Some herbicides can be harmful to people, animals and the environment when they end up in the water. These herbicides should definitely not be sprayed near waterways and also should not be sprayed in areas where the herbicides can seep into the soil and contaminate the groundwater. There are some forms of herbicides that are safe when sprayed on soil over groundwater and can even be sprayed near waterways. Always double-check a herbicide's usage restrictions, even if it was once approved for use near water, since herbicide regulations change.
Metsulfuron, known by the brand name Ally, is used on blackberry, dewberry, multiflora rose, ash cherry, elm, and willows. This herbicide is safe enough that animals can graze off of the plants that have been sprayed, according to Alabama A&M University.
Triclopyr Ester + 2,4-D Ester,
Triclopyr ester + 2,4-D ester, sold under the name Crossbow, is sprayed on the bark of trees. This herbicide suppresses the growth of oaks, locust, willow, blackberries and mulberry, according to Alabama A&M University Extension. This herbicide can be used near water.
Triclopyr amine, sold as Garlon 3A, is a herbicide that is dissolved and diluted before being sprayed on to the foliage of oak, ash, willow and blackberry trees. This herbicide will not harm waterways, according to Alabama A&M University. A variation, sold commercially as Garlon 4, is used on blackberry, sweetgum, osage orange, blackgum, locust and hickory.
Glyphosate is a herbicide that can be used in water and is used to kill aquatic plants such as water lilies and plants close to the shoreline like purple loosestrife. However, the herbicide must only be sprayed directly on the plant's leaves, according to the State of Washington Department of Ecology.
Fosamine, sold as Krenite S, is commonly used near waterways. Locust, sumac, oaks, and sycamore do not produce leaves in the spring if the fosamine is applied to the leaves before they begin to change colors.
Imazapyr is a herbicide that is used to kill emergent plants like spartina, reed canarygrass, and phragmites. It will also kill water lilies, according to the Washington State Department of Ecology. Focus imazapyr spray only on the plants that are supposed to be killed to reduce the risk that the herbicide has to nearby plants.
Fluridone is a herbicide that is used in water. This herbicide should not be used in water that flows rapidly such as with streams, since rapidly flowing water can dilute the fluridone to the point where it is no longer effective. It is used to kill the Eurasian watermilfoil.
This liquid form of dimethylamine salt is used to kill broad-leaved plants both on land and in the ocean, according to the State of Washington Ecology Department. However, this herbicide cannot be used in waters where there are endangered salmon species.