seal  Purdue News

June 3, 2003

New forest pest threatens Hoosier ash trees

WEST LAFAYETTE, Ind.– The emerald ash borer, an invasive insect species that eliminated millions of ash trees in Ohio and Michigan, may be heading for Indiana next.

First identified in the Detroit area last year, emerald ash borers have already killed more than 5 million ash trees, transforming formerly tree-filled neighborhoods into shadeless tracts, said Jodie Ellis, invasive species expert at Purdue University.

Although the emerald ash borer has not yet been detected in Indiana, an infested area in Michigan is located only 50 miles from the state's northeast border.

"It is possible that the emerald ash borer is already in Indiana and that we simply have not detected it yet," said Ellis, invasive species education coordinator for the Department of Entomology. "Ash trees that are infested with emerald ash borer may not show any noticeable symptoms for three years. By the time people become aware of symptoms, it's probably too late to save the tree."

The larval, or immature, form of the insect destroys live ash trees by eating away at the vascular tissue that supplies nutrients to the tree. After the vascular tissue is damaged, the tree starves to death within three years of infestation.

The first warning sign of an infestation is the thinning out of the upper third of the tree's leaves. As beetle larvae cause increasing injury to the tree's vascular system, the tree will try to fight back by sending a large number of sprouts below the damaged portion of the tree trunk.

The adult beetle is slender and colored a bright metallic coppery green. It is only one-third to one-half inch long, making it difficult to spot in tree leaves. Often, small D-shaped holes can be found on the trunk and branches of infested trees, caused by adult borers emerging from under the bark.

Scientists currently know little about how far or how fast emerald ash borer spreads, or even if the pest will ultimately restrict its feeding to ash trees.

"One of the most important things people can do to slow the spread of emerald ash borer is take care not to move firewood and other ash products from infested areas into Indiana," Ellis said.

Homeowners also can help their trees survive a possible emerald ash borer onslaught by watering trees when needed.

"A healthy tree always has a better chance of surviving insect infestations than a weak tree," Ellis said. "It makes good sense to give your ash trees every possible advantage before the insect arrives and the real fight begins."

There is hope on the horizon for homeowners who wish to protect valuable trees from emerald ash borer in the form of Imidicloprid and other injectable insecticides. Imidicloprid has proven successful in protecting against ash borer and other borer-type insects.

Those concerned that their trees may be infested with emerald ash borer should contact a local arborist to get a diagnosis and to discuss prevention and treatment options. Indiana citizens also should contact the Indiana Department of Natural Resources if they suspect that trees in their area are infested with emerald ash borer.

"This is not a trivial problem," Ellis said. "Emerald ash borer has the potential to seriously affect the number of ash trees in our forests and neighborhoods. In the case of emerald ash borer, it's important that everyone be on the lookout for this insect."

Writer: Meggie Issler, (765) 494-8402,

Source: Jodie Ellis, (765) 494-0822,

Ag Communications: (765) 494-2722; Beth Forbes,;

Related Web sites:
Michigan Department of Agriculture
USDA Forest Service

NOTE TO JOURNALISTS: Photographs of emerald ash borers are available at Credits for photos should be given to David Cappaert, Michigan State University.

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