A new study from the University of Minnesota found that several species of parasitic fungi were effective at killing emerald ash borer beetles, one of the most devastating forest pests to ever hit North America.
Funding for this project was provided by the University of Minnesota's Minnesota Invasive Terrestrial Plants and Pests Center, supported by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources.
Decades of research have gone into developing management tools to protect ash trees from emerald ash borer. Ash trees are important in urban areas where they can comprise up to 20% of the urban forest, but they are also a dominant tree in Minnesota's northern marshlands. Additional tools are needed to protect ash trees in these remote areas where other forms of management are less feasible.
One tool which has shown promise at slowing the growth of emerald ash borer populations is the autodissemination device, which traps beetles and coats them with spores of insect-killing fungi. Once covered in spores, the beetles can fly out of the trap and spread spores to one another through mating.
"The idea behind the autodissemination device is to let the beetles do the work. They'd be spreading the spores, infecting their neighbors. This would be especially useful in hard-to-access forests, like the black ash marshes of northern Minnesota," said lead author Colin Peters, a graduate student in the College of Food, Agricultural and Natural Resource Sciences.
University of Minnesota researchers tested ten fungi from Minnesota to assess for their ability to kill emerald ash borer when used in these traps in a lab setting. It is important to study fungi from Minnesota to avoid introducing non-native fungi to the state and because Minnesota fungi are well adapted to local conditions.
Recently published in Forests, the study found:
- All of the fungi used in the study were successful at infecting emerald ash borer beetles.
- The lifespan of emerald ash borer beetles varied depending on which fungus they were exposed to in the trap.
- Three Minnesota-sourced fungi, and one commercially available fungus, reliably reduced emerald ash borer beetle lifespan and were consistently seen sprouting from dead emerald ash borer beetles.
"With a billion ash trees in Minnesota, we need to explore all possible methods to try and control this devastating pest. Laboratory studies show that biological control of the beetle using fungi is possible and the next step is to figure out how to get this to work under field conditions," said co-author Robert Blanchette, a professor in the College of Food, Agricultural and Natural Resource Sciences.
The researchers are now testing the four most successful fungal strains in autodissemination devices placed at sites across Minnesota's state parks and forests, partnering with state and private land managers.
