Thousands of small, non-stinging wasps released in Blackhawk Park

The Minnesota Department of Agriculture has released three types of small, non-stinging parasitoid wasps to help reduce emerald ash borer in Blackhawk Park in Eagan.

Biocontrol releases began June 13 and will take place bi-weekly until mid-September.

This is the first year biocontrol has been done in Eagan.

The amount of parasitoids is determined by the U.S. Department of Agriculture’s Animal Plant Health Inspection Service facility and depends on how active other states are in biocontrol. Sites typically receive 6,000 to 10,000 wasps throughout the summer.

The parasitoid wasps are produced at a specialized rearing facility in Brighton, Mich. These wasps use emerald ash borer to complete their life cycle.

The MDA has released wasps since 2010, and has recovered the insects in subsequent years. This means the wasps are finding emerald ash borer and using them to reproduce.

The wasps released by the MDA are:

Oobius agrili - Adult females search ash bark crevices to find emerald ash borer eggs. A female will insert one of her eggs into an emerald ash borer egg. The wasps develop in the emerald ash borer eggs then emerge as an adult.

Tetrastichus planipennisi - Adult females locate emerald ash borer larvae under ash bark and insert eggs into emerald ash borer larva. Parasitized emerald ash borer larva remain active for approximately one week while the parasitoids develop within and eventually consume the emerald ash borer larvae.

Spathius galinae - Adult females locate emerald ash borer larvae under ash bark, paralyze and lay eggs on the outside of the emerald ash borer larva. Parasitoid larvae develop and consume the emerald ash borer larva.

Blackhawk Park was chosen for its size, number of ash trees, and presence of emerald ash borer. Ash trees are abundant in the wooded areas of the park. The western edge of the park where trees are showing signs of emerald ash borer is steep sloped and densely wooded so there are no other practical options for emerald ash borer management as it is not feasible to remove all of the trees. Blackhawk Park is also large enough to allow the parasitoids to disperse and follow emerald ash borer populations.

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