Discusses problems in selecting the correct herbicide for use in controlling aquatic weeds, considering specificity, size of the market, fear of trace contaminants, and herbicide resistance in weeds. Also summarizes some successful herbicides, providing a table listing mode of action of some herbicides used for control of aquatic plants. (JN)

Uses members of the Cruciferae family such as radishes (Sp. Raphanus), to describe a process termed allelopathy by which a plant uses a chemical compound that escapes into the environment to harm another plant. Tips are provided for easy use in the classroom. (ZWH)