Help Maine biologists track forest pests into the New Year and beyond
Hemlock woolly adelgid is visible on the undersides of hemlock twigs in winter. (Photo courtesy Maine Department of Agriculture, Conservation and Forestry)
Hemlock woolly adelgid is visible on the undersides of hemlock twigs in winter. (Photo courtesy Maine Department of Agriculture, Conservation and Forestry)
“Many find moments to get outside this time of year. Whether it is on first-day hikes, during Christmas Bird Counts (some take place in January!), taking in some winter sun, mitigating holiday indulgences, or kicking off a New Year’s resolution. Maine Department of Agriculture, Conservation and Forestry and our partners concerned about forest health ask that you take some time to familiarize yourself with some forest pests at risk of spreading to new areas,” said DACF, in a news release.
While you are out, look for their signs. If you think you’ve spotted one, snap a picture and record your location. Then let DACF know at foresthealth@maine.gov or online at www.maine.gov/foresthealth.
Here are two pests that are spreading in Maine.
“We would really like your help tracking them,” said DACF. “Their signs are particularly visible in the winter months.”
Emerald Ash Borer
Winter is an ideal time to look for signs of emerald ash borer, an insect that kills ash trees (Fraxinus spp.). Hungry woodpeckers go after overwintering larvae of this beetle, removing the bark from ash trees as they do. On ash trees, look for shallow excavation by the birds, bright spots on the trunks where the bark has been removed and tracks under the bark created by the immature emerald ash borer. Sometimes you can find the larvae, off-white, flattened, legless “grubs” with a tan head and two dark spines at the rear. When there is snow, the contrasting dark bark scattered around attacked trees can be the first clue to emerald ash borer presence.
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Bright spots on ash bark related to woodpecker feeding (top) and larval tracks revealed beneath the bark (bottom).
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Emerald ash borer larva with tan on head (left side of larva) and two dark spines at rear (right side of larva) (source MN Dept. Ag.).
Emerald ash borer has been found in parts of York, Oxford, Cumberland, Androscoggin, Kennebec, Penobscot and Aroostook Counties. It was most recently found in Hermon in December, 2023. To help people respond to this pest, we would like to know when it is found in new areas (areas outside of the red on the map below).
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Maine DACF would like to know if you find emerald ash borer outside the areas in red on the map above (3 mile buffers on detections).
Learn more about emerald ash borer, caring for ash trees, and regulations and recommendations for use and disposal of ash material on our website.
Hemlock Woolly Adelgid
During the winter months, hemlock woolly adelgid must be attached to hemlock trees in order to survive. Because of that, there is very low risk of spreading it this time of year. Also at this time, the insect feeds when conditions are right, and the white waxy tendrils covering its body lengthen. This bright white “wool” makes a sharp contrast to dark hemlock twigs and needles in the low-angled light of winter, making it a terrific time to scout for hemlock woolly adelgid.
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Hemlock woolly adelgid is visible on the undersides of hemlock twigs in winter.
Recent high populations and mild winters have allowed this insect to make inroads into new areas of the state. Hemlock woolly adelgid has been found in parts of York, Cumberland, Sagadahoc, Lincoln, Kennebec, Knox, Waldo and Hancock Counties. When you get outside this winter, help us find it in more locations by looking at the undersides of hemlock twigs, those attached to the tree and those that have recently fallen to the ground for the tell-tale white balls. December’s epic windstorm brought many small and large hemlock branches to the ground, which makes now an opportune time to look for this pest.
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Towns in Maine with detections of hemlock woolly adelgid in the forest.
Cold winter temperatures limit where hemlock woolly adelgid can thrive. Winter temperatures throughout plant hardiness zones 5a to 6b in Maine (USDA ARS Map below) are expected to be warm enough, frequently enough, to allow detectable populations of this pest to build. This recently updated map shows that many additional areas of Maine are now vulnerable to hemlock woolly adelgid establishment compared to 20 years ago when the pest was first found in Maine.
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2023 USDA Plant Hardiness Zone Map Maine (Image Source, USDA ARS). Hemlock woolly adelgid populations can build to detectable levels in plant hardiness zone 5a and warmer.
Healthy forests are essential to Maine's way of life. When you get outside in Maine, help us keep tabs on the forest. Share our newsletters with friends and coworkers, and get them involved, too.
If you think you've spotted a forest pest of concern:
- Snap a picture (you can also gather a sample if is safe to do so),
- Note the location and
- Reach out! You can use our report form or send us an email.
