Depending on the herbicide used, it may take several days to weeks or several treatments during a growing season before the herbicide controls or kills treated plants. Rapid-acting herbicides like Aquathol may cause low oxygen conditions to develop as plants decompose. Low oxygen can cause fish kills. To be most effective, generally herbicides must be applied to rapidly-growing plants. Some expertise in using herbicides is necessary in order to be successful and to avoid unwanted impacts.
Many people have strong feelings against using chemicals in water.
Find out what your neighbors think about chemical use before deciding to treat your water plants with herbicides. Some cities or counties may have policies forbidding or discouraging the use of aquatic herbicides. Check before hiring an aquatic herbicide applicator. Permits A permit called a short-term modification to water quality standards is needed from the Department of Ecology . The permit usually takes 60 to 120 days to process.