Role of natural enemies and other factors in the dynamics of field populations of the whitefly Siphoninus phillyreae (haliday) in introduced and native environments

Abstract

Abstract The parasitoid wasp Encarsia inaron was introduced from Israel into the US and led to successful biological control of the whitefly Siphoninus phillyreae. The whitefly and its parasitoids were studied in the laboratory and the field in Israel. The results provided additional insight into the process of natural enemy selection for biological pest control. They enabled comparison of (i) whitefly and parasitoid biology and (ii) the role of E. inaron in host population suppression in the two countries. Natural enemies of S. phillyreae other than E. inaron are uncommon in Israel. Laboratory results for S. phillyreae were: mean (± SE) developmental time 23.3(± 16) days; female longevity 26.5 (± 0.3) days; fertility 118 (± 9.6) eggs/female; and survival from egg to adult 41%. For E. inaron, mean (± SE) developmental time was 20.0 (± 0.6) days and net reproductive rates of ca. 11.5 early in the season and 0.2 in September/October. These findings sufficiently resembled those for S. phillyreae and E. inaron in California, to permit comparison between the two systems. In Israel, whiteflies were most abundant in August and their egg to adult survival declined from 19% in May and June to 0.4% in September and October. Unassigned loss of young whitefly nymphs was the largest single mortality factor while mortality caused by E. inaron ranged between 24 and 78%, occurring in both low and high host populations. We discuss the usefulness of parasitoid performance attributes in its country of origin, for the selection of parasitoids for biological control programs.