Myriophyllum (water milfoil) is a genus of about 69 species of freshwater aquatic plants, with a cosmopolitan distribution.

[1] These submersed aquatic plants are perhaps most commonly recognized for having elongate stems with air canals and whorled leaves that are finely, pinnately divided, but there are many exceptions.

Three species (M. aquaticum, M. heterophyllum and M. spicatum) have aggressively invaded lakes, natural waterways and irrigation canals in North America.

The widespread invasive Eurasian water milfoil (M. spicatum) is often controlled with herbicide containing diquat dibromide.

Mechanical management can include the use of a long-reach lake rake or aquatic weed razor blade tool.

In 2007, Professor Sallie Sheldon of Middlebury College reported that an aquatic weevil (Euhrychiopsis lecontei), which eats nothing but milfoil, was an effective weapon against it.