Compositions and methods for controlling molluscs, members of the Gastropoda and Bivalvia classes which includes but is not limited to lactones, lactams, carbamates, amides, and/or carboxylic acid containing compounds as active ingredients and/or compounds derived from Pseudomonas and/or Erwinia. Also provided are methods and compositions for increasing the efficacy of chemical and biological control for invasive molluscs in open waters, power plants, and drinking water treatment facilities under coldwater conditions.