The systemic insecticide imidacloprid is widely used in IPM programs in greenhouses, interiorscapes, landscapes and agricultural crops. Foliar applications of imidacloprid have been shown to kill foraging parasitoids when residue on foliage is contacted, whereas soil applications are considered compatible with biological control, since natural enemies do not come in direct contact with the pesticide. However, many beneficial insects supplement their diet, either by directly feeding on the plant or by feeding on pollen or nectar. This research examined the effects of soil applications of imidacloprid on survivorship and mobility of a flower feeding parasitoid and predator. Anagyrus pseudococci (Girault) (Hymenoptera: Encyrtidae) confined on inflorescences from imidacloprid-treated plants for 1 d showed significantly deceased survivorship at the label and twice the label rate (38 ± 6.7 and 17 ± 4.2% survival) compared to untreated controls (98 ± 1.2% survival). After 1 d parasitoids exposed to the label and twice the label rate displayed trembling (88 and 94% of those surviving) compared to untreated flowers (0%). Residue analysis of nectar showed significant levels of imidacloprid. Coleomegilla maculata (DeGeer) (Coleoptera: Coccinellidae) confined on inflorescences from imidacloprid-treated plants showed significantly decreased survivorship and mobility. In sunflower, survivorship was lower for beetles exposed to imidacloprid at the label rate and twice the label rate (38.3 ± 6.6 and 20.0 ± 6.7% survival) compared to untreated controls (97.5 ± 2.50% survival). These results indicate that imidacloprid used as a soil application is translocated to floral nectar and pollen.
Keywords: biological control
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