A BIOASSAY FOR DETERMINING PATHOGENICITY OF ENTOMOGENOUS FUNGI ON WHITEFLIES

A simple and effective laboratory bioassay method for determining the pathogenicity of entomogenous fungi to whiteflies is presented. The bi oassay is based on characterization of the growth rate and development of entomogenous fungi on fourth instar nymphs of the silverleaf white fly (SLWF), Bemisia argentifolii (Bemisia tabaci, Strain B), and is us eful in determining the effects of environmental factors (e.g., temper ature and humidity) and additives (e.g., surfactants, adjuvants, and p esticides) on the development of entomogenous fungi. Such information can provide a better understanding of the influence of these factors o n the performance of entomogenous fungi when tested under field condit ions. The bioassay has been successfully implemented for the evaluatio n of the pathogenicity of Paecilomyces fumosoroseus, Verticillium leca nii, and Beauveria bassiana against fourth instar nymphs of SLWF. It h as the potential to be useful as a screening tool for determining path ogenicity of new fungal isolates and for the standardization and quali ty control of commercial fungal preparations for viability and virulen ce against insect pests before they are used far field applications. ( C) 1994 Academic Press, Inc.