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NEW ASIAN PEST IDENTIFIED IN SOUTHEASTERN MICHIGAN AS KILLER
OF ASH TREES  EAST
LANSING, Mich. – A tree-boring pest that is killing ash trees
in southeastern Michigan has been identified as the emerald ash borer
(Agrilus planipennis Fairmaire), an Asian pest previously unknown in
the United States.
It
was first discovered this summer by David
Roberts, Michigan State University Extension (MSUE) district agent
and horticultural specialist in southeastern Michigan. The larval stage
of the pest kills both healthy “Ash trees in Michigan and surrounding states have had a number of problems in recent years with diseases such as ash yellows and ash decline, which is brought on by drought, poor growing conditions and secondary pests that kill stressed trees,” McCullough says. “There was a high number of ash trees dying in southeastern Michigan and no one had identified what was causing the high mortality rate until this year.” Beetles emerging from infested sections collected from newly-dead ash trees in June defied identification through the regulatory process of the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) which includes the insect collection at the Smithsonian Institution. It was only after specimens were sent to Bratislava in the Slovak republic that the species was identified as a native of China, Japan, Korea, Mongolia, Taiwan and the Russian Far East. The pest has been found killing ash trees in Macomb, Oakland, Livingston, Washtenaw and Wayne counties. Larvae, which are between 10 and 14 mm in length, are 10-segmented and cream-colored with a small brown head and little pincer-like appendages on the rear end. They feed on the tree’s phloem and outer sapwood, producing S-shaped galleries that look like roadways. Adult beetles chewing their way out of the tree leave distinctive D-shaped exit holes on branches and trunk. The Michigan Department of Agriculture (MDA) has imposed a quarantine to stop ash trees, logs and firewood as well as ash tree nursery stock from leaving Wayne, Oakland, Macomb, Washtenaw or Livingston counties. This exotic pest has a one-year life cycle. Adult beetles are currently laying eggs on the bark of ash trees and will continue through the end of July. The adult beetles are bright green, about 3/8 to 5/8 inch long. The beetle eggs hatch within one to two weeks and larvae will remain under the bark during the winter and pupate next spring. The next generation of adults will likely begin emerging and laying eggs next May. Most infested ash trees with the pest die in two to three years. It is estimated that the pest has been in Michigan for at least five years. “There are more than a dozen other insects that bore into dying ash trees, but this one is different because it infests quite healthy trees as well as stressed trees,” McCullough says. “So far it has only been found in ash trees, but it can apparently kill all species of ash, including green, white and black ash, as well as several horticultural varieties.” The Interagency Invasive Species Task Force -- made up of specialists from MSU, the MDA, the Michigan Department of Natural Resources (DNR), APHIS, the USDA Forest Service and Michigan Technological University -- is gathering what little information there is on the biology of the pest. Task force members have visited sites with infested trees in the Detroit suburbs several times to learn as much as they can, as fast as they can, about the pest, what it’s doing to the trees and how widely distributed it is. MDA personnel have also checked nursery stock and ash trees in parking lots, along roads and in other urban locations. The pest has not yet been found outside of the five-county area. Regulations now being developed to slow the spread of this pest will affect shipments of ash nursery stock, ash logs and other products out of the infested area. McCullough urges all homeowners with ash trees, especially those in the five-county area surrounding Detroit and beyond, to check their trees. She also urges anyone cutting dead ash for firewood not to transport it to other locations for burning. The MSU Diagnostics Laboratory can help homeowners and others identify this and other plant pests. For more information about or identification of the emerald ash borer, contact the MSU Diagnostics Laboratory at 517-355-4536 or the MDA Emerald Ash Borer hotline at 866-325-0023. Contact:
Robin Millsap 517-432-1555, ext. 169, Deb McCullough 517-355-7445, or
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