It’s National Invasive Species Awareness Week! Help us celebrate by reading on to learn more about invasives threats and what you can do right now to prevent and manage invasives species, courtesy of the State of Maine’s Department of Agriculture, Conservation, and Forestry.

  Invasive Threats to Maine

Of Maine’s nearly 6,000 lakes, fewer than one percent, fortunately, are known to be currently infested with invasive aquatic plants. These plants can hijack the habitat of native fisheries, flora, and fauna; degrade water quality; diminish property values, and reduce water recreation opportunities, including fishing, boating, and swimming. Eleven invasive aquatic plants are identified in Maine law as illegal to import, sell, and transport, with six already discovered in some of Maine’s lakes. DEP and DIFW spend more than $1 million annually fighting these invasive plants.

Invasive terrestrial plants threaten Maine’s wild places and can harm working forests and productive farms. Plants such as glossy buckthorn steadily invade high-quality forests, crowd out native trees, shrubs, and wildflowers, and out-compete the next generation of trees. Along rivers and streams, Japanese knotweed forms dense stands that prevent colonization by native plants. Knotweed roots and shoots are carried downstream in floodwaters, spreading the problem to new locations. Maine prohibits the sale of thirty-three species of invasive plants, and over 100 species are listed on an Advisory List of invasive plants to help guide land managers. The Maine Natural Areas Program (MNAP) within DACF tracks invasive plant distribution and management using the online mapping tool iMapInvasives and encourages Mainers to work with their town conservation commission, local land trust, or garden club to spread the word about invasive plants and work together to remove them.  For more information, visit the MNAP website or

Woodpecker blonding on ash trees, courtesy Jim Tresouthick, Village of Homewood,

Tree of heaven, courtesy Maine Department of Agriculture, Conservation and Forestry.

Maine’s forest trees are under attack from multiple invasive forest insect pests, and the threat of new pests invading Maine is constant. Invasive insects such as emerald ash borer and hemlock woolly adelgid will forever change Maine’s forests as they spread and continue to kill trees throughout the state, while other invasive pests like browntail moth affect quality of life and human health. Other invasive insects like Asian longhorned beetle or diseases like oak wilt have similar potential to damage Maine’s forests if they arrive here. The Maine Forest Service has a strict out-of-state firewood ban to prevent devastating introductions like these and natural resource managers everywhere continue to encourage the use of local or heat treated firewood only. At DACF, the divisions of Forest Health & Monitoring and Animal and Plant Health, working together as Maine Bug Watch, continue to monitor and control invasive insects and diseases whenever possible.

The illegal stocking of species like northern pike, black crappie, or largemouth bass can have the most significant and obvious impacts to Maine’s native fisheries, but sometimes the release of new fish species can occur for other reasons.  Often these illegal acts are intentional, like when someone wants a certain species of sport fish in a lake close to their home. Unintentional introductions can happen as a result of negligence related to threats found in an angler’s bait bucket.  While the level of threat from this type of introduction may be less than that from the intentional establishment of large predatory species, impacts to native fish populations can occur.  DIFW already limits the fish species that can legally be used as bait and prohibits the unauthorized importation of baitfish from outside the state as two strategies to reduce risk, but recently a third strategy was employed to increase awareness related to using live fish as bait.  In January of 2020, DIFW changed fishing regulations in northern Maine to prohibit the use of live fish as bait under the general law and only allow fishing with live bait fish on certain waters (which are specifically listed in Maine’s Open Water and Ice Fishing Laws). This change reinforces the importance of this region’s abundant native and wild fishery resources and stresses the potential damage to those fisheries when baitfish are introduced where they don’t belong.

Emerald ash borer, courtesy Maine Department of Agriculture, Conservation and Forestry.

Top Five Actions Everyone Can Take Right Now to Prevent and Manage Invasive Species

Look for woodpecker blonding on ash trees. This shallow flecking of the bark by woodpeckers is a common sign of an emerald ash borer (EAB) infested ash tree. When you think you see blonding, take the best quality photo (phone pictures are okay), note your location, and report the findings on our EAB Report Form.

Learn how to identify invasive plants that might be growing on your property. For help recognizing problem plants, consider ordering a copy of the Maine Natural Areas Program’s Maine Invasive Plant Field Guide. The guide has detailed photos and recommended control methods to help to reclaim the landscape. Another great way to increase invasive plant awareness is to volunteer with a local land trust or a conservation commission, to help remove invasive plants on local public lands.

Be on the lookout for the invasive tree of heaven, which is host to a new invasive insect threat, the spotted lanternfly. If you think you have seen tree of heaven in Maine, please report it to

Clip those winter webs. For those of us in browntail moth territory, right now is a great time to clip out webs of overwintering browntail moth caterpillars before they become active. Learn more.

Don’t release aquarium fish and plants, live bait, or other exotic animals into the wild. Research before buying an exotic pet and commit to its care; learn more at And remember, it is illegal to import any freshwater fish into the state of Maine without a permit from the Maine Department of Inland Fisheries and Wildlife.

For more information on all the Maine NISAW events, go to

For more information about nationwide NISAW activities visit

For more information about Maine natural resource agency invasive species programs visit