Life-history parameters of Encarsia formosa, Eretmocerus eremicus and E-mundus, aphelinid parasitoids of Bemisia argentifolii (Hemiptera : Aleyrodidae)

Life-history parameters (juvenile development time, adult longevity, host instar preference and rate of parasitism) offour parasitoids of Bemisia argentifolii (two strains of Encarsia formosa (D and B), Eretmocerus eremicus and Eretmocerus mundus) Were Studied in the laboratory. At 15degreesC juvenile development time was the shortest for E. formosa B (48 days), longest for E. eremicits (79.3 days) and intermediate for E. formosa D (62.8 days) and E. mundus (64 days) at 15degreesC. With increase in temperature, development time decreased to around 14 days for all species/strains at 32degreesC. The lower developmental threshold for development was 11.5, 8.1, 13.0 and 11.5degreesC for E. formosa D, E. formosa B, E. eremicus and E. mundus, respectively. E. formosa D and B, and E. mundus all appeared to prefer to parasitize 3(rd) instar nymphs. The presence of hosts shortened adult longevity in most of the parasitoids, with the exception of E. formosa B, which lived longer than other species/strains irrespective of the presence of hosts. At 15degreesC daily parasitism was very low by all parasitoids. The two Encarsia strains had a constant, but low rate of reproduction during adult life, while the two Eretmocerus species had a very high rate of reproduction when one-day old, which then decreased very quickly. Lifetime fecundity, estimated using a non-linear model, indicated that it was higher for the two Encarsia strains than for the Eretmocerus species. Life history parameters reported in the literature for the four parasitoids are reviewed and compared with Our results. Finally, the potential value for the biological control of whiteflies on greenhouse crops of parasitoids having either a high reproductive rate over a short period (Eretmocerus spp.) or a low rate of reproduction over a long period (Encarsia spp.) is discussed.