Treatment at water alkalini-ties of 20 ppm is extremely risky. The toxicity of copper sulfate to fish increas-es as water temperature increases. Avoid copper sulfate applications during hot summer months. Copper that is held in an organic com-plex is known as chelated copper. Chelated copper formulations do not readily precipitate in high alkalinity waters, but stay in solution and remain active longer than copper sulfate.
Chelated copper is less corrosive to application equipment than copper sul-fate.
Due to its enhanced solubility, chelated copper is generally used at rates slightly lower than copper sulfate. Chelated copper formulations are slightly less toxic to fish than copper sulfate. An approved nonionic surfactant is required when diquat is used as a foliar application. Diquat is tightly bound to clay micelles and is not effective for weed control in muddy water. Diquat quickly kills plants and should be used as a partial pond treat-ment for dense vegetation.