- classification : Fungi, Ascomycota, Dothideomycetes, Pleosporomycetidae, Pleosporales, Incertae sedis
- téléomorphe :  Herpotrichia
- English name: corky root

This soil-borne fungus , first described in Europe, is now present in production areas on several continents. It is a marker of so-called “tired” soils which have supported crops of tomatoes on several occasions and / or other sensitive crops, mainly vegetables. It is surprising to note that it has been reported in organic and mineral substrates of soilless cultures, while it does not have structures allowing it to spread easily. In addition to the yield losses it can cause (40 to 70% in heavily affected plots, or even more), it often forces producers to implement various costly measures to reduce its impact: soil disinfection, grafting , soilless cultivation .

Its importance in France is not negligible, especially in crops with "tired" soils on which tomatoes have returned too frequently. This is the case under shelters in plastic tunnels in particular, but also for the production of industrial tomatoes. In intensely infested soils, plant growth is severely disturbed. It does not seem to be present in France in soilless crops.

Few data are available regarding the biological and genetic variability of Pyrenochaeta lycopersici . Three groups of strains would have been defined according to their optima thermal : cold, temperate and hot strains. These groups do not seem to present a great molecular variability according to the scarce work on the subject.

It should be remembered that the fungus Rhizopycnis vagum DF Farr was recently reported in Italy as responsible for corky roots on tomatoes . In this country it is sometimes co-isolated from tomato roots at the same time as P. lycopersici . A comparable situation was observed in Canada, Setophoma terrestris ( Pyrenochaeta terrestris ) being also associated with symptoms of corky roots on tomato.