The emerald ash borer (EAB) is an invasive beetle that is decimating the ash trees of North America. It is the larval stage that does the damage. The grubs excavate galleries, as seen here, through the vascular area of the tree. This is where nutrients are transported up from the roots and down from the canopy, which is why the first signs of damage occur in the foliage.
Other signs of EAB presence are D-shaped holes in the trunk and woodpecker presence. The woodpeckers can sense the grubs under the bark and chip their way in to feed on them. This generally indicates a heavy infestation so the damage done by the beetle larvae is worse on the tree than the woodpecker feeding.
There is an injection treatment available for emerald ash borer, but we always caution its use. There are definitely scenarios where it works, but we don't want to mislead anyone. The cost varies with tree size but it is expensive. Research shows that it helps for 1-2 years on trees with less than 25% dieback, which is a pretty young infestation. If you have an ash on your property that means a lot to you, this might be a good option for you. The treatment will need to be repeated every other year until emerald ash borer is no longer a threat in the area. Alternatively, we're always happy to chat about replacement plantings utilizing other tree species.
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