Proteases, lipase, and chitinase killed Tylenchorhynchus dubius in vitro and in soil. T. dubius was more susceptible to the enzymes than Pratylenchus penetrans. Papain was the most effective protease, and other enzymes were less effective. Heating enzymes to 80.degree. C for 10 min greatly reduced nematicidal effectiveness. Scanning electron micrographs showed that papain and chitinase produced structural changes in the cuticle of T. dubius. Lipase removed a thin outer layer. Papain removed material filling the striata, or furrow, between the horizontal bands. When added to soil, chitinase, lipase, collagenase, and proteases (papain and bromelain) decreased motility of T. dubius populations up to 75%. Bromelain was the most active in soil against T. dubius, and collagenase was the most active in soil against P. penetrans.