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Title: Virulence of Beauveria bassiana and Metarhizium anisopliae (Ascomycota: Hypocreales) commercial strains against adult Xylosandrus germanus (Coleoptera: Scolytidae) and impact on brood

Author
item CASTRILLO, L. A. - Cornell University
item Griggs, Michael
item Ranger, Christopher
item Reding, Michael - Mike
item Vandenberg, John

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/19/2011
Publication Date: 8/1/2011
Citation: Castrillo, L., Griggs, M., Ranger, C.M., Reding, M.E., Vandenberg, J.D. 2011. Virulence of Beauveria bassiana and Metarhizium anisopliae (Ascomycota: Hypocreales) commercial strains against adult Xylosandrus germanus (Coleoptera: Scolytidae) and impact on brood. Biological Control. 58(2):121-126.

Interpretive Summary: The Asian ambrosia beetle Xylosandrus germanus is an invasive nursery pest that has been known in North America for more than 70 years. Recently they have become significant pests of many species of nursery trees in several states. We are working to develop biological control options for this pest. We tested its susceptibility to two species of insect-pathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, in laboratory assays. Treatment of adult females did not affect their tunneling activity, but resulted in reduced gallery formation and reduced production of offspring. Among the batches of offspring produced by treated females, 27 to 100% had fungal infection in some or all progeny. Infection was observed among larvae, pupae and adult progeny. These data suggest that the impact of fungal spray applications extends beyond the treated parent and that infection in the brood chamber could significantly affect beetle populations in the field.

Technical Abstract: The ambrosia beetle Xylosandrus germanus is an invasive pest with a wide host range and is a serious pest of orchards and nurseries in the eastern US. In this study we evaluated the potential of entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae as control agents against this beetle. Three commercially available strains of these fungi were assayed against adult females to determine their virulence and their impact on brood production. Among the three strains tested, B. bassiana Naturalis and M. anisopliae F52 were more virulent than B. bassiana GHA. Mortality observed 7 days post spray was 8.8 +/- 5.9%, 92.7 +/- 7.1% and 88.75 +/- 7.2% for GHA, Naturalis and F52, respectively, at a dose of approximately 600 conidia/mm2. Treatment of adult females did not affect their tunneling activity, but resulted in reduced gallery formation, brood production and brood numbers. Among the broods produced by treated females, 27 to 100% had fungal infection in some or all progeny. Infection was observed among larvae, pupae and adult progeny. These data suggest that the impact of fungal spray applications extends beyond the treated parent and that infection in the brood chamber could significantly affect beetle populations in the field.