Efficacy of Bensulfuron Methyl on Eurasian Watermilfoil

摘要

Studies to evaluate the efficacy of bensulfuron methyl on Eurasian watermilfoil(Myriophyllum spicatum L.) were conducted in a 55-2 aquaria system under controlled-environment conditions. Forty-two bensulfuron methyl concentration and exposure time combinations were tested: concentrations ranged from 0 to 4,600 micrograms/i; exposure times ranged from 7 to 49 days. Chemical effectiveness was based on shoot and root biomass harvested at the conclusion of each experiment. Visual injury ratings were recorded weekly to characterize chemical activity. Herbicide injury was evident 1 week after application on all treatments and included one or more of the following symptoms: leaf chlorosis, deformed leaves on shoot tips, downward bending of leaves at upper nodes, stem necrosis, and formation of axillary buds. Following a 7-, 14-, 21-, 28-, 35-, 42-, and 49-day exposure period at concentrations ranging from 10 to 4,600 micrograms/l, plant biomass was reduced 10 to 90 percent compared with untreated plants. Increasing exposure time was more efficacious than increasing Bensulfuron methyl concentration. Younger milfoil plants (7 days old) were also susceptible to bensulfuron methyl application than plants that were allowed a 3-week pretreatment growth period. Bensulfuron methyl concentrations much much less 10 micrograms/l did not significantly reduce milfoil growth. Effects on roots were variable depending on concentration and plant age. Only treatments of 230 micrograms/l and higher inhibited root growth on plants grown for 3 weeks prior to treatment, whereas 50 micrograms/l was sufficient to reduce root growth of younger plants. Regrowth was observed on all treatments, indicating the potential for plant recovery.