Characterization and virulence of Beauveria spp. recovered from emerald ash borer in Canada

The emerald ash borer, Agrilus planipennis (EAB), is an invasive wood boring beetle that is decimating North Americafs ash trees (Fraxinus spp.). To date, an estimated 30 million ash trees have succumbed to EAB infestation. The current rapid expansion of EAB poses a substantial risk to the remaining ash resources of North America. To find effective and safe indigenous biocontrol agents, we conducted a survey to recover entomopathogenic fungi (EPF) infecting EAB from old outbreak sites within the Province of Ontario, Canada. In each site, mycosed cadavers, larval gallery frass, soil, ash bark, and live beetles were sampled. A number of isolates were cultured from the targeted samples and subsequently characterized with ITS rDNA fragment. The analysis revealed that Beauveria was the most common fungi species associated with EAB habitat. The EAB-recovered Beauveria isolates were further characterized with two nuclear intergenic regions, B-locus and EF1-alpha. Based on phylogenetic analysis, seven of the EAB-recovered Beauveria isolates were selected and check for their pathogenicity and virulence against EAB under laboratory conditions. Four different concentrations viz., 2.0 x 104, 2.0 x 105, 2.0 x 106, and 2.0 x 107conidia/ml were used and compared with the commercial strain GHA. All the EAB-recovered Beauveria isolates were pathogenic to adult EAB and virulence of three isolates viz., L491AA, L11A, and L19C were compatible with the commercial isolate GHA. These 3 isolates also produce more conidia both in vitro and on EAB cadavers compared to GHA, suggesting that these local isolates have better qualities and can be used to control EAB.