2018 ASHS Annual Conference

South Florida relies on a system of interconnected canals to prevent flooding of the mostly flat topography during severe storms. These canals must be kept free of dense vegetation to ensure that stormwaters can flow unobstructed. Aquatic nuisance species that hinder water movement in canals include crested floatingheart (Nymphoides cristata), fanwort (Cabomba caroliniana) and hygrophila (Hygrophila polysperma). Replicated mesocosm studies conducted in a covered greenhouse in south Florida utilized a single water-column treatment of one of 33 treatments (11 aquatic herbicides alone or in combination with another herbicide, plus an untreated control). After 16 weeks of culture under experimental conditions, mortality of all three species was greatest in mesocosms treated with ProcellaCOR, triclopyr, triclopyr+diquat, penoxsulam, penoxsulam+diquat, penoxsulam+flumioxazin, imazamox+diquat, imazamox+flumioxazin, carfentrazone and carfentrazone+diquat. These results suggest that resource managers in south Florida have a number of chemical tools at their disposal to manage aquatic weeds in canals. These findings are valuable because reliance on a single active ingredient can drive the development of herbicide resistance by selecting for resistant genotypes.