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|Title:||Endothall concentration and exposure time relationships for the control of eurasian watermilfoil and hydrilla|
|Authors:||Aquatic Plant Control Research Program (U.S.)|
Netherland, Michael D.
Green, W. Reed.
Getsinger, Kurt D.
|Publisher:||Environmental Laboratory (U.S.)|
Engineer Research and Development Center (U.S.)
Abstract: Herbicide concentration and exposure time relationships were determined for endothall (the dipotassium salt of 7-oxabicyclo [2,2,1] heptane-2,3-dicarboxylic acid) and control of Eurasian watermilfoil (Myriophyllum spicatum L.) and dioecious hydrilla (Hydrilla verticillata (L.f.) Royle) under controlled-environment conditions. Sixteen endothall concentration and exposure time combinations were tested for Eurasian watermilfoil. Concentrations ranged from 0.5 to 5.0 mg acid equivalent (ae)/l; exposure times ranged from 2 to 72 hr. Twenty-seven endothall concentration and exposure time combinations were tested for hydrilla. Concentrations ranged from 1.0 to 5.0 mg ae/l; exposure times ranged from 6 to 72 hr. Plant control was based on shoot and root biomass harvested at the end of the experiments. Weekly visual injury ratings were used to characterize efficacy during the course of the experiments. Plant control increased (biomass decreased), as either concentration or exposure time increased. A threshold level was reached in which a concentration/exposure time combination provided satisfactory control. Severe Eurasian watermilfoil injury (>85% biomass reduction) occurred when exposed to 0.5 mg ae/l for 48 hr, 1.0 mg ae/l for 36 hr, 3.0 mg ae/l for 18 hr, and 5.0 mg ae/l for 12 hr. Severe hydrilla injury (>85% biomass reduction) occurred when exposed to 2.0 mg ae/l for 48 hr and to 3.0, 4.0, and 5.0 mg ae/l for 24 hr. The 1.0-mg ae/l treatment failed to produce severe hydrilla injury at the maximum exposure time tested of 72 hr. Increased control of Eurasian watermilfoil and hydrilla is likely for treatments in systems where plants remain in contact with endothall concentrations and exposure times greater than the developed threshold levels.
|Appears in Collections:||Miscellaneous Paper|