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Stingless wasps are battling emerald ash borer

The Minnesota Department of Agriculture (MDA) has confirmed that stingless wasps are doing their job in attacking emerald ash borer (EAB).

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Two years after releasing the wasps at Great River Bluffs State Park near Winona, MDA staff has found reproducing wasp populations. This is the first time this wasp species has been recovered in Minnesota.

The wasps are part of a biological control effort to naturally slow the spread of EAB. Since the EAB is not native to North America, it has no known enemies here.

Scientists went to Asia, EAB’s home, and found stingless wasps that feed on and kill ash borer eggs and larvae. The wasps do not attack humans.

MDA staff recently found wasp larvae in trees being sampled for EAB. After being raised to adulthood, the wasps were positively identified by the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) to be the same species initially released in Minnesota to combat EAB.

MDA first released stingless wasps in Great River Bluffs State Park in September 2011. Wasps have also been released in Houston County and the Twin Cities, all areas known to be infested with emerald ash borer.

These biocontrol efforts were funded by the Environment and Natural Resources Trust Fund as recommended by the Legislative Citizens-Commission on Minnesota Resources.

EAB was first discovered in Minnesota in 2009. EAB larvae kill ash trees by tunneling into the wood and feeding on and disrupting the flow of tree nutrients.

To prevent the spread of EAB during the winter months, MDA reminds Minnesotans to buy firewood locally from approved vendors and burn it where they buy it, and to be aware of current quarantine restrictions.

If in a quarantined county, be aware of the special restrictions on movement of products such as ash trees, ash limbs and firewood.