Residual Activity of Imidacloprid Controlling Colorado Potato Beetle (Coleoptera: Chrysomelidae) and Three Species of Potato Colonizing Aphids (Homoptera: Aphidae)

Abstract

Field tests done between 1992 and 1994 indicated that imidacloprid applied at 0.03 g (AI)/m to the soil can control overwintered adult Colorado potato beetles, Leptinotarsa decemlineata (Say), and their larval progeny. Summer generation adults colonizing potatoes in treated fields can be controlled by foliar applications of imidacloprid at 50 g (AI)/ha at intervals of 7 d or more. Soil applications of imidacloprid at 0.03 g (AI)An also provided effective control of the potato aphid, Macrosiphum euphorbiae (Thomas); green peach aphid, Myzus persicae Sulzer; and buckthorn aphid, Aphis nasturtii Kaltenbach, for at least 62-65 d after plant emergence. Foliar applications of imidacloprid at a rate of 50 g (AI)/ha required that the aphids be exposed for at least 5 d to attain 50-75% control. Imidacloprid applied in the furrow at a rate of 0.03 g (AI)/m reduced significantly the number of nymphs produced per aphid for each of the 3 species tested early in the season, but not for aphids exposed to plants > 1 mo old. Imidacloprid applied to the soil at a rate of 0.03 g (AI)/m has a long residual activity against Colorado potato beetle adults and larvae, the potato aphid, the green peach aphid, and the buckthorn aphid. This pattern makes imidacloprid an effective control agent for insect pest management on potatoes, but its comparatively slow mode of action may limit its ability to reduce the spread of virus diseases unless the ability of treated aphid vectors to disperse and probe is also reduced.