Biology, epidemiology

The Pratylenchus spp. are likely to overwinter 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. P. penetrans has been recorded on more than 160 different plants.


- Penetration and invasion

These nematodes (larvae or adults) penetrate the roots by drilling holes with their mouth stylets. They gradually invade the cortex, destroying cells and digging cavities during their nourishing activities. In these nematodes, all stages are mobile within the tissues of the cortex; it is for this reason that they are qualified as "endo-migratory" 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 Pratylenchus penetrans , the duration of a complete cycle (from one adult to another adult) can last from 30 to 86 days, depending mainly on temperature conditions.


- Conditions favorable to their development

Their thermal requirements fluctuate depending on the species of Pratylenchus . As regards P. crenatus and P. penetrans , the higher the temperatures in the soil, the more active they are, within a temperature range of 18 to 30 ° C. P. crenatus would prefer rather heavy, loamy soils, while prefer P. penetrans would sandy soils. The latter would survive less well in dry soils than in the same wet soils. It would reproduce best at a pH between 5.2 and 6.4.

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