Fluridone Effects on Fanwort and Water Marigold

Growth chamber studies were conducted to evaluate the effectiveness of the aquatic herbicide fluridone for control of fanwort, and to assess the impact of treatment on the nontarget plant, water marigold. Treatments included static exposures of 0, 5, 7.5, 10, 15, 20, and 30 g fluridone L. Changes in pigment concentrations within the plant (phytoene, β-carotene, and chlorophyll) and biomass were used to appraise treatment efficacy. For fanwort, phytoene levels increased 82% and β-carotene decreased 88% when exposed to 5 g fluridone L for 14 days. Effects on these two pigments persisted through 84 days after treatment (DAT) for fanwort. In contrast, phytoene content was not affected in water marigold however, plants exposed to ≥10 μg fluridone L showed reduced β-carotene 84 DAT. Leaf chlorophyll decreased with increasing fluridone concentration in fanwort whereas in water marigold, decreased chlorophyll was observed in plants treated with rates of 7.5 g L and higher. Despite these observed differences in pigment response, all fluridone treatments significantly reduced shoot dry weight biomass. Overall, the data showed that biomass and pigment levels of water marigold were minimally impacted following treatment of 5 g L fluridone. However, the dose of fluridone required to control fanwort by >80%, severely inhibited water U.S. Army Engineer Research and Development Center, Waterways Experiment Station, 3909 Halls Ferry Road, Vicksburg, MS 39180-6199; e-mail: [email protected]. Dyntel Corporation, 3530 Manor Drive, Vicksburg, MS 39180. Received for publication March 15, 2002, and in revised form June 3, 2002. Greg Bugbee, Connecticut Agricultural Experiment Station, Department of Soil and Water, New Haven, CT 06511; Gerald Smith, Aquatic Control Technology, Sutton, MA 01540. marigold growth. We conclude that there is limited potential for selectively controlling nuisance fanwort populations with fluridone where water marigold must be protected.