Emerald Ash Borer

Background

Agrilus planipennis, more commonly known as emerald ash borer (EAB) is a non-native destructive wood-boring pest of ash trees (Fraxinus spp.). EAB was first discovered in North America in 2002 in Michigan. The borer is native to China and probably arrived to North America on solid wood packing material carried on cargo ships or airplanes. It has killed millions of ash trees in the state of Michigan and has now spread to thirty-five states as well the District of Columbia and five Canadian provinces. All species of ash appear to be susceptible.

In Minnesota, green ash is the species most commonly planted in urban and suburban landscapes and it also occurs naturally in native woodlands. White ash is occasionally planted and occurs naturally in native woodlands. Black ash is a species primarily found in wet areas, such as black ash swamps in northern Minnesota. Site and soil moisture factors do not seem to make much difference in terms of a tree’s susceptibility to EAB. Emerald ash borer adults can fly at least a half mile from the tree when they emerge. However, new infestations are most often created when people transport infested nursery ash trees, logs or firewood into uninfested areas.

Shipments of ash trees and transportation of firewood has been regulated by the state to reduce the spread of EAB. It was first discovered in Minnesota in 2009 and has since spread throughout much of the southern half of the state (Total of 87 counties in Minnesota and 36 counties have EAB infestations-August 2022). Washington County is a designated quarantine area and transportation of ash wood outside of the county is prohibited. Emerald ash borer was first confirmed in Oak Park Heights in July of 2021 near Osgood Ave N.

The City was awarded a grant from the Minnesota Department of Natural Resources to assist with costs related to removal and stump grinding of ash trees and costs related to tree replacement. Click here for the Press Release issued by the City on September 8, 2022 regarding the grant.

Facts about Emerald Ash Borer (EAB):

-EAB only attacks ash trees (Fraxinus spp.)

-EAB prefers to attack stressed ash, but can also attack healthy trees.

-Adult beetles are bright, metallic green ½-inch long with a flattened back.

-Larval stage forms “S”- shaped galleries under bark while feeding.

-Adults exiting trees form 1/8 in. “D”- shaped exit holes in bark.

-Canopy dieback/branch dieback-thinning begins in the top 1/3 of the tree’s canopy and progresses until the tree is bare.

-Splits in the bark may be symptoms of an EAB attack.

-Increased woodpecker activity/damage on trees may be a sign of EAB larvae under the tree’s bark.

-Sprouting of epicormic shoots from the base of the tree.

What Can You Do?

Check your ash trees for signs/symptoms of EAB.

Check the following Minnesota Department of Agriculture link for images showing symptoms of EAB, the insect and photos of the damage caused by EAB: https://www.mda.state.mn.us/eab

If you capture an insect, compare it to photos of EAB and look-alike insects (see the Compare Emerald Ash Borer & Lookalike Insects PDF below).

See the Identify Emerald Ash Borer PDF below to access a checklist to determine if you might have an ash tree with EAB.

Water your ash tree during dry periods – EAB prefers to attack stressed trees.

Contact a licensed tree service with a current City of OPH Tree Workers License and individuals on staff that hold a MN Department of Agriculture Commercial Pesticide Applicators License to have private ash trees treated with an insecticide treatment for valuable landscape trees.