• Zebra mussel (Dreissena polymorpha)
• Quaqqa mussel (Dreissena bugensis)
• Chinese mitten crab (Eriocheir sinensis)
• New Zealand mud snail (Potamopyrgus antipodarum)
• Asian clam (Corbicula fluminea)
• Rusty crayfish (Orconectes rusticus)

Eurasian water milfoil was first found in Connecticut in 1979 and can now be found in over 40 lakes and ponds in Connecticut as well as the Connecticut River. Eurasian water milfoil is a  rooted, annual plant with a tan or reddish stem, submerged leaves are usually in whorls of four around the stem. It spreads through primarily through fragmentation. When Eurasian water milfoil reaches the surface, it can form a dense mat, which interferes with boating, swimming and other recreational activities, and can alter the ecosystem of the lake. These plants also produce a reddish flower that emerges from the water.

Variable leaf milfoil was first discovered in Connecticut in 1936 and can now be found in approximately 30 lakes and ponds in Connecticut. Variable leaf milfoil is a rooted, annual plant with a thick red stem and has submerged leaves that are typically opposite. It spreads through fragmentation. Like Eurasian water milfoil, variable leaf milfoil can form a dense mat, which interferes with boating, swimming and other recreational activities, and can alter the ecosystem of the lake. These plants also produce flowering spikes that can emerge from the water.

Curly leaf pond weed is one of the most common invasive plants in Connecticut. It was first

{An image of pond weed.}

discovered in 1932 and can now found in 40 Lakes and pond in Connecticut as well as the Connecticut and Housatonic Rivers. Curly Leaf Pond Weed has a flattened stem with alternate leaves. The leaves are stalkless and have wavy edges (where it gets its name from). These plants spread via turions (soft, hardened leave). Like the invasive milfoil, curly pond weed can produce large, dense mats that interfere with water activities and can alter the ecosystem of the waterbody. These plants differ from most of the invasive plants in Connecticut, in that they often die back by mid-summer. The turions are dormant until the autumn when the water is cool.

{An image of hydrilla}

photo credit: UCONN IPANE

Hydrilla was first discovered in 1989 and can now be found in two lakes in Connecticut, but is considered extremely aggressive and can outcompete native and invasive species. Hydrilla is a perennial with five whorled leaves which are finely toothed, around the stem. It spreads through fragmentation and tubers that overwinter in the sediment.

Fanwort was first discovered in 1937 and can now be found in more

{An image of fanwort.}

than 30 lakes in Connecticut and in wetlands along the Connecticut River. Fanwort has submerged leaves that are opposite and have petioles, or short stems. They also have a few small oval, floating leaves at the top of the plant just before the white or pickish flower that can emerge from the water. Fanwort spreads primarily through fragmentation.

Water chestnut was first discovered in Connecticut in 1999 and can be found in the following locations: scattered sites along the Connecticut River from Hartford to Lyme, both in the main stem river and in a number of coves (including White Oaks Cove, Keeney Cove, Hamburg Cove) and connected ponds. Water chestnut has also been found in a number of other waters scattered throughout CT including the Mattabesset, Hockanum and Podunk Rivers, small ponds in Eastford, Thompson and West Hartford, Bantam Lake (eradicated, non found in the last several years), Mudge Pond and at the confluence of the Still River and the Housatonic River.

Anglers fishing in the Connecticut River, its tributaries, and elsewhere should be on the lookout for this highly invasive plant. DEEP and other organizations are involved in eradication efforts.

Water chestnut is a rooted, annual aquatic plant with triangular-shaped floating and feather-like submerged leaves. Its sharp, spiny fruits wash ashore and can inflict painful wounds if stepped on. Dense water chestnut growth can make fishing, boating, swimming and other recreational activities nearly impossible. 

If you find this plant, contact Harry Yamalis at 860-424-3034 or harry.yamalis@ct.gov . 

{An image of an invasive plant.}

{A photo of an invasive species.}

Didymo is a microscopic diatom (a type of algae) which during “blooms” (a time when the algae goes through explosive and rapid growth) can form large mats of thick cotton-like material that covers large portions of the stream bottom.  Didymo had proven especially problematic in some of New Zealand’s pristine trout fishing waters.

Didymo has been documented in many of blue ribbon trout streams across North America and has been confirmed in several northeastern states. Transport by angler’s waders is considered to be the major source of transfer.  The only confirmation of Didymo in Connecticut to date has been in the West Branch of the Farmington River.  It was first confirmed in the river during March of 2011.  Didymo has not been documented in any other water in Connecticut.

Since its discovery, academic monitoring of Didymo has shown that “blooms” are contained to a small section of the West Branch Farmington River from approximately the Route 20 crossing in Riverton to the confluence with the Still River (approximately one half mile of stream).  This section of stream has ideal chemical and physical characteristics for Didymo.  Small isolated patches have been documented as far downstream as New Hartford (approximately 8 miles downstream).  Anyone coming in contact with the stream bottom in this area is advised to be extra diligent in cleaning their waders/boots or other equipment that has come in contact with the stream bottom before moving to another location on the river or to a different waterbody (or have a second pair of waders/boots available to wear).

Please follow the advice below to help prevent the spread of Didymo or any other potential aquatic species to new waters.

What you can do to prevent the spread of didymo and many other aquatic organisms:

Before leaving the water:

• CLEAN: your waders, boat, kayak, canoe, tube (especially the soles) including rinsing any sand or mud and removing leaves, plant material, or algae.
• DRAIN: all water from your boat, kayak, or canoe before transporting.

• DRY: anything that comes into contact with water (boats, trailers, anchors, propellers, fishing equipment, clothing, dogs, etc.) for a minimum of one week during hot/dry weather and four weeks during cool/wet weather.

• Wash with hot water (preferably high pressure).
• Dip equipment into 100% vinegar for 20 minutes prior to rinsing.
• Use a 1% salt solution (1oz. per gallon) or soap and hot water (Lysol, boat soap, etc.) for 10 minutes prior to rinsing.
• Freeze for at least 24 hours

Vermont DEC

Biosecurity - New Zealand

US EPA Region 8

{Didymo is a threat to trout streams.}

Aquatic Invasive Species