Updates on emerald ash borer treatments
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.
24C Registration of Merit to allows treatment of more trees per acre for emerald ash borer
The original label for Merit 2F allows for up to five 24-inch dbh trees or ten 12-inch dbh trees to be treated per acre with a basal soil drench of basal soil injection. In some cases in Michigan, homeowners or businesses have more than ten 12-inch dbh ash trees per acre. The 24C allows the use up to 0.8 lb ai/A. This will allow tree care professionals to treat more trees per acre.
Soil drenchs or soil injection for emerald ash borer
Soil drenches or soil injections of imidacloprid (Merit and Bayer Tree and Shrub Insect Control) for emerald ash borer should be made at the base of the trunk, not out to the drip-line. The label for Merit instructs arborists to make soil injections for emerald ash borer within two feet of the tree trunk, and the label for Bayer Tree and Shrub Insect Control tells homeowners to drench in a ring around the base of the tree. Our research tests support the use of imidacloprid basal injections or drenches to save ash trees from emerald borer. However, I have now seen several sites where ash trees treated for three years with soil injections of Merit are now dying. In every case, the soil injections were made out to the drip-line of the tree instead of at the base of the tree. If you are using an imidacloprid drench or soil injection, make sure it is done at the base of the tree. Drenches and soil injections will still be effective if they are done in late May or early June.