Selective Control of Eurasian Watermilfoil and Curlyleaf Pondweed in Noxon Rapids Reservoir, Montana: Herbicide Small-Plot Evaluations, 2010-2011.

Noxon Rapids Reservoir, Montana, is one of several large impoundments on the Lower Clark Fork River, stretching for over 48 km (30 miles) with a surface area of approximately 3,120 ha (7,700 acres). Management strategies were evaluated for their effectiveness in controlling invasive plant problems in the reservoir, specifically with Eurasian watermilfoil and curlyleaf pond- weed. A 3-year field program was developed to evaluate the effectiveness of aquatic herbicides to selectively control the invasive plants. The herbicide endothall (Aquathol K) was applied to four plots totaling 5.5 ha (13.6 acres) at 3000 g ai/L (3 ppm); diquat (Reward ) was applied to four plots totaling 3.3 ha (8.1 acres) at 370 g ai/L (0.37 ppm); and a combination of both products was applied to four plots totaling 4.7 ha (11.5 acres), with endothall at 1500 g ai/L (1.5 ppm) and diquat at 190 g ai/L (0.19 ppm). Herbicides were applied by boat using a variable-depth injection system. Aqueous herbicide dissipation was monitored in selected plots. Bulk water exchange processes were also measured. Quantitative surveys were conducted in each plot to assess the plant community at pretreatment, and at 6 weeks and 52 weeks post treatment.
Personal Author Getsinger, K. D.; Skogerboe, J. G.; Wersal, R. M.; Madsen, J. D.; Nawrocki, J. J.
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