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Emerald Ash Borer

Learn About the Emerald Ash Borer and Its Effects on Trees

The emerald ash borer, shown here as an adult insect with its wings spread, has caused the death of over 60 million ash trees since its discovery in 2002.

Emerald ash borer larvae, which measure 2 to 3 centimeters in length, burrow their way through the inner layer of the ash tree's bark, impeding its ability to conduct water and nutrients throughout the tree. Starved of water and nutrients, ash trees under attack can die in as little as three years.

Emerald ash borer larvae leave distinctive serpentine-shaped tunnels on the surface of the wood—called “galleries”—just under the bark. These galleries can become visible when the tree’s bark cracks and splits as the infestation grows worse.

When emerald ash borer larvae emerge from the bark as adults in mid to late spring, they leave a small D-shaped exit hole in the bark.

Adult emerald ash borers, members of the metallic wood-boring beetle family, measure only 1/2 inch in length by 1/8 inch wide and are a striking, bright metallic green color. The adult beetles, nibbling only on leaves, are actually not very harmful to trees. It’s their ravenously hungry larvae that cause the destruction as they tunnel through the critically important vascular tissues (inner bark layers) of the tree.

Emerald ash borer traps, hanging on trees near to ash trees, attract the beetle by a combination of color and scent. The beetles become stuck to the traps, which have a sticky surface. These traps are used to monitor potential new locations of the beetles—they are not capable of controlling beetle populations.

Learn more about backyard invasives.

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