What to watch for
Knowledge goes a long way toward doing the right thing. Although your trees might be treated, your neighbors' might not. Therefore if you see early signs of emerald ash borer damage in your neighborhood, you should warn your neighbors. It's the right thing to do.
Below are seven signs to watch for. Any one of the seven could be the very first symptom you might recognize.
1. The Presence of an Emerald Ash Borer Beetle
The emerald ash borer (EAB) is a slim, usually iridescent-green beetle with short antennae. They're small and somewhat illusive, which means their presence is a reliable symptom of infection only if you are unlucky enough to spot one. EABs spend most of their life-cycle as larvae chewing on the growth wood under a tree's bark. In Central Iowa the larvae pupate around the first of May. In late May or early June they chew through the bark and emerge as adults from D-shjaped holes. They eat, mate, and lay eggs into August after which they die.
2. D-shaped holes
The EABs metamorphose into an adults while still under the bark of an ash tree. Soon after becoming adults, they chew through the bark and emerge from D-shaped holes that are almost exactly 1/8" wide. If you see D-shaped holes on the trunk of your tree or on its largest branches, you might still be able to save your tree as long as the upper third of the canopy has a normal abundance of leaves.
Woodpeckers on ash trees is a fairly reliable symptom of EAB infection. The woodpeckers are looking for EAB larvae under the bark. Also look for dime-sized divots in the bark where the woodpeckers have pecked holes to get at the larvae. Woodpeckers are often the first symptom a person notices, because several of the other symptoms don't appear until the larvae have had time to girdle the tree and stop its flow of sap.
4. Chewed leaves
Chewed leaves could be the first symptom you see, because the first thing an EAB does when it lands on an ash tree is eat leaves or lay eggs on the trunk. The pattern of chewing is erratic and haphazard. (See adjacent photo.) Trees treated with emamectin benzoate living in an epidemic area sometimes have leaves that have been chewed on by the EAB. In comparison the leaves of untreated trees located in the same area will show a whole lot more damage.
5. Epicormic Shoots
Epicormic shoots are twigs that sprout directly from the trunk or main branches of a tree. They more often go by the name of "water sprouts" or "suckers." On an ash tree they are a sure sign the tree has been injured and continues to be under stress. They usually appear as a symptom during the second year of an EAB attack.
6. Split Bark
The bark of an ash tree often splits when the larvae of boring insects chew tunnels under the bark. The EAB isn't the only culprit. There are many other insect species that bore holes into ash trees. One of the more common ones is the flatheaded appletree borer. Its exit holes are generally D-shaped, and at 3/16" wide they're only slightly larger than the EAB's. However the appletree borer's trails do not zigzag back and forth as much as the EAB's, and an infestation of flatheaded appletree borers is much less lethal to ash trees.
The branch in the photo is from an ash tree. A piece of bark was remove from the branch to expose the trail made by the larva of a flatheaded appletree borer or perhaps a related species. Note how the bark is split just above and to the left of where the bark was removed. This type of split is a classic symptom of an EAB infection.
7. Dying Branches
The three photos to the left are all from the same tree. (If you are viewing this webpage from a smart phone, the three photos are above.) The first sign of dying branches is yellowing leaves in the top 1/3 of a tree's canopy. Not all leaves will turn yellow at the same time. Please compare the dark green leaves in the center of the top photo to the yellowing leaves located in this photo's top right corner. The top and middle photos were taken on May 20, 2014.
If you look closely at the middle photo, you can see some scattered yellowing in the upper 1/3 of the canopy. This tree is is structurally sound, in a park setting, and could live a long time. It's a tree worth treating at this stage of the disease.
The bottom photo was taken on July 26, 2015. If the tree portrayed in this photo were treated immediately, it would have a 50/50 chance of survival, but it would retain some damage that would take several years to recover from. Im most cases a tree like this is not worth saving.
Do you have questions about emerald ash borer symptoms? We offer free advice, free inspections, and free estimates. Give us a call. Drop us a line. We look forward to hearing from you!