Pyrenochaeta lycopersici can be stored for several years in the soil on plant debris thanks to its mycelium and microsclerotia . Various cultivated alternative hosts, entering in rotation with the tomato, are able to accommodate and multiply it: lettuce, melon, cucumber, eggplant, pepper, bean, watermelon, spinach, strawberry, Carthamus tinctorius ... It is the same for several weeds. Note that this fungus, although it grows very slowly in the soil, can reach the deep layers.

It penetrates the root tissues and colonizes the cortex thanks to its mycelium, gradually causing its rotting or suberization.
 

This fungus unusually forms pycnidia of irregular size (Figures 1 to 3), producing conidia ellipsoid of 4-6 x 1-1.5 µm with setae on the spoiled roots of tomato. Given the rarity of these pycnidia, it can be assumed that these structures do not contribute much to the spread of P. lycopersici . The potential of dispersal this fungus is therefore very limited and depends above all on the activities linked to the cultivation of tomatoes. Thus, the dissemination can take place through contaminated plants and / or substrates, tools and tillage machinery. Unlike other fungi, it recolonizes rather soil slowly disinfected soils. It is for this reason that this practice is effective over a relatively long period of time, provided the method or fumigant has been chosen with care.

This fungus is rather known to thrive in cold climatic conditions . There still seem to be at least 2 types of strains : “cold” strains with a thermal optimum located between 15-20 ° C (northern European strains) and “hot” strains, still pathogenic at 26-30 °. vs. The latter are found in particular in several countries of the Mediterranean Basin (Tunisia, Lebanon ). The monoculture of tomatoes and / or the alternating or non-alternating production of sensitive crops in the same plot increases the rate of inoculum of the soil and favors its extension therein.

Last change : 07/08/21