IDENTIFICATION — If you have an ash tree (Fraxinus spp.), keep an eye out for emerald ash borer. Native to Asia, this pest is a serious problem in Michigan, Indiana, Ohio and Ontario. Several surrounding states have infestations to a lesser degree.
Emerald ash borers (EAB) are slender with metallic green wing covers. But you don’t have to see the insects to know that they’re there. Adults chew small, 1/8-in.-diameter D-shaped exit holes in the tree in spring. Soon after they emerge, females start laying eggs in the crevices of ash tree bark. Larvae burrow back into the bark to overwinter, pupating into adulthood in early spring.
DAMAGE — Adults feed on leaves and don’t do a lot of damage. It’s the larvae, which feed under the bark, that cause problems. They disrupt the flow of water and nutrients, which eventually girdles and kills the tree. The tree can die within two years of initial symptoms. White, green and black ash trees are equally tasty to EABs. Dieback usually starts in the top third of the canopy and works downward.
CONTROL — New treatment methods provide hope that this pest can be beaten. The new pesticide Tree-age® did very well in 2007, its first year of use. It’s applied every other year by trunk injection and can only be purchased and applied by certified arborists or landscapers. In Canada, a similar treatment, TreeAzin®, is working, too. Predator wasps native to China have been released in Indiana, where results are still pending.
You can help prevent movement of EAB by not transporting firewood or logs from quarantined states to others. For more information check out www.emeraldashborer.info. If you suspect your tree has an infestation, contact your local extension agency to report it.