Further Studies of Integrated Control Methods against the Egyptian Alfalfa Weevil in California 123

Abstract

The alfalfa weevil, Hypera postica (Gyll), and the Egyptian alfalfa weevil, H. brunneipennis (Bohemian), are minor pests on alfalfa in California. Chemicals of indiscriminate toxieity directed against these two minor pests could initiate more serious pest problems in alfalfa. Several insecticides were evaluated for their effect on the Egyptian alfalfa weevil, on Bathyplectes cruculionis (Thoms.), a parasite of the two weevils, and on other parasites and predators of field crop pests. Heptachlor at low dosages of fl to 2.4 ounces per acre gave effective control of the two weevil larvae but had little effect on B. curculionis. At these low dosages heptachlor had little effect on Hippodamia conrergens G.-M. and Orius tristicolor (White) but had II moderate effeet on Trioxys utilis Mues., a parasite of the spotted alfalfa aphid (Therioaphis maculate (Buckton)), and on Chrysopa spp., and Nabis ferus (Linn.). Demeton which is used to control aphid pests in alfalfa hay and seed in California, had little or no effect on the Egyptian alfalfa weevil larvae. It had a moderate effect on the weevil parasite B. curculionis and on N. ferus and O. tristicolor and it had a slightly greater effect on T. utilis and H. convergens. The biotic insecticide, Bacillus thuringiensis Berliner, had little, if any, effect on the Egyptian alfalfa weevil larvae and on the beneficial insects studied in these tests.