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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #256194
Title: Diversity of rhizosphere associated entompathogenic fungi of perennial herbs, shrubs and coniferous trees

Author
item FISHER, JOANNA - Oregon State University
item Rehner, Stephen
item Bruck, Denny

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2010
Publication Date: 2/1/2011
Citation: Fisher, J.J., Rehner, S.A., Bruck, D.J. 2011. Diversity of rhizosphere associated entompathogenic fungi of perennial herbs, shrubs and coniferous trees. Journal of Invertebrate Pathology. 106:289-295.

Interpretive Summary: The black vine weevil (BVW) is the key root-feeding insect pest in Pacific Northwest small fruits and ornamentals. Research to develop management strategies for BVW utilizing soil-borne, insect-killing fungi has been ongoing for several decades. Understanding habitat selection of these fungal pathogens is critical to improve their efficacy, persistence, and cost when used as microbial insecticides. This study sought to determine the prevalence of Metarhizium and Beauveria spp. isolated from the rhizosphere (soil in close association to the plant root) of strawberry, blueberry, grape and Christmas tree crops in the Willamette Valley of Oregon. Insect-killing fungi were assigned based on molecular phylogenetic criteria. Four species of Metarhizium were isolated including M. brunneum, M. guizhouense, M. robertsii, and M. pemphigi. Nine Beauveria species were isolated including, Beauveria brongniartii, and eight phylogenetic species of Beauveria. Strawberries and blueberries were significantly associated with M. brunneum and Christmas trees with M. guizhouense and M. robertsii. Grapes were significantly associated with a yet to be named species of Beauveria. All of the Metarhizium isolates screened killed BVW larvae in laboratory bioassays but only M. brunneum and M. robertsii caused significant levels of mortality. The study results suggest that certain species of Metarhizium and Beauveria are significantly associated with the strawberry, blueberry and Christmas tree rhizosphere and could potentially provide better control of BVW.

Technical Abstract: The black vine weevil, Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae), is the key root-feeding insect pest in Pacific Northwest small fruits and ornamentals. Research to develop management strategies for O. sulcatus with soil-borne fungal entomopathogens has been ongoing for several decades. Understanding habitat selection of fungal entomopathogens is critical to improve the efficacy, persistence, and cost of these fungi as microbial insecticides. This study sought to determine the prevalence of Metarhizium and Beauveria spp. isolated from the rhizosphere of strawberry, blueberry, grape and Christmas tree crops in the Willamette Valley of Oregon. Entomopathogenic fungi were assigned to thirteen phylogenetic species based on molecular phylogenetic criteria. Four species of Metarhizium were isolated including M. brunneum, M. guizhouense, M. robertsii, and M. pemphigi. Nine Beauveria species were isolated including, Beauveria brongniartii, an undescribed species referred to as Clade C and seven phylogenetic species of Beauveria. Strawberries and blueberries were significantly associated with M. brunneum and Christmas trees with M. guizhouense and M. robertsii. Grapes were significantly associated with B. bassiana phylogenetic species Bbas-16. All of the Metarhizium isolates screened were pathogenic to O. sulcatus larvae in laboratory bioassays but only M. brunneum and M. robertsii caused significant levels of infection. The study results suggest that certain species of Metarhizium and Beauveria are significantly associated with the strawberry, blueberry and Christmas tree rhizosphere and could potentially provide better control of O. sulcatus.