Effects of Aschersonia aleyrodis on the life table and demographic parameters of Bemisia tabaci

Abstract

The present study reports the sublethal effects of the entomopathogenic fungus, Aschersonia aleyrodis (Webber) on Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae). A fungal suspension of A. aleyrodis isolate Aa005 containing 1×107 conidia mL−1 was sprayed against B. tabaci on eggplant leaves under greenhouse conditions. The effects of fungal application on survival as well as life table parameters of the whitefly were observed at different post inoculation periods. The results indicated that A. aleyrodis can significantly affect the survival of 1st, 2nd, and 3rd nymphal instars of B. tabaci. Developmental periods of different instar nymphs were not affected by fungal application. A. aleyrodis spores persisted well and significantly affected the survivorship of young instar nymphs of B. tabaci at different post incubation periods. Life table results suggested that A. aleyrodis has no impact on general fecundity and longevity of B. tabaci. When the pathogen was exposed to the open environment and maintained for a relatively longer period, a reduction in the reproductive rate and intrinsic rate of increase was caused by the fungal spores, though the sublethal effects were not as good as the control treatment. The results suggest that the ability of spores to suppress an increase in whitefly population persists well after incubation of spores to the external environment (up to 9 days).