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Alligatorweed is a perennial aquatic weed commonly found in shallow waterways in Florida and other southern states. It belongs to the pigweed family and is sometimes accidentally introduced to landscape situations with new St. Augustine sod. It can survive on terrestrial sites that remain wet or boggy.
Alligatorweed has 2 to 5 inch oppositely arranged leaves that are elliptic shaped and have a distinct mid-rib. This species has white flowers. Leaves have hollow and very smooth stems. It can go unrecognized in closely mowed St. Augustine turf.
The best control is to inspect sod to make sure the weed is not present. If the weed is present in large enough quantities it can compete for water and nutrients and cause sparse areas in the new turf. Under normal circumstances the weed should die out in 4-8 weeks because soil and moisture conditions in Coastal Georgia are not favorable to alligatorweed. There are no herbicides labeled for alligatorweed control in turfgrass. However if the problem persists for more than 2 months and the turf is well established, Image can be sprayed at maximum rates. Image has good activity on pigweeds, and as alligator weed is in the pigweed family, Image may very well control this weed. Alternatively two-way and three-way herbicides that contain 2,4-D and dicamba may also be used. But, these products can severely injure St. Augustinegrass, and should only be used at the lowest rate recommended on the label for St. Augustinegrass and centipedegrass.