State releases Chinese wasp to fight ash borer

The Connecticut Agricultural Experiment Station reports that small, stingless, parasitoid wasps were released late last month by Dr. Claire Rutledge in the towns of Prospect and Middlebury for the biocontrol of the emerald ash borer.

This biocontrol release is conducted in cooperation with Juli Gould of the USDA Animal Health Inspection Service under specific guidelines for the release of emerald ash borer parasitoids. The female Tetrastichus planipennisi wasp lays eggs inside the beetle’s larvae where the developing parasitoid larvae kill the ash borer larvae.

The emerald ash borer is responsible for the death and decline of tens of millions of ash trees from the Midwest to New York State and south to Tennessee. Ash makes up about 4% to 15% of Connecticut’s forests and is a common urban tree.

This destructive insect was first detected in Connecticut in the town of Prospect in July 2012 and was subsequently found in eight other towns, all in New Haven County, as part of surveys conducted by Agricultural Experiment Station, the Department of Energy and Environmental Protection (DEEP), and the University of Connecticut Cooperative Extension or from reports by the public.

The other eight towns are Naugatuck, Bethany, Beacon Falls, Waterbury, Cheshire, Oxford, Middlebury, and Hamden. Emerald ash borer has also been identified in Dutchess County, N.Y., Berkshire County, Mass., and Merrimack County, N.H.

“The release of this natural enemy of emerald ash borer is another valuable approach in our efforts to manage and slow the spread of the emerald ash borer” said State Entomologist Kirby C. Stafford III.

Another parasitoid, Oobius agrili, which can kill up to 80% of emerald ash borer eggs laid in the summer, will be released at a later date by Dr. Rutledge.

Each female wasp can parasitize up to 62 emerald ash borer eggs in her lifetime.

So far, these two wasps have been released in 14 of the 19 states where emerald ash borer has been found. The wasps, which are extremely specific to emerald ash borer, were discovered in China, where emerald ash borer originated. They are being reared by the USDA in a laboratory in Brighton, Mich.

In Connecticut, a quarantine has previously been established that regulates the movement of ash logs, ash materials, ash nursery stock, and hardwood firewood from within New Haven County to any area outside of that county. The quarantine currently applies to only that part of the state and mirrors a federal quarantine also imposed on New Haven County.

In addition to the quarantine, regulations are in effect regulating the movement of firewood from out-of-state into Connecticut or within Connecticut. These regulations were put in place to ensure that emerald ash borer and other invasive insects are not carried into Connecticut, or spread throughout New England, through the shipment of firewood.

Detailed information about the quarantine and the firewood regulations can be found at  or .

The emerald ash borer is a regulated plant pest under federal (7 CFR 301.53) and state (CT Gen. Statute Sec. 22-84-5d, e, and f) regulations. For more information about the emerald ash borer,   visit A fact sheet providing guidelines on the treatment of ash trees to protect them from EAB is also available at

A factsheet on the biological control of the emerald ash borer is available at