Populations of Longidorus elongatus and other plant parasitic nematodes were much reduced after raspberry canes were incorporated into the soil. This reduction in numbers of nematodes was thought to be due to a toxic substance in the plant material, and it was shown that aqueous extracts of raspberry roots and canes were toxic to L. elongatus. The chemical involved has not been demonstrated but it is observed that raspberry contains large amounts of tannin and a number of polyphenols derived from other plant tannins were shown to be nematicidal.