An invasive aquatic plant first identified in southern Maine two years ago is now confirmed across southern and western parts of the state, and officials and local groups are taking steps to keep it from spreading farther.

Swollen bladderwort, which forms dense mats on the water’s surface and can change ecosystems and hinder recreation, has been found on eight Maine waterbodies, including Tilton Pond in Fayette, where it was discovered two years ago and has since worsened, making it harder to swim and boat.

Stephen Smith-Herb of the Basin-David-Tilton Ponds Association said a boater using Tilton Pond’s now-closed public launch was likely to blame for the infestation. Keeping the plant from hurting more waterbodies in Maine will take diligence, he said.

“I would encourage the public to understand and follow Maine law regarding the transportation of invasive plants,” Smith-Herb said, asking boaters to follow state guidance on cleaning watercraft. “Many lakes have courtesy boat inspectors — treat them with respect and follow their guidance.”

Swollen bladderwort, or Utricularia inflata, is a carnivorous free-floating and submerged plant that eats insect larvae and water fleas and is native to the Atlantic Ocean and Gulf of Mexico’s coastal plains. It can be found in water bodies from southern New Jersey to eastern Texas and Oklahoma, said David Madore, deputy commissioner for the Maine Department of Environmental Protection.

Swollen bladderwort has also been identified in all New England states, New York and Washington, according to the Maine DEP.

The species has been documented in Horseshoe Pond in Chesterville; Lake Arrowhead in Limerick and Waterboro; Little Ossipee Lake in Waterboro; Milton Pond and Northeast Pond between Lebanon, Maine and Milton, New Hampshire; Mousam Lake in Acton and Shapleigh; Murdock Lake in Berwick; Pleasant Pond in West Gardiner and Richmond; and Tilton Pond in Fayette.

“The best way to prevent the spread of aquatic invasive species such as swollen bladderwort is to ‘Clean, Drain and Dry’ all watercraft and gear after use,” Madore said, adding that, more specifically, recreationists can help prevent the spread of the plant by removing any plant material or debris from equipment, draining standing water away from other waterbodies and drying equipment in sunlight for three to five days.

The infestation in Tilton Pond was first confirmed in August 2023, DEP officials said. Since then, volunteers from the Basin-David-Tilton Ponds Association have removed over 2,500 pounds of swollen bladderwort and installed floating fragment nets at outflows to prevent downstream spreading into David Pond. Residents were trained in the plant’s identification and further efforts are ongoing in coordination with DEP and the 30 Mile River Watershed Association, a collaboration between towns, land trusts and lake associations in central and western Maine.

Silas Mohlar, the aquatic invasive species coordinator for the 30 Mile group, said the plant was first discovered by a retired botanist and Fayette resident who had just begun volunteering as an aquatic plant surveyor for the ponds association. Mohlar said the findings were brought to 30 Mile and the DEP.

“That’s sort of how it was discovered,” Mohlar said. “Then we went from there with some rapid response survey work that we here at 30 Mile coordinated.”

DEP works with local lake associations like Basin-David-Tilton to manage infestations by hand removal, diver-assisted suction harvesters, benthic barriers and, in rare cases, chemical treatments.

Madore said each infestation is unique and requires specific management techniques. Data on long-term success is limited, as most sites have been under management for only two years, he added.

Madore said while swollen bladderwort does not pose any known risks to drinking water sources, its spread could significantly alter lake ecosystems. Early detection and management are key, DEP said.

“There are several native bladderwort species in Maine, which play an important role in lake ecology,” Madore said. “It’s important to distinguish them from invasive swollen bladderwort when reporting potential sightings.”

While there aren’t many people who frequent Tilton Pond, those who do have noticed the impact of the invasive plant, Mohlar said. Some have complained of clogged electric motors, concerns over pets getting tangled in the plants and difficulty swimming.

“It likes to raft up and sort of create these large mats with not only other swollen bladderwort plants but native bladderworts and just native plants in general,” he said, adding that winds often help large rafts of the plant work their way around the pond, congregating around docks and banks.

Mohlar said 30 Mile has focused on containment as much as it has surveying and removal work, as Tilton Pond is upstream from David, Parker and Lovejoy ponds and Echo Lake.

Containment methods include physical barriers, namely fragmentation nets, which are rarely used in Maine. He said volunteers are working with the town of Fayette to limit boat access by installing jersey barriers and a chain-link gate, limiting recreationists to carry-in watercraft only.

“That was one of the first things we did to reduce the risk of the plant going somewhere else via a fragment on a boat trailer,” Mohlar said.

Swollen bladderwort reproduces through fragmentation, the spread of stem fragments, though the plant can spread via seed since it is a flowering plant, Mohlar said, adding that the plant bloomed heavily this past spring.

That makes early detection and containment even more critical, he said.

To report a suspected infestation, follow steps requested by Maine DEP at www.maine.gov/dep/water/invasives/whatif.html.