Screening potential entomopathogenic fungi for the control of the greenhouse whitefly (Trialeurodes vaporariorum)

Abstract

Greenhouse whitefly (Trialeurodes vaporariorum) (GHWF) are a globally important pest, causing significant damage to >250 plant species by consuming sap, secreting honeydew and transmitting viral plant diseases. Entomopathogenic fungi (EPF) are being developed for biological control of whitefly in integrated pest control strategies which include reducing chemical applications and increasing the use of sustainable alternatives. Whitefly have piercing-sucking mouthparts, therefore EPF are the most promising microbial natural enemies to be exploited for whitefly control as they can infect directly through the integument. Temperature conditions within temperate greenhouses vary from 10 to 35°C which presents a challenging abiotic environment for EPF and impacts greatly on pest mortality. EPF used as biological control for GHWF need to be highly virulent and work across a range of temperatures, therefore, we compared temperature profiles of eighteen EPF originating from temperate, subtropical or tropical regions. In vitro germination, growth and spore production experiments were conducted as well as an investigation into the pathogenicity of these EPF isolates to third instar greenhouse whitefly using a novel standardised bioassay design, with a bespoke benchtop sprayer. Using the data collected, we were able to rank isolates based on growth rate, germination and spore production at a range of temperatures to select those with distinctive temperature profiles. The methods employed in this study could be utilised in the selection of isolates for microbial control of whitefly and in particular, selecting pathogens to be co-applied with the potential to improve virulence or cause an increase in workable climatic conditions