Microbial control of Agrilus planipennis (Coleoptera: Buprestidae) with Beauveriabassiana strain GHA: field applications

Abstract

The effects of Beauveria bassiana strain GHA, applied as BotaniGard ES, on newly colonised and well-established populations of emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae) were evaluated in the field using foliar and trunk sprays in Michigan in 2004–2005. Results from field trials at a newly colonised white ash site showed a 41% reduction in A. planipennis population in fungal-treated trees compared with that of untreated controls. In addition, fungal infection was also found in 20% of the larval population within 14 days of incubation under laboratory conditions. At a site with a well-established Agrilus planipennis population in green ash trees, larval density was reduced by 47% for trees treated with the fungus compared with that of the controls; 21% of larvae from the current generation were found infected after 14 days of laboratory incubation. Fungal-treated green ash trees also produced fewer adults emerging in the next generation, with a 63% reduction in adult density observed in treated trees compared to that of controls. As a result, fungal-treated trees sustained 42% less crown dieback than did controls. A. planipennis larval density was negatively correlated with trunk height above the ground, and positively correlated with log diameter. Results of laboratory leaf bioassays on A. planipennis adults showed that fungal conidia persisted well under field conditions, with mortality of 78–100% at 7 – days post – exposure for leaves collected between 2 and 264 h after application. Potential strategies for using B. bassiana strain GHA for managing A. planipennis are discussed.

Keywords:

• emerald ash borer
• Agrilus planipennis
• Beauveria bassiana strain GHA
• conidial persistence
• field applications
• microbial control

¹This article reports research results only. Mention of a proprietary product does not necessary constitute an endorsement or a recommendation for its use by Michigan State University or US Department of Agriculture.

¹This article reports research results only. Mention of a proprietary product does not necessary constitute an endorsement or a recommendation for its use by Michigan State University or US Department of Agriculture.

Acknowledgements

We thank D.L. Miller, C. O'Connor, K. Robinson (USDA Forest Service, Northern Research Station) for field assistance; E. Nemur, (Fox Hills Country Club, Plymouth, MI) for use of the green ash plantation; City of Ann Arbor, MI, for use of space to plant our experimental plot of white ash trees; B. Levene (Emerald BioAgriculture Corp., MI) for supplying BotaniGard ES products; T.M. Poland (USDA Forest Service, Northern Research Station) and G. Zimmermann (Federal Biological Research Centre for Agriculture and Forestry, Institute for Biological Control, Darmstadt, Germany) for comments on an earlier version of the manuscript. Valuable comments by two anonymous reviewers are also greatly appreciated. This research was partially funded by USDA Forest Service, North Central Research Station, Research Joint Venture Agreement 03-JV-095.

Notes

¹This article reports research results only. Mention of a proprietary product does not necessary constitute an endorsement or a recommendation for its use by Michigan State University or US Department of Agriculture.