IMIDACLOPRID INCREASES EGG-PRODUCTION IN AMBLYSEIUS-VICTORIENSIS (ACARI, PHYTOSEIIDAE)

The chloronicotinyl insecticide, imidacloprid, recommended for aphid c ontrol in Australian stone fruit orchards, was examined for its impact on survival and egg production in Amblyseius victoriensis Womersley. Imidacloprid at the field rate (0.0053% a.i.) was non-toxic, but repel lent to A. victoriensis in laboratory bioassays. Females treated with imidacloprid showed increased egg production, producing 1.9-2.0 eggs p er day compared with 1.3-1.6 eggs per day for the untreated individual s. A population of A. victoriensis in an apricot orchard was significa ntly reduced for 4 weeks following the application of imidacloprid. Ho wever, the population recovered after 5-6 weeks and was significantly larger (more than twice) than that in the untreated section of the orc hard during weeks 9-12. The imidacloprid-mediated enhancement of the f ecundity and population development of A. victoriensis is discussed wi th respect to integration in existing biological control programmes in the Australian stone fruit.