Emerald Ash Borer
A new invasive species, the Emerald Ash Borer (Agrilus planipennis),
has been discovered in the upper Midwest. Previously unknown in North America,
this buprestid beetle was found this summer in southeast Michigan and has been
confirmed in Windsor, Ontario, Canada. Trees in the landscape, in nurseries and
in wooded areas were infested with the borer. Apparently the pest has not spread
beyond the Detroit area, but because of the means of introduction (probably
dunnage from cargo ships) other infestations could exist. Be on the lookout for
this ½-inch long, metallic green beetle that is native to China, Korea, Japan
and other Asian countries.
Infestations of emerald ash borer probably go undetected for years. The first
signs of infestation are tree decline – typically the upper third of a tree will
die back first, followed by the rest the next year – followed by a large
number of shoots or sprouts arising below the dead portions of the trunk. Adult
exit holes and the distinct larval tunnels under the bark are other evidence of
infestation.
The adult beetles emerge in May and June in southern Michigan. They are most
active on warm, sunny days and hid in bark crevices or on foliage during rainy
or cloudy weather. Females deposit eggs on tree bark through July. Eggs hatch
and the larvae bore through the bark into the cambium. The creamy white larvae
feed for several weeks in the phloem and outer sapwood. The winding galleries
they produce as they feed eventually girdle and kill branches and entire trees.
They overwinter as full-grown larvae in a shallow chamber in the sapwood and
pupate in early spring. The adult beetles typically make a D-shaped exit
hole when they emerge.
This wood boring beetle has only been observed on ash trees in Michigan,
although other trees may serve as hosts. The Michigan Department of Agriculture
has placed a quarantine on ash trees and tree parts in those counties where the
pest has been found to prevent further spread.
While it is unlikely emerald ash beetle has invaded Wisconsin, if you see
this beetle next spring or notice trees with signs of damage, report the
information to your local county Extension office. Note
the date and location where you found the beetle or damaged tree. If you can
capture the beetle, place it in a plastic jar and put it in the freezer to kill
it, then take it to your county Extension office.
– Susan Mahr, University of Wisconsin
Photos from
Michigan State Department of Agriculture website
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