Efficacy and persistence of two microbial control agents of Xylosandrus germanus

First detected in the U.S in 1932, the ambrosia beetle Xylosandrus germanus Blandford (Coleoptera: Curculionidae) is a generalist woodborer native to Asia attacking a wide range of host trees. This wide host range is likely facilitated by the broad range of its symbiotic fungus, Ambrosiella hartigii. Despite being considered a secondary pest, X. germanus also attacks apparently healthy host trees and so is increasingly being recognized as a key pest of nursery trees. The goals of the current research are to 1) determine beetle survival and reproductive success following application of control agents and 2) evaluate persistence of microbial control agents in the environment. We tested two microbial control agents including Metarhizium brunneum strain F52 (Met52, Novozymes, Inc.), which directly affects the foundress and thus indirectly affects gallery formation and offspring, and Trichoderma harzanium strain T-22 (Rootshield, BioWorks, Inc.), which directly affects the symbiotic fungus and thus indirectly affects the beetles.  Efficacy was evaluated by spraying American beech (Fagus grandifolia) sapling bolts with the control agents and measuring variables such as foundress survival, gallery length, and offspring survival. Persistence was tested by spraying control agents on beech sapling bolts, placing them in shaded and sunny environments, and taking samples at designated time intervals. Results from this research will show the potential of these entomopathogenic and mycoparasitic fungi for management of X. germanus populations.