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Three species of parasitoid wasps released in Minnesota (Tetrastichus planipennisi, Spathius galinae, and Oobius agrili) are reared at a specialized United States Department of Agriculture (USDA) facility in Michigan. They are provided at no cost to state cooperators, such as the Minnesota Department of Agriculture, for release.
A fourth species, Spathius agrili, was released in Minnesota from 2010 to 2012. Releases of S. agrili were discontinued for northern regions because this species was unlikely to establish.
Release Methods and Locations
Releases began in 2010 in southeastern Minnesota using adult parasitoids. In 2013, to increase parasitoid survival, we began receiving and releasing immature stages of the parasitoids. These immature wasps are placed in protective structures in the field, where they develop and emerge as adults within a few weeks.
There are more than 55 release sites in emerald ash borer (EAB) infested areas of Minnesota. Releases at new and selected existing sites will continue.
View locations of EAB finds and biocontrol agent releases.
Biological Control Releases in Minnesota
Select the "Filter by State" option in the dashboard below and choose Minnesota.
How Biological Control is Implemented
Not all sites fit the criteria for biological control. Once an EAB infestation is identified, several steps need to be completed to determine if biological control is viable:
- Perform a delimit survey of the infestation to identify the perimeter of where symptoms are visible.
- Gauge the intensity or pest pressure in the area based on severity of EAB symptoms throughout the identified visibly infested area. Low to moderate EAB densities are recommended for potential sites.
- Identify forested areas on public or private land within the visibly infested area where removal and/or treatment of infested ash trees will not be feasible. Size and composition of forest should be at least 40 acres and at a minimum include 20 percent ash of varying size class. Ideally, the site would be greater than 25 percent ash and connected to other woodlots.
Once a viable biological control site is identified, the MDA coordinates with local natural resource managers, property owners, and the USDA EAB parasitoid rearing facility.
At each site permission must be obtained from the property owner, guarantee access and ensure other management objectives won’t interfere with implementation. Special permits may be necessary depending on the ownership and designation of land. Long term site access is important for follow-up monitoring of ash health and documenting parasitoid establishment.
