The Pratylenchus spp. cause numerous lesions of varying size, rather longitudinal, appear on the roots. Their coloration, linked to the formation of phenolic compounds in the tissues, varies from yellowish to reddish brown (figure 1). Eventually, larger or smaller portions of the cortex break down. When the attacks are severe, a large proportion of the root system can disappear.

Placed in this situation, the growth of the plants is not very vigorous; a variable part of the leaves turn yellow or even wilt at the hottest times of the day.

Observing the roots under a light microscope often makes it possible to observe, in or near the tissues, nematodes with a clearly visible stylet (Figures 2 and 3).