Canadian Forest Service Publications

Virulence of the entomopathogenic fungus Lecanicillium (Deuteromycota: Hyphomycetes) to Pissodes strobi (Coleoptera: Curculionidae) 2006. Kope, H.H.; Alfaro, R.I.; Lavallée, R. The Canadian Entomologist 138(2): 253-262.

Year: 2006

Issued by: Pacific Forestry Centre

Catalog ID: 26208

Language: English

Availability: PDF (download)

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The widely occurring fungal genus Lecanicillium Zare & W. Gams (formerly Verticillium) includes species that are pathogenic to insects. We collected 27 Lecanicillium isolates from soil and from dead adult Pissodes strobi (Peck) in British Columbia, Canada, and assessed their virulence against this host. Eighteen isolates were identified as L. longisporum (Petch) Zare & W. Gams and six as L. muscarium (Petch) Zare & W. Gams, while three isolates could not be identified to the species level. We assayed a subset of these isolates (14 L. longisporum, 3 L. muscarium, and 1 Lecanicillium sp.) as well as the fungal component of the commercial products Mycotal® (L. muscarium) and Vertalec® (L. longisporum) and a herbarium isolate (Lecanicillium sp.). When adult weevils were inoculated with a conidial suspension (1 × 107 conidia/mL), mycosis-related mortality at the end of a 17-day incubation period varied between 20% and 100%, depending on the isolate tested. Eight of the isolates killed >75% of weevils: a Lecanicillium sp. isolate, PFC19, which displayed the lowest LT50 value; five indigenous L. longisporum isolates; and both commercial products. In a goodness-of-fit test comparing isolate virulence among species, the unidentified PFC19 isolate was found to be more effective than either L. longisporum or L. muscarium, while L. longisporum caused somewhat greater mortality than L. muscarium. In a similar analysis, isolates extracted from soils tended to be more effective than those obtained from cadavers. Horizontal transmission to live P. strobi was observed using different isolates of Lecanicillium species. Notwithstanding the variability in virulence, the indigenous Lecanicillium species that we isolated and assayed are confirmed as pathogenic to P. strobi in British Columbia.