Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Homeowners have the option of treating ash trees themselves to protect trees from emerald ash borer by using imidacloprid as a basal soil drench. Imidacloprid is available to homeowners at local garden centers as Bayer Advanced Tree and Shrub Insect Control, and more recently as some other products. We have tested the Bayer Advanced product, but not the others.

The imidacloprid product is mixed in a bucket of water at the concentration of 1.0 ounce per inch of trunk circumference. The bucket of solution should be mixed and poured around the base of the trunk in May or early June. Treatments should begin when trees are healthy. Repeat this treatment each year.

The cost of treating an ash tree with a 32-inch circumference is about $22 to $26 per year. Several field trials have been conducted using this treatment method with very good results: greater than 95 percent success for trees with less than a 12-inch trunk diameter (38-inch circumference), and 75-85 percent success for trees with a 12 to 15-inch trunk diameter (dbh). These products are not recommended for trees with a trunk dbh of greater than 15 inches.

Failures to save ash trees with this treatment are most likely to occur with large trees growing in dry soils. More detailed information and pictures are in MSU Extension bulletin E2955: Homeowner Guide to Emerald Ash Borer Treatment. The bulletin can be viewed and downloaded from the www.emeraldashborer.info web site.

Dr. Smitley's work is funded in part by MSU's AgBioResearch.