4 Invasive Species to Watch Out for in Maryland

As winter’s chill starts to loosen its hold, they’ll soon be creeping up the side of your house. Burrowing into your neighborhood trees. Overtaking the rivers where you fish and frolic on summer days.

Invasive flora and fauna are everywhere, thanks to our globally connected society. And it’s not just ones from foreign countries—a rogue bug or a herd of feral swine from one state might wreak havoc in another.

University of Maryland College of Agriculture and Natural Resources experts are working to track and stop their spread. Department of Agricultural and Natural Resources Associate Professor Becky Epanchin-Niell analyzes their bioeconomic impacts and optimizes management approaches, while Department of Environmental Science and Technology Professor and Extension Specialist Andrew Baldwin focuses on wetland ecology and restoration.

Now, during National Invasive Species week, they highlight four of the top threats in the state—and ways you can help identify new ones and contain them.

Emerald Ash Borer
This metallic green menace was first introduced near Detroit in the early 2000s, likely from packaging material on container ships from Asia. The beetle larvae bore and feed through the living tree layers below the bark, eventually cutting off the flow of water and nutrients between leaves and roots. An infestation is hard to detect until it’s too late, said Epanchin-Niell. The pest is “likely to cause the functional extinction of ash across the East Coast.”

Ash trees are prevalent in Maryland forests, including many forested wetlands, and were commonly used in landscaping as well as for hardwood flooring and cabinets. Though individual trees can be treated with insecticides, there’s no effective way to protect an entire forest.

There are also major ecological impacts; dead trees can no longer hold back water, so this increases sediment and nutrient runoff into waterways. In addition, the loss of tree canopy has transformed tidal areas in the upper Chesapeake Bay into marshes. To restore the forest in these areas, Baldwin has tested out planting different trees, and he’s also collaborated with photographers and journalists on “The Ash Forest Project” documenting the destruction.

Blue Catfish
Growing up to 100 pounds, these trophy fish were brought to Virginia from elsewhere in the U.S. for game fishing in the 1970s, but they spread beyond freshwater creeks because of their surprising salt tolerance. These massive omnivores, originally from the Mississippi, Missouri and Ohio river basins, are “voracious predators who eat pretty much anything,” said Epanchin-Niell. Today, up to 70% of the biomass (the total quantity of organisms) in some Chesapeake Bay waterways is made up of these catfish, and they’re even a threat to the state’s iconic blue crab.

What’s the solution? Eat them. You might have done so already: UMD’s Dining Services uses the mild-flavored fish on its menus, serving 17% of the Bay’s harvest in 2024. “We want to increase demand for blue catfish,” she says, such as developing new recipes and increasing marketing to make it a more commercially viable product, while also preventing its spread to new waterways.

Common Reed (Phragmites australis)
Used for making thatched roofs in Europe and houses and boats in the Middle East, this sturdy, tall grass, often referred to by its Latin name, Phragmites, has taken over brackish and freshwater marsh communities in the Mid-Atlantic and other parts of North America.

“You’ll see this ocean of grass as you drive up the industrial areas in Baltimore or along the Jersey turnpike,” says Baldwin. While it has displaced native vegetation and could potentially disrupt habitats of animals like turtles, Phragmites may not be all bad; they could help protect against shoreline erosion. “We have to take a balanced look at it, because it’s unrealistic to think we’ll totally get rid of it.”

Vines
Sweet-smelling wisteria might create the perfect spring backdrop for a selfie—but if it escapes into the woods, it can choke out native species. Alongside English ivy and kudzu, these fast-growing vines can keep young trees from growing, and even weigh down mature trees so much that they topple during intense storms. While wisteria and English ivy were originally used for landscaping, the kudzu plant, which can grow up to a foot per day, was purposefully introduced and widely planted to help soil erosion in the wild about a century ago. Today, it blankets parts of the South and can be seen in summertime along roadsides in Maryland, which is at the edge of its suitable habitat.

Dedicated “weed warriors,” including UMD’s own group, can learn to properly identify them and manually remove these vines so they don’t regrow. “This is a good example of citizen engagement,” Epanchin-Niell said. “We as the general public can play our part in so many different ways.”