News

State Activates Response to Emerald Ash Borer

The Illinois Department of Agriculture confirmed the arrival of the emerald ash borer (EAB), a pest that burrows under the bark of ash trees, in Kane and Cook Counties this summer. A half-inch long, metallic green beetle, the EAB is believed to have been introduced accidentally to the United States from China about ten years ago. It has since developed a stronghold in the state of Michigan and killed nearly 20 million ash trees across the Midwest.

Ash trees make up about 19 percent of Chicago-area community forests, and about 6 percent of Illinois forests. Some municipalities, however, have as many as 35 percent ash trees. EAB larvae tunnel under the tree's bark, cutting off the flow of water and nutrients. Symptoms of infestation are difficult to spot, such as small D-shaped holes in the bark. Other visual cues include bark splitting and crown dieback, which are also symptoms of common stem and root diseases.

For the past three years, a coalition of local, state, and federal agencies led by The Morton Arboretum (visit their Web site for information on identifying EAB and ash species) prepared to respond to a potential infestation in Illinois. The readiness plan includes surveying ash trees, followed by a quarantine of contaminated sites. In areas where infestations are small and isolated, attempts will be made to eradicate the pest. In parts of Michigan, Indiana, and Ohio, officials used insecticides to kill the beetles and removed infected trees.

Disputes among arborists and state agencies in Michigan, however, raise questions about whether eradication efforts address the problem, or instead cause unnecessary harm to native woodlands. Conservationists in this region worry that large-scale removal of trees in forest preserves could severely damage the healthy understory through trampling by heavy machinery.

"If you start with a healthy tree and apply a chemical treatment [through soil application around the trunk or as an injection in the trunk], the treatment will help," says Rex Bastian, entomologist with The Care of Trees. "But if the tree comes under attack, you still risk losing the tree. The only treatment that is 100 percent effective is to remove the tree."

"We've had success controlling the Asian long-horned beetle in Illinois," says Edith Makra, Community Trees Advocate at The Morton Arboretum, referring to another recent invasion by a tree pest, "but the EAB is an entirely different exotic. We need to investigate the extent of the infestation. There are no plans to cut down trees yet, and we hope that the infested sites can be contained." Makra says the Illinois team will take action based on the severity of the threat, keeping the sustainability of the state's forests a top priority.

Bastian cautions that consumers should purchase firewood from local sources, and not move firewood around the region.

— Divina Baratta