The three species of parasitoid wasps released in Minnesota (Tetrastichus planipennisiSpathius galinae and Oobius agrili) are reared in a specialized USDA facility in Michigan. They are provided at no charge to state cooperators such as the Minnesota Department of Agriculture to release. A fourth species, Spathius agrili, was released in Minnesota from 2010 – 2012. Releases of S. agrili were discontinued for northern regions because this species was unlikely to establish.

We initiated releases in 2010 in southeastern Minnesota with adult parasitoids. To increase the efficiency of parasitoid rearing we began receiving and releasing immature stages of the parasitoids in 2013. They are in protective structures that are placed in the field then the adult wasps emerge within the next few weeks. There are now over 30 release sites in the Twin Cities and southeastern Minnesota. Releases at new and select existing sites will continue. View locations of EAB finds and biocontrol agent releases.

Coordination

After a viable biological control site is identified, coordination by the MDA with local natural resource managers, property owners and the USDA EAB Parasitoid Rearing Facility are necessary. At each site one has to obtain permission, 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.

Site Suitability:

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:

  1. Perform a delimit survey of the infestation to identify the perimeter of where symptoms are visible.
  2. 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.
  3. 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% ash of varying size class. Ideally, the site would be greater than 25% ash and connected to other woodlots.

 

Biocontrol agent
2010
2011
2012
2013
2014
2015
2016
2017
All
Tetrastichus planipennisi
2,154
19,480
19,822
45,579
34,434
151,022
45,288
43,245
358,024
Oobius agrili
0
3,641
10,241
8,597
12,062
31,490
42,600
23,100
131,731
Spathius galinae
0
0
0
0
0
0
1,613
2,151
3,764
Spathius agrili
1,172
7,596
15,258
0
0
0
0
0
24,026
Totals
3,326
30,717
45,321
51,176
46,496
182,512
89,501
68,496
517,545