Root-knot nematodes on protected crops

Root-knot nematodes (Meloidogyne spp.) cause galls to be formed on the roots of tomato (Fig. 86.1), cucumber, and sometimes lettuce, dwarf French bean, chrysanthemum and various ornamental plants grown under protection. These swellings, which vary from the size of a pin-head to that of a walnut, are the plant’s reaction to feeding by the nematodes in the root tissues. The galls often merge with one another, resulting in completely deformed root-systems that have few active fibrous roots. With improved methods of crop protection, attacks occur much less frequently than in the past.