The fight against Fusarium oxysporum f. sp. radicis-lycopersici is easy because this fungus not keeps for a very long time in soils and substrates, and it recolonizes them very quickly when they have been disinfected. Also, for the control of the terrestrial fungus to be effective, it will be necessary to combine the whole battery of measures and methods, allowing to eliminate it or to limit its development.

• During cultivation

No control method is efficient enough to control this disease when it is observed during cultivation. In order to keep the plants alive as long as possible, they should be treated quickly, by watering at the foot or via the localized irrigation system, with an fungicide * approved ( e-phy ). The effectiveness of these treatments is not always important. It should be noted that strains of F. oxysporum f. sp. radicis-lycopersici resistant to benzimidazoles have been detected in cultures where these products have been used repeatedly.

In soil, the ridging of the plants allows the emission of adventitious roots which will come to replace the more or less rotten diseased roots. In soilless culture, peat can be added to the crown of plants, for the same reason as above. In this type of crop, the first fruits must be harvested quickly in order to "relieve" the plants somewhat. Plants should not be irrigated with too cold water.

In the process of cultivation, the first diseased plants can be removed carefully . To do this, they must be placed in a plastic bag to avoid any contact with other healthy plants. They will be quickly destroyed thereafter. If an outbreak is present in the culture, it can be tagged, quarantined, and worked on separately. Carts and harvest containers will not pass through this fireplace.

Visitors will not be allowed in the affected areas. The footbaths will be installed in front of each entrance, the disinfectant solution should be changed frequently.

It is quite common to bury crop residues in the soil after harvest. The buried plant tissues are abundantly colonized by F. oxysporum f. sp. radicis-lycopersici which produces numerous chlamydospores there. The removal of plants with root systems limit this phenomenon and helps reduce the amount of inoculum left in the plots. Plant debris will not be piled up and kept near plots or shelters where tomatoes will be grown later. Indeed, they constitute important sources of inoculum which should be destroyed as quickly as possible. Otherwise, the wind, the intervening parties, certain insects will “take care” of bringing in F. oxysporum f. sp. radicis-lycopersici in crops. If this cannot be done otherwise, the pile of debris will be covered with a plastic film in order to constitute a mechanical barrier.

• Culture suivante

We will avoid producing tomatoes in plots already affected. Of crop rotations with non-host crops (such as corn or similar crops) will help prevent the onset of this disease or limited. To be effective, they must be long enough. Avoid bringing in the eggplant, pepper and some of the vegetables mentioned above in rotation with the tomato. We prefer lettuce which does not seem sensitive.

In cultivation under shelters, in particular above ground, the entire farm must be disinfected in order to get rid of as many more or less adherent propagules as possible, liable to contaminate the new plants. It will therefore be necessary to disinfect the surface of the internal structures of the shelters. Formalin, an excellent surface disinfectant which acts very quickly in the form of steam, is sometimes used. Other products can be used ( e-phy ). Bags, substrate cubes and other materials that may have been contaminated should be disposed of. If they are reused, they will need to be disinfected beforehand.

The soil disinfection has only fleeting efficiency and unsatisfactory. Indeed, like all Fusarium , Forl very quickly recolonizes disinfected soils. In addition to steam, several fumigants can be used: chloropicrin, metam-sodium, dazomet… The nature of the soil and its organic matter content influence the effectiveness of these fumigants. Calcium cyanamide would reduce the inoculum of the soil. The combination of metam-sodium and formalin has given good results in Israel. The effectiveness of the disinfection of substrates of soilless cultures is often uncertain. It makes more sense to eliminate them and start again with a new substrate. The soil of the crop should be concreted or covered with plastic film. This should be replaced as soon as tears appear. This will make it possible to isolate the crop from the soil and prevent airborne contamination via soil dust in particular. For the same reasons, the water tanks, the nutrient solution trays should be covered.

The solarization would also have some efficacy. It would sometimes be quite partial, because F. oxysporum f. sp. radicis-lycopersici is less sensitive to heat than other soil pests such as Pythium spp., Sclerotium rolfsii for example. Solarization is therefore often associated with other biological control means (antagonistic fungi such as Trichoderma harzianum ) or chemical (low-dose fumigants of dazomet, metam-sodium, etc.).

The ozone , used by water ionization and associated with Trichoderma sp., Would reduce attacks by F. oxysporum f. sp. radicis-lycopersici . Certain composts would also limit its effects. Substrates based on bark fiber of Chamaecyparis obtusa or Cryptomeria japonica would slow its development. The incorporation of certain whole plants in the soil, such as rice, soybeans or lettuce would reduce the incidence of this Fusarium on tomato.

It will be essential to use healthy plants . They must be produced with a healthy substrate, and the clods will not be placed on the ground, in the nursery. Nurseries should not be located near plots or in shelters where crops have already been affected by the disease. Aerial contaminations of the plants are always possible. Avoid over-watering the plants and injuring them when setting up in the field. The trays and boxes reused to contain the plants will be disinfected. We will be particularly vigilant about their sanitary quality. Those from farms affected by this Fusarium wilt will not be accepted. The plants will be installed in warmed soil, plastic mulch will only be put in place at this time.

The tools used to tillage in contaminated plots will be thoroughly cleaned before use in other healthy plots. It will be the same for the wheels of the tractors. Thorough water rinsing of this material will often be sufficient to rid it of infested soil.

It will be necessary to be wary of the sanitary quality of the water used for the preparation of the nutrient solution and / or the irrigation of the plants, especially if it comes from an irrigation canal, a watercourse, 'a basin ... that may have been contaminated.

If the nutrient solution is recycled, it can be disinfected . Several methods can be used: chlorination, iodination, ozonation, biofiltration, UV rays, TiO photocatalysis ₂ … The efficiency spectrum of these different methods seems quite broad and includes several fungi, in particular this Fusarium . They are not all entirely satisfactory. Indeed, some of them reveal a partial effectiveness and sometimes drawbacks for the production systems (interference with mineral nutrition, in particular ferric…). The pipes of the drip network will need to be cleaned or replaced. The deposits will be removed with an acid solution, and the disinfected circuit will then be rinsed with water. In greenhouses where the nutrient solution is recycled, the measures taken will be more important. The circuit will need to be disinfected several times to be sure to get rid of F. oxysporum f. sp. radicis-lycopersici .

The be use of ammoniacal nitrogen should avoided , and the pH of the soil should be maintained at 6 or 7. The stakes should be disinfected.

The demonstration of aerial contaminations via wounds now makes it necessary to consider protection of the foliage and not to neglect the possible sporulation of the fungus on the stem causing the aerial inoculum.

The most effective method of controlling this root blight is to use resistant varieties . A dominant gene " Frl ", derived from Lycopersicon peruvianum and located on chromosome 9, confers high level resistance. The close association of this gene with “ Tm-2 ” (tobacco mosaic virus resistance gene) made it possible to facilitate the selection of resistant varieties. Several KNVFFr-type tomato rootstocks are now resistant to this Fusarium wilt. They make it possible to cultivate, in infected soils and in soil-less cultivation, varietal types for which resistant varieties are not yet available.

Several bacteria would interfere with this root Fusarium, either directly or through the tomato: Pseudomonas fluorescens (whose effectiveness is influenced by zinc), P. chlororaphis, P. putida (would induce an acquired systemic resistance to F. oxysporum f. sp. radicis-lycopersici in tomato), Bacillus megaterium and Burkholderia cepaciae (would control F. oxysporum f. sp. radicis-lycopersici in association with a supply of carbendazim).

In addition, several fungi have made it possible to control the development of F. oxysporum f. sp. radicis-lycopersici , and therefore the expression of this root disease: Trichoderma harzianum , Fusarium spp. non-pathogenic (avirulent strains of Fusarium oxysporum and F. solani), a binucleate and hypovirulent strain of Rhizoctonia solani, Pythium oligandrum, Gliocladium roseum (alone or in combination with benomyl intake). Let us add that mycorrhizal fungi belonging to the genus Glomus ( G. intraradices …) reduce the severity of the symptoms of this root fusarium in tomato.

Finally, it should be noted that several oils volatile and non-volatile substances would negatively influence the development of F. oxysporum f. sp. radicis-lycopersici on tomato.

The cultural and morphological characteristics of F. oxysporum f. sp. radicis-lycopersici are no different from that of F. oxysporum f. sp. lycopersic .