July 19 – 25, 2019Vol. 21, No. 7

The Issue of Forest Pests

The caterpillar of the browntail moth has two distinctive reddish orange dots on its back.

by Dale Finseth

Hopefully we can help people at the park or in their back yards identify some invasive forest pests. Maine's Soil & Water Conservation Districts have a project with the Maine Forest Service to help people identify invasive forest pests, i.e. bugs that could do serious damage to our woodlands or in some cases cause you illness. While some of them have not yet appeared in Maine, many have. We need to be vigilant and identify them should they appear.

The browntail moth is already here and seems to be getting the most press coverage right now. Some areas of the State are affected more than others. Many people are experiencing the rash on their skin and other problems. Kennebec County and the midcoast areas seem much more heavily infested. Efforts to, not only identify its spread, but manage and minimize damage are in process.

This moths' caterpillar has two distinct red/orange dots on its back. Its "tents" are also distinctive. They appear at the end of branches rather than closer to the trunk in crotches of the branches. Oak trees and fruit trees seem the more likely targets.

The browntail moth caterpillar has tiny (0.15 mm) poisonous hairs (setae) that cause dermatitis (skin rash) similar to poison ivy on sensitive individuals. Direct contact with the caterpillar or indirect contact with airborne hairs may cause the reaction. Most people affected by the hairs develop a localized rash lasting a few hours or several days but on some individuals the rash can be severe and last for weeks. We have begun to hear much more of this problem. It is also possible for respiratory problems to develop which require a physician visit and possible treatment. This year there is some benefit to the wet weather with the collapse of browntail moth due to the fungus entomophaga aulicae and possibly other pathogens. It is unclear how much that may help now or in the future. But it seems to be shrinking the caterpillar population this year.

Another forest pest already here is hemlock woolly adelgid. It is not that uncommon. We have been working to identify its location, possible spread and efforts to control damage. Evidence of its existence are "woolly' collections on the underside of hemlock branches along the stems where the needles occur. It only occurs on hemlock trees.

While emerald ash borers are little more than half as wide as a penny, these shiny green insects can decimate a forest or woodlot.

Up until two years ago we had not officially seen the emerald ash borer. Well it is now officially identified in Maine, particularly at our southwest border with New Hampshire and also in Northern Maine. The point now is to identify it early and try and limit its spread. The emerald ash borer can devastate woodlots of ash trees.

Once fully established, destroying the wood is often the best option. There are areas in Michigan and New York that have needed to remove all their ash trees. The small shiny green insects bore into the ash trees and destroy the tree from the inside. Sick ash trees should become suspect. The insects are tiny, and the actual holes in the tree's bark are also very small. The damage to the ash tree is the best way to begin identification.

What can a person do? Try and learn how to identify some of these nasty Forest Pests. The Maine Forest Service of the Maine Dept. of Agriculture, Conservation and Forestry has an excellent website for all invasives, including these forest pests.

If you think you have identified one of these critters, do not be afraid to call the Maine Forest Service at 287-3891. They would rather help you learn it is NOT an invasive than have you fail to report the real deal. Take a picture or collect the bug in a bag or bottle and keep it in the freezer. Help out in this effort to protect Maine from these invasives.

Remember, protecting the woods is one way to protect water quality. Do your part!

An earlier version of this article was published in July 2017.