As we enjoy the height of summer, we can also start to see the effects of pests on the leaves and needles of trees.
August is the peak season for invasive insect activity. Here are a few insects you might see in the woods this month, plus two you hopefully won’t.
Browntail moths
The caterpillars that may have given you a painful rash a few months ago have grown up into moths. Many have already mated and laid their eggs on plant leaves. The eggs have a hairlike covering, but they’re different from those on the caterpillars and likely won’t hurt you. Keeping outdoor lights off as much as possible through early August can reduce the number of moths attracted to your home, according to an update from the Maine Forest Service.
Forest tent caterpillars
These caterpillars, which eat through the leaves on aspens trees and sometimes sugar maple and yellow birch, damaged more than 60,000 acres by early July.
Most of that damage has been in northern Aroostook County, plus the state’s western border in Somerset County, according to the forest service. The aspens further north have largely grown leaves again, the service found. Leaf damage reduces the tree’s capacity to produce sugar, a concern for maple syrup producers.
Spruce budworm
These moths have been present in Maine for decades, and their populations typically change in cycles. Maine’s most damaging outbreak ran from 1967 to 1993 and researchers have predicted another will begin in the next few years.
In their caterpillar stage, the native moths can eat and kill spruce and fir trees. The outbreak more than 30 years ago covered 136 million acres across Canada and Maine at its peak, destroying from 20 million to 25 million cords of spruce and fir. Surveys found little to no growth in spruce budworm damage in 2022 and 2023.
If you suspect you have them on your property, you can submit a report to the state.
Emerald ash borer
These invasive green beetles feed under the bark of ash trees as larvae, almost always killing the tree. They were found in Maine six years ago and are mostly found in the southern and far north areas of the state.
As they exit the trees, the borers leave D-shaped holes in the bark. The adults can often be found near the tops of the trees. Maine has a unique collaboration of Wabanaki tribes, researchers and foresters working together to manage the borer’s spread into Maine.
There are also at least two species that haven’t been spotted in the state yet but are worth keeping an eye out for, according to the forest service.
The Asian long-horned beetle
This beetle’s larvae feed and tunnel through the bark of hardwood trees such as ash, birch and maple. As they grow, they’ll eat deeper into the tree and can eventually kill it. Like the emerald ash borer, Asian longhorn beetles can travel in firewood transported from out of state.
The closest confirmed population is in Massachusetts, though there have been some recent false alarms in Maine: the insects look similar to the white-spotted sawyer beetle, a native bug that prefers trees that are already in poor condition.
The elm zigzag sawfly
True to its name, this invasive bug’s larvae eat through elm tree leaves in a zigzag pattern. If there are enough of them, they can take out all the leaves at the top of the tree and make it more susceptible to other diseases.
These also haven’t been found in Maine, but are in neighboring Vermont and Massachusetts.
Because multiple pests and diseases can travel in wood products, the forest service banned transport of firewood into Maine from other states unless it’s been heat treated at 160 degrees Fahrenheit for 75 minutes, with a certificate to prove it.
Some areas of the state are also under quarantine, restricting movement of forest products in an effort to slow the progression of emerald ash borer.
