Biological Control of Emerald Ash Borer

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The goal of biological control is to introduce natural enemies from the emerald ash borer’s (EAB) native range to reduce pest populations. Ideally, biological control becomes self-sustaining once these natural enemy populations are established. Eradicating EAB is not feasible, so the goal is to reduce environmental damage below an acceptable threshold. 

Parasitoid Wasps Used in Minnesota

Three species of parasitoid wasps are released in Minnesota: 

• Two species attack EAB larvae beneath the bark of ash trees.
• The third species targets and kills EAB eggs found in bark crevices. 

These wasps are very small, about the size of gnats, and do not harm humans. 

They were selected by the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) and the Forest Service. The wasps were extensively tested to ensure they do not negatively impact other species or the environment. 

APHIS rears these biological control agents at a specialized facility in Brighton, Michigan, and provides them to states with EAB infestations.  

Map of Release Efforts

View larger map of emerald ash borer biological control efforts in Minnesota, including release and recovery locations.