulated semiochemical-insecticide granules were comparable to mortality observed in plots treated with a broadcast application of carbaryl (Sevin XLR Plus) while using 90% less insecticide. Mortality of D. barberi Smith & Lawrence was significantly greater in Sevin XLR Plus-treated plots than in plots treated with starch granules. Mortality of the coccinellid Coleomegilla maculata lengi Timberlake was significantly greater in plots treated with Sevin XLR Plus than in plots treated with starch granules, whereas a reverse trend was observed for the carabid Harpalus pennsylvanicus De Geer. Data suggest that efficacy of starch matrix delivery systems may be affected by the interaction of various biotic and abiotic factors but starch matrices appear to have potential as tools that could be used in the development of new, more environmentally sound, corn rootworm management programs.