Four groups of aquatic weeds are described: algae, floating weeds, emersed weeds, and submersed weeds. Specific requirements for pesticide application are given for static water, limited flow, and moving water situations. The secondary effects of improper pesticide application rates are given for static, limited flow, and moving water, and the effects of faulty application are given. Finally, surface applied, total water column, and bottom acre-foot application are discussed. (BB)