Alligator weed is a non-native perennial, sprawling, floating plant with hollow stems often in a dense tangled mass, rooted in waters up to 8 feet deep. They also grow from the shoreline, and occasionally free-floating. Its fleshy stems grow horizontally and can reach a length of 30 feet. The leaves are opposite in pairs or whorls with a distinct midrib and range in size from 1 to 3 inches. Alligator weed flowers appear in early spring. It has no petals but five white or colorless sepals up to ¼ inches long. Alligator weed plants growing in aquatic habitats tend to have stems that are hollow and larger than those of plants growing on land. Alligator weed grows throughout the Southeast Region, Texas, California, and parts of the Midwest. Dense mats of alligator weed displace native aquatic and shoreline vegetation and also alter aquatic systems by decreasing water flow, increasing sediment, shading submerged plants reducing oxygen levels, filling in and choking open water habitats. Alligator weed mats provide a breeding ground for mosquitos.
Alligator weed is a pest in aquatic environments and it is prohibited in many states. These plants reproduce mainly through fragmentation and root buds and can be transported by animals, boats, trailers and other equipment. When using water facilities such as ponds, lakes, rivers; make sure all clothing, boats, trailers, and any related equipment are free of plant material prior to leaving. Clean and flush watercraft to rid them of any plant contaminants. Early detection and eradication are highly recommended to avoid infestations. Nutrient availability in the sediment will feed its growth.
Mowing, raking or harvesting can provide short-term control. Hand removal when roots are included has been successful in controlling alligator weed in small areas. All plant remnants must be removed from the area and properly discarded to prevent re-growth. Physical removal along with chemical control and a reduction of nutrients entering the pond will maximize success.
When used carefully according to the label instruction, aquatic herbicides can be safe and effective management tools. The active products that have been successful in controlling water alligator weed are Shore Klear and Sonar AS and Sonar RTU. A nonionic surfactant Cygnet Plus should be mixed in solution with herbicides when plants are treated.
Shore-Klear is a systemic herbicide that will translocate down into the root systems killing the plant. Successful weed management in heavily infested areas can take several years and sometimes annual maintenance spot treatments.
Sonar A.S. is a long-acting systemic herbicide ideal for water bodies with minimal flow. Simply mix Sonar A.S. with water and spray throughout the surface of the water or pour in different spots around the pond. Sonar A.S. does not have water use restrictions.
Sonar RTU is a long-acting, systemic, easy to use herbicide. Sonar RTU does not require mixing, simply open the bottle and treat from the shoreline.
Cygnet Plus is a nonionic wetting agent, sticker, activator, and penetrant all in one. Cygnet Plus increases the effectiveness of herbicides uptake into the plant tissue.