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Emerald Ash Borer Update

May 21, 2003

The emerald ash borer, Agrilus planipennis, is a new exotic insect pest that was discovered in Michigan and Ontario, Canada, in 2002. The insect has been known to exist in North America for about the last 5 years. It is now present in Toledo, Ohio. Emerald ash borer is a native of China that is suspected to have entered the United States on infested crates or pallets. This wood-boring insect attacks ash trees, including green, white, and black ash.

Emerald ash borer adults are slender, elongate, 1/2-inch-long beetles. They are metallic, coppery green in color. Adults are primarily active from May through July. Adult activity is dependent on weather conditions, as adults tend to rest on tree surfaces during rainy or cloudy weather. Adults consume small quantities of plant leaves during their lifetime. Adult males live about 2 weeks, whereas females may live up to 3 weeks. Adult females lay between 68 and 90 eggs on the bark or inside cracks and crevices of trees from June through July. The eggs hatch in 1 week into flat, white larvae that are 1/9 to 1/5 inch long. They have small, pincerlike appendages on the last abdominal segment. From June through October, the larvae feed within the cambial region of the trunk or branches, including the phloem and sapwood region. They create galleries that are S- or serpentine-shaped and are packed with frass. An infestation results in severe dieback of the upper third of the tree canopy, with the tree potentially dying in 2 years. The emerald ash borer overwinters as a full-grown larva. Adult beetles create D shaped exit holes when they emerge. There appears to be one generation per year in Michigan.

So what is being done? The Michigan Department of Agriculture has placed a quarantine on all ash trees and ash wood products (that is, timber and firewood) in the affected counties to prevent and control the spread of the beetle. Currently, there is an eradication plan, which consists of two phases. The first phase is to cut and destroy every ash tree within a 1/4-mile radius of any visibly infested trees before adults emerge and can fly away. The second phase consists of treating every tree within a 1/4-to 1/2-mile radius from the infestation zone with imidacloprid (Merit, Imicide, Pointer). The goal of the imidacloprid treatments is to kill newly hatched larvae and adults during feeding and maturation.

If you detect this beetle in Illinois, immediately contact the Illinois Department of Agriculture or your local University of Illinois Extension office. Anyone interested in learning more about the emerald ash borer can access the “Emerald Ash Borer Home Page”: www.na.fs.fed.us/spfo/eab/.

Author: Raymond A. Cloyd


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