Retardation of Hydrilla (Hydrilla verticillata) Regrowth through Chemical Control of Vegetative Reproduction

Abstract

Several chemicals were evaluated in the laboratory for their ability to inhibit growth of hydrilla [Hydrilla verticillata(L.f.) Royle] from tubers. Fenac [(2,3,6-trichlorophenyl)acetic acid] and dichlobenil (2,6-dichlorobenzonitrile) were effective in controlling regrowth in outdoor aquaria. In field tests, hydrilla regrowth was controlled for over 13 months by single applications of 34 kg/ha rates of fenac and over 48 months in one of three replicates treated with 11 kg/ha dichlobenil. Regrowth occurred in controls within 2 to 6 months. There were no differences in the number of viable propagules found in hydrosoil before and 13 months after treatments. Regrowth occurred from root-stocks and from tubers. Regrowth was associated with disappearance of the herbicides from water.