Submitted to: Pesticide Outlook
Publication Type: Review Article
Publication Acceptance Date: 10/15/2005
Publication Date: 12/1/2005
Citation: Dayan, F.E., Netherland, M. 2005. Hydrilla, the perfect aquatic weed, becomes more noxious than ever. Pesticide Outlook. 16(6): 277-282.
Technical Abstract: Hydrilla [Hydrilla verticillata (L.F.) Royale] was introduced in Florida lakes 50 years ago and is now one of the most serious aquatic weed problems in the United States. This plant possesses numerous mechanisms of vegetative reproduction that enables it to spread very rapidly. Management of this weed has been achieved with the herbicide fluridone. Fluridone, a phytoene desaturase inhibitor, is the only herbicide approved by the USA-EPA for systemic treatment of large water bodies. At least three fluridone-resistant biotypes of hydrilla have recently been identified in Florida lakes. Resistance is the result of one of three independent somatic mutations at the arginine 304 codon of the gene encoding phytoene desaturase. The specific activities of the three purified phytoene desaturase variants are similar to the wild-type enzyme. This is the first known instance of evolution of resistance to phytoene desaturase inhibitors in higher plants. As hydrilla spread rapidly to lakes across the southern United States in the past, the expansion of resistant biotypes is likely to pose significant environmental challenges in the future and require new management approaches to control this aquatic weed.