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Early Signs of Emerald Ash Borer

Posted on Sep 30, 2014

At about the size of a tic-tac, the Emerald Ash Borer (EAB) doesn’t seem like it could possibly do much harm; however, its size allows its invasion to often go undetected. The ash borer is a non-native wood boring beetle that is capable of causing thousands of dollars of damage to ash trees, which make up 10% of New York’s forest and are favorable for planting along street sides in urban centers and towns. With an invader that is so small and with so many trees, how is it possible to detect this unwelcome bug? Knowing the signs and symptoms can help catch this intruder early in the act and increase the chances of successfully treating a victimized tree.

Emerald Ash Borer Bark Cracks

Emerald Ash Borer adults will lay their eggs in the bark of any size ash tree. As the larvae develop and begin to burrow into the soft tissues of the tree (phloem), which are used to transport nutrients throughout the tree, the bark above or below will begin to crack. This opens up the bark and can sometimes make the larvae’s galleries visible.

Emerald Ash Borer Galleries

Underneath the bark cracks, “S” shaped galleries (or pathways) are formed by the larvae eating their way through the phloem of the tree. As the larvae grow larger, the pathways grow wider.

Emerald Ash Borer Woodpeckering and crown die-off

From the outside of the tree, Emerald Ash Borer larvae cannot be seen; however, they can be heard. Once the larvae are detected by a woodpecker, the bird will hammer away, collecting as many juicy EAB larvae as it can. Woodpecker holes all around the tree are a good indicator of EAB’s presence, as well as the resulting crown die-back pictured also.

Canopy die-back

As an EAB infestation continues, noticeable crown die-back will occur. While EAB larvae feed away at the inside of the tree, adult beetles will feed on the leaves, hitting the tree hard both inside and out!

If an ash tree is seen exhibiting these signs or symptoms, or others such as “D” shaped exit holes in the bark or sprouting of new trees on an existing tree’s trunk, then action should be taken to eliminate the pesky Emerald Ash Borer causing all the problems. Trees that are showing these signs have the potential to be treated to rid them of EAB or can be cut down to prevent the possibility of injury from a falling tree or branch as a result of the tree’s death. One important thing to note however, is once a tree is cut it cannot be sold off as firewood. The easiest way to spread EAB into new locations is through the transportation of infested wood.

While Emerald Ash Borer may seem like a scary invasive that has the potential to kill off our local ash trees, we have an opportunity to stop it in it’s tracks. Simply knowing the signs and symptoms of an EAB infestation can aid in identifying trees in need of help. Furthermore, reporting potential EAB to NYS DEC, Cornell Cooperative Extension or to us here at RTPI can help confirm EAB activity and take action to get it out of our local forests and urban areas.

So this fall keep an eye out for any suspicious activity and join in however you can to help keep this bug out of our backyards!

Elyse Henshaw
Conservation Technician