Control of Waterhyacinth by Winter Drawdown

A winter drawdown was evaluated to control waterhyacinth (Eichhornia crassipes) in B. A. Steinhagen Reservoir in southeast Texas. A 1.8-m drop in water level was initiated on 15 December 1993 and maintained through 17 February 1994. Freezing temperatures were recorded on 19 days during the drawdown with the lowest temperature —6.7 C. A significant (P < 0.0001) reduction in waterhyacinth frequency of occurrence was indicated in line transects. Waterhyacinth areal coverage was reduced from 1,476 ha in June 1993 to 26 ha in June 1994.

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