MDA releases thousands of stingless wasps in battle with emerald ash borer

Stingless wasps are being deployed in the war on the emerald ash borer (EAB), according to a press release from the Minnesota Department of Agriculture (MDA). This year, the department released over 182,500 wasps in the Twin Cities metro area and southeastern Minnesota. This is over 5,000 more wasps than the previous four years combined.

The EAB, whose larvae kill ash trees by tunneling under the bark and disrupting the water and nutrient transfer process, is an invasive pest native to Asia and has no known natural enemies in North America.

It was only after years of research that scientists discovered that the stingless wasps, which are produced in the United States Department of Agriculture EAB Parasitoid Rearing Facility, kill ash borer eggs and larvae. This pest control strategy is referred to as biological control, or biocontrol, which pairs an invasive pest with natural enemies.

MDA staff have managed to recover stingless wasps from previous releases (2011 – 2013), and are hopeful that this means the parasitoid wasp population is becoming more self-sustaining.

“The MDA is still early in this process, but we’re excited that we’ve been able to recover parasitoid wasps and are hopeful for long-term success,” said Jonathan Osthus, MDA’s EAB Biological Control Coordinator. “This is the best tool we have at the forest level to combat emerald ash borer.”

Part of the long-term strategy involves identifying new EAB infestations and analyzing them for potential wasp releases. Thus far, Minnesota has confirmed EAB infestations in Anoka, Chisago, Dakota, Fillmore, Hennepin, Houston, Olmstead, Ramsey, Scott, Washington, and Winona counties, and Park Point in Duluth.

Click here to view an interactive map of wasp releases and infested EAB trees in Minnesota.

Photo Credit: Pennsylvania Department of Conservation and Natural Resources, Forestry Archive,


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