• During cultivation

If you observe symptoms of corky roots during cultivation, it is unfortunately too late to intervene effectively on the crop. Indeed, there is no effective way to eliminate the parasite present on the roots of plants without permanently altering them.

In order to try to keep the plants alive as long as possible, you should:
- to butter them in order to promote the emission of adventitious roots which can replace the old damaged roots. In soil-less cultivation (on peat or on pozzolan + peat) during serious attacks, peat can be added locally to the collar to allow additional rooting. Sawdust is sometimes used;
- to bathe them during the hottest periods of the day to avoid excessive and uncompensated evaporation, leading to wilting, drying out and death of the plants;
- monitor carefully the irrigation . Indeed, if the plants wither, it is not necessarily linked to a lack of water, but rather to root alterations due to Pyrenochaeta lycopersici . In some cases, growers tend to increase irrigation to respond to wilting, leading to amplification of root lesions through asphyxiation.

Note that a fungicide * can be used as a soil treatment at the foot of plants in order to limit the development of this telluric disease ( e-phy ).

We also advise you to eliminate and destroy carefully diseased plants and their root systems, in progress, but especially at the end of cultivation. This will prevent them from being subsequently buried in the soil and from enriching the inoculum of P. lycopersici already present.

• Next crop

If the nurseries are carried out each year in the same shelter, it will be essential to put in place the hygiene measures recommended in the Clavibacter michiganensis subsp. michiganensis . To produce your plants, we advise you to use healthy substrates (disinfected), to avoid placing the clods directly on the ground because they often become contaminated in contact with the latter, in particular if it has not been disinfected.

The crop rotations are interesting when they performed preventively, before the soil is heavily contaminated. In the latter case, their effectiveness is relative because the fungus keeps for a long time in the soil. In addition, it can multiply there thanks to various alternative hosts. Of course, care should be taken not to introduce sensitive plants into the rotations. The soil must be well worked, a good subsoil will allow the roots to access new layers.

Heavily contaminated soils should be disinfected . A fumigant can be used ( e-phy ). If this fumigant is more or less effective, however, it poses material problems and causes a number of disadvantages:
- destruction of natural microorganisms antagonists of certain pathogenic agents;
- increased receptivity to parasites in disinfected soil;
- appearance of toxicity phenomena (excess of exchangeable manganese, excess ammonia following complete or partial blockage of nitrification, etc.).

Note that in some countries, soil treatments before planting have been carried out with fungicidal solutions.

In sunny regions, solar disinfection of the soil (solarization or pasteurization) is increasingly used to control P. lycopersici . It consists of covering the floor to be disinfected, which will have been very well prepared and moistened beforehand, with a polyethylene film 35 to 50 µm thick. This is kept in place for at least a month at a very sunny time of the year. This method is economical, efficient, and makes it possible to control the colonizing fungi of the superficial zone of the soil. Steam disinfection is also effective.

If the soil is not disinfected, the attacks of can be delayed P. lycopersici by placing the plants in warmed soils and / or by increasing the volume of the clods which will be prepared with a healthy substrate.

In affected soil-less crops, it will be necessary to change the substrate and try to understand why this fungus, which does not have any dissemination structures, could have contaminated the substrate. In this case, we must particularly monitor the potential sources of contamination: plants, soil dust, irrigation water, etc.

Genetic resistance has been identified in accessions of Lycopersicon wild , such as L. hirsutum and L. peruvianum . That of L. hirsutum , polygenic with a dominant tendency, could not be transmitted to cultivated tomatoes. The recessive “ gene pyl ” (located on chromosome 3), for its part, could be introgressed into tomato from L. peruvianum . Thus, several tomato hybrids currently marketed are provided with it.

On the other hand, if you don't plan to disinfect your crop soils, grafting can be a highly effective solution, especially for under cover crops and home gardens. Several intra- or interspecific hybrid rootstocks are currently available.

Several fungi and bacteria antagonistic have been evaluated in vitro or in the field to control Pyrenochaeta lycopersici . Among them are Streptomyces griseoviridis, Gliocladium spp., Teratosperma sclerotivorum (Uecker, WA Ayers & PB Adams) S. Hughes (syn. Sporidesmium sclerotivorum Uecker, WA Ayers & PB Adams), Talaromyces flavus and Trichoderma harzianum .


* Chemical control : As the number of pesticides available for a given use is constantly changing, we advise you to always confirm your choice by consulting the e-phy site of the Ministry of Agriculture and Fisheries which is an online catalog of plant protection products and their uses, fertilizers and growing media approved in France. This also applies to all biological products based on microorganisms or natural substances.