Isolation and pathogenicity of naturally-occurring entomopathogenic fungi to unique bark beetle field crop pest

Isolation and pathogenicity of naturally-occurring entomopathogenic fungi to unique bark beetle field crop pest

 

Anis S. Lestari and Sujaya Rao

Oregon State University, Department of Crop and Soil Science, 3017 ALS, Corvallis, OR

The clover root borer (CRB) is a unique bark beetle pest that develops in red clover roots and drastically affects seed production thus causing economic hardship to growers. CRB was earlier controlled with organochlorine insecticides but, ever since these were banned, no insecticide has been labeled for this pest. Entomopathogenic fungi have potential as biological control agents for soil dwelling pests but their impacts on CRB are not known. The objectives of this study were to: 1) Isolate naturally occurring entomopathogenic fungi in red clover fields; 2) Assess the virulence of selected field isolated fungi against CRB. We sampled five red clover fields, and collected over 100 soil samples which were baited with surrogate hosts (waxworms) for detection of naturally occurring entomopathogenic fungi. Of 620 waxworms used as baits, 165 died due to fungal infection. Fungi were then isolated from each waxworm cadaver for identification. Based on the morphology of spore bearing structures, field isolated fungi were identified as belonging to 4 genera - Beauveria, Metarhizium, Isaria and Lecanicillium. Based on ITS sequence data, a subset of 10 isolates were identified to the species level. These include Beauveria bassiana, Isaria fumosorosea and Lecanicillium lecanii. Assessment of the virulence of these isolates when exposed to CRB adults in soil is in progress.