Biology and Epidemiology

- Survival and sources of inoculum

Meloidogyne spp. can survive in the soil for more than two years, in form of egg masses protected by a mucilaginous matrix. They are very polyphagous and attack numerous cultivated and non-cultivated plants through which the nematode proliferation and survival is ensured.


- Penetration into the plant and invasion

The second instar larvae, attracted by root exudates penetrate roots and migrate into the vascular system. During their punctures on cells, they secrete enzymes and hormones which stimulate the development of giant cells from which the nematodes feed. Larval development continues at the same time than the root swells. At the end, a gall (knot) is formed, it contains a large female pyriform (figure 1). It produces many eggs (400 to 500 on average) which are placed outside the root, in a gelatinous matrix.


- Dissemination

Many eggs or larvae from the diseased plants can be transported passively by water runoff, drainage and irrigation. The larvae move actively over short distances in wet soils. Dissemination may occur through contaminated dust, which is carried by strong wind to neighboring fields. This nematode can also be spread through contaminated plants, tools, and vehicles.


- Favourable conditions for the nematode development

M. incognita and M. arenaria are favoured by relatively high temperatures (18-27 ° C) typical of light and sandy soils. M. javanica tolerates higher temperatures, than M. hapla. Tests conducted in the United States have shown that the previously planted crop could particularly favour some species occuring in tobacco. M. incognita appeared predominant after corn and cotton rotations, while M. arenaria was predominant after soybeans and peanuts.