Main Symptoms

Large and regular shape root galls characterise the presence of these nematodes (figures 1 to 3). The nature and significance of galls depend on the species and the density of soil inoculum. The galls caused by Meloidogyne hapla are rather small and affect a small proportion of the roots, while those induced by M. arenaria are of a pearl size and are present all over the root system. The other two major species cause large galls occasionally covering the entire root systems.

These malformations disturb the root development of plants which show reduced growth and wilt during the hottest hours of the day.

Some of the information on the worldwide distribution of the disease is obtained from surveys conducted by CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco). The reliability of the information is not confirmed in all countries.