Main symptoms

More or less large and regular galls on the roots characterize the presence of Meloidogyne spp. (figures 1 to 8). The nature and importance of galls depend on the species and the soil inoculum rate of these nematodes (Figure 4). The galls produced by M. hapla are rather small because it invades the apical meristems and therefore affects a smaller proportion of the roots, while those induced by M. arenaria are the size of a pearl and affect almost all the roots. The other two major species cause large galls sometimes covering all the root systems.

These root alterations disrupt the development of lettuce which exhibits reduced growth. In addition, some leaves can be chlorotic and wilt sometimes occurs during the hottest hours of the day.

A cross section of the galls makes it possible to highlight the mature females, thus confirming the parasitism of these nematodes (figure 9).