Using entomopathogenic fungi to control the greenhouse whitefly (Trialeurodes vaporariorum): developing a standardised bioassay

A standardised bioassay method was created to assess the efficacy of different entomopathogenic fungal isolates against Greenhouse whitefly (Trialeurodes vaporariorum) (GHWF). A spray tower consisting of a gravity feed dual action airbrush attached to an acrylic cylinder and powered by a mini airbrush compressor was calibrated to apply a uniform coverage of solution to a target area. Egg laying by adult GHWF was restricted to a known area of the lateral side of aubergine leaves and migration during the first instar was observed. The spray tower was used to apply a single concentration of eighteen different entomopathogenic fungi (EPF) onto third instar GHWF. Isolates consisted of a mixture of commercially available mycoinsecticides and other isolates taken from the USDA Agricultural Research Service collection, resulting in a mixture of Beauveria, Isaria, Lecanicillium and Metarhizium species. The sprayer delivered 252± 51 fungal spores/mm, equivalent to 2.5 x1012 spores per hectare. Whitefly mortality ranged 8-89% with half of the isolates resulting in <40% GHWF population mortality. The methods employed in this study could be utilised in the selection of isolates for microbial control of whitefly. Combining the sprayer calibration and bioassay method ensures a reliable and applicable approach to test efficacy of whitefly pesticides.