CITRUS LIMONOID EFFECTS ON COLORADO POTATO BEETLE (COLEOPTERA, CHRYSOMELIDAE) COLONIZATION AND OVIPOSITION

The effects of citrus limonoids, applied topically to potato foliage, on colonization and oviposition by Colorado potato beetle, Leptinotars a decemlineata (Say), adults were quantified in no-choice laboratory a ssays, choice and no-choice greenhouse arena observations, and small-p lot field tests. In laboratory assays the oviposition rate decreased w ith increasing limonoid dosage and exposure time. Oviposition suppress ion time also increased with increasing dosage. Over a 9-d observation period, ED(50)s (50% reduction in fecundity) were 7.2 mg/ml, 1.93 mg/ ml, and 0.64 mg/ml for 3-, 6-, and 9-d exposures, respectively. Adult colonization and oviposition rates were significantly reduced by limon oid treatment in both greenhouse and field tests. The seasonal density of adults was significantly reduced with a low rate (3.6 kg/ha) appli cation of limonoids, whereas a higher application rate (10.8 kg/ha) wa s needed to reduce significantly the seasonal egg mass density in the field. The total number of treatment applications (1, 2, or 3) made at 3-d intervals significantly lengthened the period during which coloni zation and oviposition were inhibited, but did not affect seasonal den sities of either adults or egg masses. These results indicate that cit rus limonoids have very good potential for use in pest management.