Microbial control of emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae) with Beauveria bassiana strain GHA: Greenhouse and field trials

In 2003–2004, the lethal and sublethal effects of Beauveria bassiana strain GHA on emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae) adults and larvae were evaluated using topical spray and fungal band treatments in the greenhouse and field. B. bassiana strain GHA was moderately effective against A. planipennis adults in greenhouse studies. However, efficacy was improved in the field when B. bassiana was sprayed directly on trunk surfaces prior to adult emergence. In the greenhouse, adult infection rates ranged from 27.7% to 33.5% depending on the application rates that ranged from 25 to 75 × 1013 conidia/ha, whereas in the field, adult infection rates ranged from 58.5% and 83% at two application rates of 10 and 100 × 1013 conidia/ha. The sublethal effects of B. bassiana strain GHA was observed on A. planipennis adults and larvae surviving exposure to sprayed ash trunks. The adult longevity of females and males was significantly reduced by ca. 9 and 13 d, respectively; females also laid fewer eggs and larval development was prolonged. The use of B. bassiana strain GHA-fungal bands resulted in ca. 32% mortality of A. planipennis adults compared to ca. 1% for control adults. In addition, B. bassiana strain GHA trunk sprays in the fall resulted in ca. 8% mortality of A. planipennis under the bark of infested ash trees, compared to 1.6% mortality in the controls. Larval infection rate was positively correlated with larval density in the field. The development of B. bassiana strain GHA as a management tool for A. planipennis in North America was discussed.