Utilization of Herbicide Concentration/Exposure Time Relationships for Controlling Submersed Invasive Plants on Lake Gaston, Virginia/North Carolina

摘要

Lake Gaston is a large, multiple purpose impoundment on the Roanoke River between eastern North Carolina and Virginia. Invasive plants have been increasing on the lake since 1982. By 2002, over 1,200 ha of the lake were infested with several invasive plants, and an integrated management program (herbicides and grass carp) was underway. To improve herbicide performance on the lake, this study focused on three phases for controlling the lake's invasive submersed vegetation (the plants targeted were monoecious and dioecious hydrilla; Eurasian watermilfoil; egeria; and the bluegreen alga, lyngbya; non-target plants evaluated were vallisneria and southern naiad.) Phase one summarizes herbicide dose-response interactions (concentration and exposure time (CET) relationships) for controlling these plants using older aquatic herbicides; phase two evaluates CET relationships for new aquatic herbicides; and phase three provides interim management guidance for Lake Gaston. Product-specific CET information is best utilized when combined with site-specific water exchange patterns found in plant stands targeted for chemical applications. Prescriptive treatments can then be developed to selectively remove invasive plants. Results from evaluations showed that control of target plants was dependent upon product specific herbicide CET relationships, with efficacy ranging from poor to excellent. Information provided in this report can be used for developing prescriptive treatment strategies for selectively controlling invasive plants on Lake Gaston. Recommendations for specific herbicides should be viewed as a 'best fit' based on current information. This interim chemical control guidance should be refined once site-specific water exchange processes are determined for treatment sites on Lake Gaston.