The USDA Forest Service, in conjunction with other federal agencies, state and local officials, announced today that Evanston will be the next site in the United States to utilize an alternative method to battle the Emerald Ash Borer (EAB). This aggressive species of tree borer has had a devastating effect on Evanston‘s ash trees, killing about 2,000 trees since 2006.


The USDA Forest Service plans to release one of three tiny parasitic insect species this week in north Evanston and in the City of Chicago to help reduce the destruction of the ash trees. These insects are specialized wasps that search the bark of ash trees for EAB eggs or EAB.  They range in size from a poppy seedsto a sesame seed and do not harm humans or other animals. These parasitic wasps use the eggs or larvae of EAB as food and protection for their own eggs, and consume EAB eggs or larvae before developing to the adult stage.  These are important natural enemies adapted to controlling EAB populations in its native range in China.  


According to the USDA’s Animal Plant Health Inspection Service (APHIS), the EAB is a non-native beetle discovered in southeastern Michigan in 2002. Adult EAB nibble on ash foliage but cause little damage; it is their larvae that cause the devastation. The larvae feed on the inner bark of ash trees, disrupting the tree’s ability to transport water and nutrients, eventually killing the tree.

The EAB arrived in the United States from Asia. Since its discovery, EAB has killed tens of millions of ash trees in southeastern Michigan alone, with tens of millions more lost throughout Illinois, Indiana, Kentucky, Minnesota, Missouri, New York, Ohio, Pennsylvania, Virginia, West Virginia and Wisconsin, as well as in Quebec and Ontario, Canada. To combat the spread of EAB, regulatory agencies and APHIS impose quarantines and levy fines to prevent potentially-infested ash trees, logs, or firewood from moving out of areas where EAB has been discovered. Furthermore, it has cost municipalities, property owners, nursery operators, and forest product industries tens of millions of dollars.

Native species of similar parasitic insects suppress the populations of native wood-boring beetles, such as those that attack oak, apple, and birch. The introduction of EAB natural enemies from Asia to the U.S. will help restore the balance of nature disrupted when EAB became established in our ash trees in the U.S. Physiologically, these EAB natural enemies attack EAB eggs or larva, or possibly other very close relatives, such as the two-lined chestnut borer, raspberry cane borer and bronze birch borer. This is due to the size of the insects, the timing of their development, and their host plants.


For example, Oobius agrili (the species to be released locally) uses the eggs of the EAB in which to lay its eggs.  The eggs of smaller EAB relatives are too small to support the development of this natural enemy. The USDA Forest Service has conducted extensive research on Oobius agrili and has previously released this species at research sites in Michigan, Ohio, Indiana, and Maryland.

“This Emerald Ash Borer biocontrol effort is Evanston‘s chance to be on the leading edge of the research effort to find a way to slow the spread of this destructive pest,” explained Paul D’Agostino, Superintendent of Evanston’s Parks/Forestry Division. “I believe that the potential benefits of this effort far outweigh the risks, based on all the research performed thus far. The potential devastation of the EAB is enormous if we cannot find some way to suppress its populations soon.”

The Evanston Environment Board gave their endorsement of the project last month and the USDA Forest Service has already obtained all necessary permits for the project. This is a joint project between federal, state and City of Evanston agencies which is entirely funded by the federal government.  For further information on EAB, please visit