What does EAB Look Like?
EAB looks different in each of its four life stagesAdult (beetle)
Emerald ash borer adults are very small, metallic green beetles. They are about the size of a cooked grain of rice: only 3/8 - 1/2 inch long and 1/16 inch wide.
Adult emerald ash borers emerge from beneath the bark of ash trees late May through mid-July. They create a D-shaped exit hole as they chew their way out of the tree. The beetles are most active during warm and sunny days. They never wander far from where they exit a tree (less than one mile) in search of a mate. Once they find a mate, the female will lay 60 - 90 eggs, one at a time, in the crevices of ash tree bark. The beetles will feed lightly on ash tree leaves, but do not cause much harm that way. EAB beetles live a total of three to six weeks.Egg
Emerald ash borer eggs are very small (1 mm), difficult to find and are rarely seen. Female beetles deposit them in bark crevices and as larvae hatch from the egg, they immediately chew their way into the tree.Larva (immature EAB)
Emerald ash borer larvae are white and slightly flattened, with a pair of brown pincher-like appendages on the last segment. Their size varies as they feed and grow under the ash tree's bark. Full grown larvae average 1.5 inches in length. They wind back and forth as they feed, creating S-shaped patterns called galleries under the bark. Larvae will feed under the bark for one or two years and can survive in green wood, such as firewood, as long as the bark is attached.Pupa
In autumn, after one or two years of feeding under the bark, larvae will create a chamber for themselves in the tree's sapwood. They stay in this chamber over winter and pupate in the spring, turning into adults. The beetles emerge from the tree, completing the life cycle. The pupae, like the larvae, cannot be seen unless bark is pulled away from the tree.EAB Look-Alikes
There are many metallic green insects that are common in Wisconsin and often mistaken for EAB. For more information on these look-alikes please visit the University of Wisconsin - Madison's emerald ash borer webpage.
(Please note that the six-spotted tiger beetle may have any number of spots, or none at all.)
MI Extension Bulletin about emerald ash borer look-alikes and native borers.
More emerald ash borer look-alikes.
Insects in Wisconsin often confused with emerald ash borer
Insects in Wisconsin that can be confused with EAB.pdf
The EAB life cycle, with pictures and descriptions.
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When EAB adults exit the ash tree they leave behind tiny D-shaped holes (about 1/8 inch).
Fourth instar (full-grown) emerald ash borer larva. 1.5 - 2 inches long.
An adult emerald ash borer is a small metallic green insect, only 1/2 inch long and very narrow. These adult beetles are rarely seen because of their small size and because they are only present for 3 - 6 weeks each year.
An adult emerald ash borer on a U.S. penny
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