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Spring Brings Out The Emerald Ash Borer

Soon, tiny green insects may begin flying around your ash tree(s). That could mean the beginning of the end for the tree(s). Or their decline may already have begun.

These tiny insects are the dreaded emerald ash borers (EAB) in their adult stage. It’s flight is a mating flight to begin the next generation of destruction to stately ash trees. After mating, the adults will die, but not before laying eggs on the nearest ash tree.

Photo: Howard Russell, Michigan State University, Bugwood.org

The adult females will carve small indentations in the tree bark and lay an egg in each indentation. This will continue until she has laid her 60-100 eggs. When the larvae hatch, they immediately begin boring into the tree and start feasting on the phloem (food made through photosynthesis and the vessels that distribute it throughout the tree). The feast continues all through the year and, sometimes into a second year. After pupating inside the tree, they emerge as adults and begin the reproductive process.

The infestation begins high up in the tree and progresses down with successive generations. As a result, it’s difficult for the untrained eye to detect an infestation until dieback begins. Our arborists can climb to the top of the tree and look for the adults’ small “D” shaped exit holes.

If your ash tree(s) are infested, annual treatment may help them survive. If your trees are still healthy, we should apply a preventive treatment immediately and reapply it every two years. Treatment for this small but extremely damaging pest is not a do-it-yourself project. The most effective treatment/preventive is injected directly into the trunk of the tree at a concentration available only to certified pesticide applicators. Trees that have lost no more than a quarter of their crown to the emerald ash borer can be treated with a good prognosis. Those with more damage should be removed.

The cost and the need to repeat the application every year or two may seem like a substantial investment. However, a number of treatment or preventive applications can be made for the cost of removing a large, dead ash tree and replacing it with a new tree. And, this doesn’t even include the aesthetic loss, the loss of value to your property, and possible loss of understory landscaping because of their loss of shade.

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