Response of Wild Rice to Selected Aquatic Herbicides

摘要

The invasion of exotic plants such as Eurasian watermilfoil (Myriophyllum spicatum L.) has contributed to the decline and displacement of native wild rice (Zizania aquatica L.) populations in many U.S. water bodies. Wild rice is a popular food source for both man and animal and provides important habitat for waterfowl, invertebrates, and fish. Herbicides can be successfully used to manage invasive weeds such as Eurasian watermilfoil; however, the potential impacts of such chemical management techniques on native plants (including wild rice) are not well documented. This outdoor tank study was conducted to examine the effects of several aquatic herbicides on the growth and survival of wild rice and to determine whether nontarget herbicide efficacy is influenced by wild rice growth stage. Aquatic formulations of the herbicides diquat, endothall, fluridone, and 2,4-D were applied at varying rates and contact times to three growth stages of wild rice. Results showed that degree of herbicide injury varied with plant growth stage. Wild rice treated at younger growth stages (early tillering or seedling stages) was more sensitive to chemical treatment than plants treated at later stages of development. Regardless of product or rate, herbicide treatment did not affect wild rice plants when applied at the mature growth stage (late tillering and flowering). Of the herbicides evaluated, wild rice was most sensitive to 2,4-D. Rates as low as 1 mg 2,4-D L- significantly inhibited tiller, seedhead, and dry weight biomass production in young wild rice. Dry weight of young wild rice was also reduced following exposure to endothall, diquat, and fluridone; however, seedhead and tiller production was not influenced by these products.