Hemlock Woolly Adelgid Infestations Killing Trees in Southwestern, PA

Hemlock Woolly Adelgid Ain't no Joke!

Are you seeing fuzzy white spots on your hemlock tree around the underside of the needles? If so, this is a telltale sign of hemlock woolly adelgid or HWA for short. The HWA is an aphid-like insect that can be found in numerous states and we deal with it regularly in Somerset, PA.

Hemlock woolly adelgid infestations can kill a tree within 4 years time. So, it’s a good idea to have an experienced arborist look at your trees if you suspect a HWA problem. They will be able to make a positive identification and move forward with the best treatment option for your situation.

How it Happens

Emerald ash borers damage your trees by laying dozens of tiny (1.2 mm) eggs on the bark. After a few weeks the larvae will hatch and begin burrowing into the wood. Over the next year or two, they will chew through the wood in an S-shaped pattern and eventually emerge as an adult. Those D-shaped holes are caused by the mature beetles tunneling out of your tree. The holes the adults leave behind are only about ⅛” wide, but the S-shaped patterns the larvae create in the bark, known as “galleries”, are much wider.

Other Signs of Emerald Ash Borer Damage

Woodpeckers on or around your ash trees are another red flag that you’re dealing with an EAB infestation. They absolutely love gobbling up these invasive pests. Additionally, “chewing damage on foliage edges” also indicates their presence.

Can I Save My Tree if an EAB Infestation Already Started?

While these pests are killing tens of millions of ash trees across North America, it is possible for your trees to bounce back from this. However, it is extremely important that you respond to the issue ASAP in order to give your trees a fighting chance. Thankfully, a qualified arborist can often provide the EAB treatment option that makes sense for your situation.

3 Common EAB Treatment Options

Trunk Injections

An EAB trunk injection is the most successful method of EAB treatment available. Here’s an explanation of the process from STS Arborists’ Tim Hinebaugh:

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"We drill a small hole through the bark and into the sapwood of the tree. We then insert a one way valve that seals up the hole. Next, we inject the treatment with an IV system. It is fairly low pressure (about 30 pounds like a tire). The tree takes the pesticide which makes it toxic to the bugs. Then you pull out the needle but leave the plug which grows over in a few years."

Please note, this is a treatment that will need to be repeated from time to time to keep your tree free from EAB infestation. Tim notes that the treatment will “last a minimum of 2 years, but you may be able to get 3 years between treatments.” However, EAB trunk injections may not be needed indefinitely throughout your tree’s life.

This is because “when the bugs are thoroughly integrated into our environment, natural predators” will help to keep their numbers in check. These predators include woodpeckers, parasites, and diseases. This isn’t to say that Emerald Ash Borers aren’t still a huge problem around Somerset, PA and the rest of the country. They are. It’s just that it isn’t the same problem it was six years ago.

Emerald Ash Borer
True, emerald ash borers look pretty interesting. But they'll destroy your trees.
Image: Sam Droege, Public domain, via Wikimedia Commons

Soil Injections

Some arborists will offer EAB soil injections as opposed to trunk injections. However, soil injections do not have as good of a result. Therefore, we stick exclusively to offering trunk injections. When we do a trunk injection, we use a product called TREE-äge® (which sounds like “triage”) to address the problem. The active ingredient in TREE-äge® is Emamectin Benzoate, which is “really effective against the EAB.”

Unfortunately, if your tree is too far gone for an EAB trunk injection, there is really only one treatment option left.

Removal… Which Isn’t Really “Treatment”

Sometimes a tree just needs to be taken down. If you aren’t interested in having emerald ash borer treatment done every 2-3 years, then you’ll want to get the tree removed. The longer it stays in place with an infestation, the more unstable it becomes. Eventually, the tree will be so far gone that it won’t be healthy enough for a tree care professional to climb. This will greatly increase the cost to remove it.

Have Your Trees Ever Been Infested With EAB?

If so, let us know what your experience was like by leaving a comment below. We would love to hear from you or answer any questions you have!

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