Impact of Beauveria bassiana (Ascomycota: Hypocreales) on the small southern pine engraver (Coleoptera: Scolytidae) in a loblolly pine bolt assay
The small southern pine engraver, Ips avulsus Eichhoff (Coleoptera: Scolytidae), is one member of a guild of southern pine bark beetles that causes millions of dollars of losses to southern U.S. pine forests annually. Our objective was to determine the impact of a commercial preparation of the entomopathogenic fungus Beauveria bassiana (Balsamo-Crivelli) Vuillemin (Ascomycota: Hypocreales) in protecting pine host plant tissue from colonization and damage by I. avulsus and on the B. bassiana–induced mortality of I. avulsus adults during the first 2 wk of host attack. The field trials were conducted in the Kisatchie National Forest (Rapides Parish, LA) using a small-bolt technique. Results showed that the I. avulsus adults successfully colonized both the B. bassiana–treated bolts and the control bolts within the first week of field exposure. Although the formulation did not protect bolts from attack, it caused significantly higher mortality of I. avulsus adults in B. bassiana–treated bolts than in the control, and significantly reduced the number of adults that reemerged. Approximately 84% of I. avulsus adults found in the B. bassiana–treated bolts died from B. bassiana infection and never reemerged, compared to 14% in the control bolts. Although effects from B. bassiana were too late to stop I. avulsus from entering host bolts, the high rates of beetle mortality observed under the bark suggest potential utility of the formulation for managing pine bark beetles. Successful application strategies and tactics are unknown at this point and will depend on many factors, including deployment techniques.