Protect trees against the emerald ash borer

Property owners with healthy, valuable ash trees, are encouraged to treat them with insecticide this spring, to protect against emerald ash borer. The pest is currently the most damaging threat to trees in Wisconsin, killing more than 99 percent of the ash trees it infests.

A common first sign of emerald ash borer infestation, is woodpecker damage created when birds feed on emerald ash borer larvae beneath the bark of ash trees. Treatment of infested ash trees is more likely to succeed if the trees have low or moderate levels of woodpecker damage.

Now is a good time to consider insecticide protection, because the treatments are typically done between mid-April and mid-May.

Emerald ash borer was recently found in Bayfield and Lincoln counties for the first time, and has become so widespread, that treatments are worth considering anywhere in Wisconsin.

The highest risk of infestation is in communities already known to be infested, or within 15 miles of a known infestation.

Homeowners can apply some insecticide products and others must be applied by a certified professional.

Stay informed and be on the lookout for emerald ash borer. Know where the pest has already been found, and look for the signs and symptoms of emerald ash borer infestation.

Ash trees should be inspected for woodpecker damage called “flecking,” where pieces of bark have been removed while feeding on emerald ash borer larvae beneath the bark. It usually starts up in the canopy and progresses down the tree over the next few years, if the tree is not treated.

Sprouts growing from the base or trunk of the tree are also a sign of infestation, as well as a thinning canopy, with smaller, pale leaves.

In addition, small (one-eighth inch), D-shaped exit holes in the bark indicate the borer, along with green beetles crawling on the trunk of ash trees during the summer.

For more information or to find a list of certified professionals, visit emeraldashborer.wi.gov.