- Conservation, sources d'inoculum

The Pratylenchus spp. are nematodes capable of overwintering in the soil, on and in living or dead roots. A large number of hosts house them, ensuring their conservation and multiplication at any time of the year. For example, Pratylenchus penetrans has been recorded on more than 400 different plants, making it certainly the most widespread species and the one with the most consequent economic repercussions. Among the many cultivated plants likely to harbor these Pratylenchus spp. let us point out the potato, many vegetables, the sweet potato, the sorghum, the oats, the sunflower, the alfalfa, the rice, the corn, the strawberry, fruit species and several weeds.


- Penetration and invasion

Nematodes (larvae or adults) penetrate the roots by drilling holes with their mouth stylets. They gradually invade the cortex, destroying cells and making cavities during their nutritive activities. In Pratylenchus spp., All stages are mobile within the tissues of the cortex, which is why they are called "endomigratory nematodes". Ultimately, the altered tissues harbor a large number of eggs, larvae and adults. A not insignificant proportion of the latter returns to the soil.


- Dissemination

From diseased plants, many eggs and / or larvae and / or adults can be passively transported by runoff, drainage and irrigation water to other plants. The larvae actively move short distances in moist soils. Dissemination is possible by dust from contaminated soil, carried by the wind to neighboring plots. Contaminated plants, tillage tools and vehicles also perform this function.

In P. penetrans , the duration of a complete cycle (from one adult to another adult) can last from 30 to 86 days, mainly depending on temperature conditions.


- Conditions favorable to their development

Their thermal requirements fluctuate depending on the species: for P. crenatus and P. penetrans , the higher the temperatures in the soil, the more active they are, in a range of temperatures between 18 and 30 ° C. P. crenatus would prefer rather heavy, silty soils, while P. penetrans would prefer sandy soils. The latter would survive less well in dry soils than in wet soils themselves. It would reproduce better at a pH between 5.2 and 6.4.

In general, the growing conditions unfavorable to the tomato favor the parasitism of these nematodes.