A predominant pest of the ash tree, the emerald ash borer (EAB) is a destructive winged insect native to Asia. The EAB is a bright, iridescent-green to copper-green in color, with a slender body with the widest part behind the head. The EAB measures approximately 1/2 inch in length. This beetle is extremely dangerous to ash trees, having killed millions of ash trees, approximately 870 million alone just in the state of Minnesota.
Brand names for imidacloprid include IMA-jet, Pointer, Merit and Imicide. Imidacloprid is injected into the soil surrounding the ash tree or directly into the trunk. According to the University of Illinois, imidacloprid is proven to be the best against the EAB. Injections need to be applied into the soil within 2 feet of the tree trunk and take approximately one to two months to saturate the entire tree. Trunk injections take less time to move up through the tree -- about two weeks -- and are applied in the spring. Imidacloprid injections tested higher for control of larvae than adult beetles.
Bidrin or injecticide-B moves more quickly throughout the tree when applied through trunk injections. Studies at Michigan State University determined that bidrin was effective for more than four weeks after injection for the control of adult EAB. Bidrin doesn’t appear to be as effective against the larvae and it is toxic to birds, other organisms and humans.
Bifenthrin, brand name Onyx, is a bark and foliage spray. Other foliage and bark sprays include cyfluthrin, bifenthrin, carbaryl and permethrin. These sprays need to be applied in mid May and again in mid to late June. These insecticides have been used to control both the hatching larvae and adult EAB.
Bayer Advanced Garden Tree and Shrub Insect Control contains imidacloprid and is available to the homeowner for do-it-yourself applications. Always read and follow label directions. Insecticides may potentially drift to other areas and sometimes need equipment specially designed for application, so it may be advisable to consult with or hire a professional to treat your ash trees against the EAB.