Evaluation of indigenous Beauveria isolates as potential agents for emerald ash borer management and the developmentof a diagnostic marker to monitor a post-release isolate


Abstract: To search for effective and safe indigenous biocontrol agents to manage emerald ashborer (EAB), we conducted a survey in 2008-2009 of entomopathogenic fungi (EPF) infectingEAB in outbreak sites in southwestern Ontario, Canada. Many Beauveria spp. isolates wererecovered from dead and mycosed EAB cadavers residing in the phloem tissues of dead ashbarks, larval frass extracted from feeding galleries under the bark of dead trees. Molecularcharacterization using sequences of the ITS, 5′ end of elongation factor 1 alpha (EF1-α) andintergenic Bloc region fragments revealed that Beauveria bassiana and B. pseudobassiana werecommonly associated with EAB in the sampled sites. Initial virulence screening against EABadults of 23 isolates representing the different clades yielded 8 isolates that produced more than90% mortality in a single concentration assay. These isolates differed in virulence based on LC50values estimated from multiple concentration bioassay and based on mean survival times at aconidia concentration of 2 × 106 conidia ml-1. B. bassiana isolate L49-1AA was significantlymore virulent and produced more conidia on EAB cadavers compared to the other indigenousisolates and the commercial strain B. bassiana GHA suggesting that L49-1AA may have potentialas a control agent against EAB. Studies have been developed to use auto-contamination trappingsystem to disseminate L49-1AA to manage EAB field populations. We targeted the EF1-α genesequence from L49-1AA to develop an allele/strain specific primer set that will be used tomonitor the introduced L49-1AA in terms of its establishment, persistence and virulence in theenvironment.

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