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Poovey, A.G. and S.H. Kay, 1998. The Potential of a Summer Drawdown to Manage Monoecious Hydrilla, North Carolina State University. Reprinted from Journal of Aquatic Plant Management (1998) 36(2): 127-130 The Potential of a Summer Drawdown to Manage Monoecious HydrillaA summer drawdown to manage monoecious hydrilla (Hydrilla verticillata (L.f.) Royle) was investigated using a mesocosm system. The objectives were: to determine the length of drawdown required to kill vegetative biomass; to evaluate plant recovery in terms of regrowth and production of propagules following the drawdown; and to examine the influence of hydrosoil characteristics on plant response to drawdown. Hydrilla tubers were collected from the field, sprouted in the laboratory, planted in sand or silt loam soil, and placed in concrete tanks. A drawdown was simulated by taking plants out of the tanks, exposing them to ambient conditions for one to four weeks, and returning them to the mesocosms until the end of the growing season. A one-week drawdown was sufficient for killing hydrilla on sand; no regrowth or tuber production occurred. A one-week drawdown on silt loam was not effective in desiccating the root system and preventing regrowth; these plants produced the same amount of biomass and twice as many tubers as the reference plants. A drawdown of two weeks or longer, however, suppressed hydrilla regrowth and greatly reduced tuber numbers. Few turions were found on reference plants at the end of the season. Plants subjected to drawdown did not pro duce turions. These results suggest that a short-term summer drawdown on might be useful in monoecious hydrilla management; however, hydrosoil type may determine length of drawdown required for complete soil desiccation and plant kill. Entire Paper |