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Effect of Paclobutrazol and Waterhyacinth Weevil (Neochetina eichhorniae) on Plant Growth and Leaf Dynamics of Waterhyacinth (Eichhornia crassipes)

Published online by Cambridge University Press:  12 June 2017

Thai K. Van
Aquatic Plant Manage. Lab., Agric. Res. Serv., U.S. Dep. Agric., Fort Lauderdale, FL 33314
Ted D. Center
Aquatic Plant Manage. Lab., Agric. Res. Serv., U.S. Dep. Agric., Fort Lauderdale, FL 33314


Waterhyacinths grown outdoors were treated with combinations of 0 or 22 kg ai ha-1 of the plant growth retardant paclobutrazol and 0, 25, or 250 waterhyacinth weevils per culture tank under conditions of low (25% coverage) or high (100% coverage) plant densities. The low plant density treatments simulated a regrowth or colonization situation. Weevil feeding activity, canopy height, plant volume, leaf production, and leaf mortality were monitored biweekly for 22 weeks or until all plants had died. In high plant densities, weevil infestations increased leaf mortality rates while decreasing production rates, causing eventual plant death. At low plant densities, waterhyacinth plants partially compensated for weevil feeding by increased leaf production rates, thus enabling them to survive until the end of the study. Paclobutrazol reduced canopy height for about 3 months but had little effect on weevil feeding intensities. Combinations of weevils and paclobutrazol gave complete control of waterhyacinths regardless of plant densities. The combined effects were synergistic, with accelerated leaf mortality rates exceeding production rates leading to early plant death. This study demonstrated the potential for increasing effectiveness of waterhyacinth weevils using integrated strategies.

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Copyright © 1994 by the Weed Science Society of America 

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