Water milfoil depletes the oxygen of a lake, increases sediment and robs other plants of sunlight. Milfoil decreases biodiversity and, while edible, is a poor food source for aquatic wildlife.
Milfoils are aquatic plants that grow beneath the water with roots in the lake sediment. They are common decorative plants in aquariums and backyard ponds, leading to the spread of non-native milfoils. Milfoils spread easily; fragments of a plant break away and sink to take root or float and spread to new areas of the lake. Thick milfoil growth prevents gas circulation in a water body, depriving the deepest parts of the lake of oxygen. It also creates shade that prevents sunlight from reaching slower growing native plants. Thick mats of milfoil trap sediment leading to siltation and changes in water flow and depth. All of this leads to the death of native species, decreasing the diversity of plant life in a waterway. Many waterfowl species feed on milfoil due to its abundance, but it is a poor nutrition source compared to native plants.
Complete removal of invasive milfoil is difficult to impossible depending on the size of the waterway. Selective herbicides, hand pulling, harvesting and dredging are common management solutions. The introduction of grass carp is useful, but the fish must be sterile to prevent them from having a negative impact on the lake as well.