This is the one time of year when the emerald ash borer (EAB) can be seen, if you have good eyes. The tiny, metallic green adults have emerged from inside infested ash trees, and have taken flight in search of a mate.
Your eyes have to be good to see EAB adults because they are tiny – a mere half inch long – and their goal is to lay eggs way up in the tree tops. This is the time of year to take action to protect your non-infested ash trees and treat any ash tree that may already be infested.
Everyone in the green industry is looking for a way to help you do this and, of course, make a buck. Recently, a story appeared in a local newspaper in which a garden store recommended do-it-yourself treatment using a product containing Imidacloprid for soil drench and a product containing carbaryl to spray in the tree crowns. I am writing this to warn you that you will be wasting your money if you invest in this or any do-it-yourself remedy for this persistent pest. It is a job for tree health care professionals.
Imidacloprid is the only material labeled for consumer use. However, the maximum legal strength for consumer use is so weak that it can only be effective on trees two to three inches in diameter. And, the more is better theory won’t work. Even using commercial strength Imidicloprid as a preventive measure requires annual applications, twice a year to treat an already infested tree.
As for spraying carbaryl, you’ll likely only kill any bees near the spray. EAB adults are looking for love, not food.
The only product I recommend is called TREEage, and is only sold to state licensed applicators who have been trained by the manufacturer in the use of its product and application equipment. The active ingredient in TREEage is Emanmectin Benzoate, and it only has to be applied every two years as a preventative, annually as a treatment.
My conclusions were echoed by a research scientist with the Pennsylvania Department of Natural Resources and other scientists.
Trying to treat this deadly pest yourself is really false economy. You can hire a tree health professional to apply TREEage every two years for a good many years for what it will cost to have a large, dead ash tree removed and replaced after the emerald ash borer kills it.