Research on ovicidal fungi and Emerald Ash Borer demonstrates biocontrol potential

Pictured above: A scientist puts Emerald Ash Borer eggs into individual wells. 

Invasive Emerald Ash Borer (EAB) beetles have killed hundreds of millions of North American ash trees, including large numbers throughout Minnesota. Entomopathogenic fungi (or, fungi with the ability to infect and kill insects) have potential to play a big role in pest management solutions, as demonstrated by new research from CFANS’s Sofia Simeto, Bob Blanchette, and Ben Held in collaboration with David Showalter of the Oregon Department of Forestry and Kathryn Bushley of USDA-ARS in Ithaca, NY, and funded by the Minnesota Invasive Terrestrial Plants and Pest Center (MITPPC) which receives support from the Minnesota Environment and Natural Resources Trust Fund. 

Using entomopathogenic fungi for insect population control is a broadly established method, but prior to this study, no research has been available specifically about fungi’s impact on EAB in the egg stage. In order to determine impacts of specific fungi on EAB, Simeto and colleagues tested fungal strains that had been collected and isolated from EAB’s galleries on ash, by growing them in cultures in a lab and applying them to EAB eggs, which were then analyzed. All fungal treatments were tested at least twice against EAB eggs.

This analysis of pathogenicity of fungal strains found in EAB galleries demonstrated consistent ovicidal effects of these fungi on EAB eggs. Observations included unhatched eggs, eggs developing mycelia along the outside, and even mycelia developed on larvae of some eggs that hatched — a complete review of results can be seen in Section 3 of the publication in Forests. Additionally, high levels of inoculum were recovered from both EAB eggs and larvae showing the success of the infection and demonstrating that even after emergence, larvae were infected. 

The proven possibility of disrupting EAB’s life cycle at these early stages represents a potential management opportunity. With this knowledge, further research can explore opportunities to use entomopathogenic fungi as part of integrated pest management approaches for EAB in North America, with potential to reduce beetle populations and preserve ash trees.

Citation: Simeto, S.; Held, B.W.; Showalter, D.N.; Bushley, K.E.; Blanchette, R.A. Ovicidal Effect of Entomopathogenic Fungi on Emerald Ash Borer,Agrilus planipennis Fairmaire, Eggs. Forests 2024, 15, 2170. https://doi.org/10.3390/f15122170