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A NEW THREAT TO ASH TREES

 

A new tree pest, known as the emerald ash borer, is generating concern among natural resource professionals, entomologists and forest service officials because of the insect's destructive impact on white and green ash trees. Most wood boring insects only target weakened trees, but observations indicate that this insect targets healthy trees as well. This is an alarming find because it suggests that rather than just killing stressed trees in landscapes, the emerald ash borer might be able to attack and kill ash trees in native forests and landscapes.

The emerald ash borer, discovered in southeast Michigan last year is a native of East Asia, including China, Japan, Korea, and eastern Russia. U.S. Department of Agriculture researchers speculate the insect was brought to the United States via infested wooden shipping crates and has been established in Detroit and surrounding suburbs for at least five years. Recently, evidence of the ash borer has been found in northern Ohio. Often trees that lack and evolutionary history with a particular insect or disease are much more vulnerable than are trees that have a long association with the pest. With the ash borer, we've got an exotic insect attacking native trees and it may be that the ash trees don't have a natural defense to protect themselves.

The emerald ash borer often infests a tree for several years, causing the tree to gradually decline and eventually die. A heavy infestation can kill a tree in one season, but a gradual decline over several years is more common. Infestations prove fatal because the larvae feed under the bark, disrupting the tissue that carries nutrients from the roots to the canopy. The insect over-winters under the bark as a worm-like larva. In late spring, larvae pupate into metallic green adults that emerge from the tree at the onset of summer, leaving behind a characteristic small D-shaped emergence hole in the trunk. Adult emerald ash borers also appear to fly to other areas when a host is not readily available, making their spread to new trees that much easier.

Citizens in the area need to be watchful of sudden decline to their ash trees, evidence of the D-shaped exit holes, or the metallic green adult beetles. Citizens who suspect that emerald ash borers may be attacking their trees should contact the Allen County Extension office at 481-6826 (option 3).


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