The effect of vineyard groundcover on the abundance of naturally occurring entomopathogenic fungi isolated using a quantitative Galleria bait method

Abstract

Although sold commercially as myco-insecticides, naturally occurring soil borne entomopathogenic fungi (EPF) pose a unique opportunity for regulating soil-dwelling insect herbivore populations via conservation biological control. Plant identity has a significant effect on soil borne fungi, which may includee EPF. We asked whether the choice of covercrops could affect the diversity and infectivity of EPF in a vineyard. We studied the effect of different mixtures of groundcover vegetation on the infectivity and community composition of the naturally occurring EPF community in a semi-arid vineyard in British Columbia, Canada. Soil was collected from a groundcover field trial and used in a quantitative laboratory bioassay with the model insect, Galleria mellonella. Death by mycosis was greater when Galleria was exposed to soil collected from groundcovers containing native versus exotic grasses. EPF communities isolated from Galleria cadavers also differed among groundcovers. This study presents the first evidence that manipulating vegetative identity can alter the composition and infectivity of soil-dwelling EPF. Future work should investigate the potential for groundcovers and cover crops to increase conservation biological control of soil-dwelling insect pests via changes to EPF communities in specific crop-pest scenarios.