Biology, epidemiology

- Conservation, sources d'inoculum

The Meloidogyne spp. persist in the soil for more than two years, in the form of egg masses protected by a white to brown mucilaginous matrix which can be seen on the surface of the galls with a binocular magnifying glass.

They are very polyphagous and attack very many plants, cultivated or not (more than 5500 plants), on which they ensure their multiplication and their conservation: chrysanthemum, carnation, rose bush, kiwi, peach, banana tree, tomato, pepper, eggplant, lettuce , melon, cucumber, squash, artichoke, carrot, celery, beans, sweet potato ...


- Penetration and invasion

The larvae second instar , attracted by root exudates and other compounds, enter the roots and migrate to the vascular system through the cortex, between cells. During their bites, they secrete enzymes that cause migration in the root and the development of giant cells that will contribute to their nutrition. Larval development continues at the same time as the root swells. Ultimately, a gall surrounds a large female piriformis (Figures 1 and 3). This produces many eggs (300 to 3000, between 400 and 500 on average) which are emitted outside the root, embedded in a mucilaginous matrix. Several generations take place during a season, and the infestation can reach 100,000 to 200,000 larvae / kg of soil.


- Dissemination

Many eggs and larvae (Figure 4) can be passively transported by runoff, drainage and irrigation water from diseased plants. The larvae actively move short distances in moist soils. Dissemination is possible via dust from contaminated soil carried by the wind to neighboring plots. Contaminated plants, tillage tools and machinery also perform this function.


- Conditions favorable to their development

In general, nematodes are active in hot and humid soils and see their development slowed down in cold soils. Meloidogyne arenaria and to a lesser extent M. incognita appreciate the relatively high temperatures (18 to 27 ° C) which are encountered in light and sandy soils. M. javanica tolerates warmer temperatures, while M. hapla cooler conditions prefers . In general, their activity is greatly reduced, or even blocked below 5 ° C and above 38 ° C. The density of the inoculum of the soil, the manifestation of various stresses for the plants (compacted or not very humid soil, nutritional deficiency, attacks of various pests ) also influence the attacks of nematodes and the severity of their symptoms.