Lesser naiad is a non-native, small, branching aquatic annual with coarsely toothed leaves. The flowers are small, occurring in clusters along the leaf axils. Curly pondweed is a non-native submerged aquatic plant with oblong leaves alternately placed on the stem. Leaf margins are wavy and have minute teeth along their entire length. There are no floating leaves, but a spike of terminal flowers rises above the water.

HABITAT:

Lesser naiad is most common in rivers and alkaline lakes. Curly pondweed grows in fresh and brackish streams and ponds. Both species often occur with other non-native invasive species, such as Eurasian water-milfoil (Myriophyllum spicatum).

DISTRIBUTION:

Lesser naiad is native to Europe and Asia. It has been speculated that seeds or plant parts were brought here accidentally on ships. Curly pondweed was introduced from Europe over 150 years ago and its increasing distribution may be due to migrating water birds. Both plants are common throughout the United States and are widely distributed in Ohio.

PROBLEM:

Once established, both lesser naiad and curly pondweed can be aggressive weeds. These plants grow profusely early in the season, often shading out and inhibiting the growth of native plants.

CONTROL:

Mechanical

Manual removal of lesser naiad may prove to be difficult due to the brittle nature of the plant. Avoid fragmenting the plants and remove all stems for effective control.

Chemical

Herbicides such as Cutrine®, Weedtrine®, Aquathol K® and Diquat® can be used to effectively kill curly pondweed and lesser naiad.

Biological

No known biological control methods are currently available.

ADDITIONAL INFORMATION SOURCES:

Borman, S. 1997. A field guild to aquatic plants. Wisconsin Lakes Partnership.

Schmidt, J.C. 1987. How to identify and control water weeds and algae. Applied Biochemists, Inc.