We do have not very effective control methods to combat this formidable bacteriosis. Every effort should be made to avoid introducing it into a farm. Once present in the latter, it will be necessary to be particularly reactive and persevering in order to eradicate it. The methods implemented will vary somewhat depending on the production context (open field, soil shelter, above ground shelter).

• During cultivation

As soon as the first diseased plant (s) are detected, a certain number of additional measures should be quickly put in place between them. Indeed, we do not have with regard to bacteria in general, and Clavibacter michiganensis subsp. michiganensis in particular, very effective protection methods at this stage. If few plants are affected, they should be carefully removed, taking care to remove all plant debris . They will be put in a plastic bag before taking them out of the culture and destroyed quickly. A quarantine zone will be established around this outbreak, and a cordon sanitaire put in place. No personnel will enter this area without authorization. It will be worked either by a specialized team, or after the rest of the culture, taking care to wear gloves and overshoes, to disinfect the tools during and after their use, and to change clothes when leaving the area.

Workers should wash their hands frequently with soap and water. It will be preferable that they wear gloves that they can disinfect by plunging their hands into a pocket containing a sponge soaked in a disinfectant (Virkon-S for example). Tools can be disinfected under the same conditions or by immersing them in alcohol or a bleach solution. We must also pay attention to the sanitary quality of the machinery and equipment used in cultivation.

Of footbaths must be installed at every entrance and filled with a disinfectant * ( e-phy ) . We will ensure that they are functional throughout the season. Workers must use them when entering and leaving the crop. We will avoid cultural visits as much as possible.

Staff must be made aware of the symptoms of the disease so that they can detect them early in their work and immediately notify the crop manager.

Of course, it is advisable to avoid irrigation by sprinkling and to reduce phytosanitary spraying as much as possible. It is also important to limit irrigation if it is too copious. In particularly affected production areas, one should be wary of irrigation water, it should not come from "surface water" that may have been contaminated; we prefer drilling water or water supply. In soil-less cultivation, if the nutrient solution is recycled, it must be disinfected because contamination is possible via the roots. Experiments have shown that if the solution is maintained for several hours at a pH of 4 to 4.5, C. michiganensis subsp. michiganensis , which does not appreciate acidic pH, is eliminated.

The applications of copper * on plants, long suggested, would bring only slight advantages , especially as the sprays carried out can have repercussions on the dissemination of the bacteria. Several forms of copper, t another product are authorized with regard to bacteriosis of the tomato ( e-phy ).

If many outbreaks are declared, the implementation of these measures is more difficult and tedious, their effectiveness more limited.

At the end of the culture , it is imperative to implement a " major cleaning " to have some chances of eliminating the bacteria from the farm. All plants must be eliminated. We will avoid generating a lot of organic waste (leaflets, fruits, seeds, roots, etc.) which will more easily pollute the farm.

In crops under cover, the substrates of soilless crops will be eliminated. When growing in soil, avoid burying too much plant debris. Shelter structures, heating pipes, pillars, as well as all equipment and tools that may have come into contact with diseased plants will be carefully cleaned with a high pressure jet. Disinfection will then be carried out with a commercial specialty comprising several of the products * ( e-phy ). Rinsing with uncontaminated water will be necessary.

In open field cultivation, plant debris , in particular the stems, must be eliminated and burned because they allow the bacteria to keep there for a long time, sometimes more than two years.

The debris will be burned, limed or transported to a recycling center, and in no case composted.

• Next crop

For the next crop, should be used healthy seeds . A number of seed disinfection methods are reported in the literature (maceration at the time of extraction, treatment with acetic acid, sodium hypochlorite, hydrochloric acid). While they reduce the amount of bacteria present on seeds, they do not completely eliminate them. In Israel, tomato seeds are systematically treated in a mixture of copper acetate, acetic acid, pentachloronitrobenzene, 5-ethoxy-3 (trichloromethyl) -1,2,4-thiadiazol and triton X-100 for 1 hour at 45 ° C. This method appears to be effective against the main bacteria affecting the tomato.

Seed lots are normally checked for the presence of C. michiganensis subsp. michiganensis . It seems technically difficult to be able to guarantee a total absence of this bacterium in the seeds. Be wary of seeds or plants of new lines or varieties intended for varietal trials; seeds are often produced in small quantities, sometimes in areas where the bacteria is endemic and protection methods insufficient or ineffective.

The nursery is a critical period. Indeed, the bacterium is often introduced into the latter through the seeds, and there can be an insidious development. Thus, latent contaminations can take place and go unnoticed. Subsequently, plants without symptoms, but contaminated, will be placed in the future culture. We will be particularly vigilant during the production of grafted plants which require numerous manipulations at the origin of the dissemination of this bacteriosis. It will be imperative in this case to put in place optimal hygiene measures and to have irreproachable seeds.

In traditional nurseries, the land or location used for seedlings will be disinfected with steam or with a fumigant. Excess humidity and all practices leading to the etiolation of the plants should be avoided. The manuring will not be excessive, nor the sowing densities too high. Environmental conditions unfavorable to the parasite will be maintained. Weeds in or near the nursery will be destroyed. We will do the same in the future plot.

Of copper treatments * from stage a sheet (200 to 300 g copper metal / hl as Bordeaux mixture) are advocated by some authors ( e-phy ).

We must not forget to remove or to disinfect all equipment (pots, stakes, string ...) used in the previous crop and that could come into contact with sick plants. For this, you can use bleach (titrating 12 ° chlorometric, soaking for 24 hours and rinsing with water) or formalin water (2 to 5% commercial formalin, soaking for 1 hour and storage under a 24-hour plastic film), or a commercial product * ( e-phy ) .

In soil cultivation, a long rotation , of at least 3 years, will be set up. The soil can be disinfected with a fumigant such as chloropycrin. Solarization would greatly reduce the damage caused by bacterial canker, as has been demonstrated in Greece. Weeds, especially those belonging to the nightshade family, will be destroyed.

In cases where the shelters are surrounded by infected plots, it may be advisable to grass them or to moisten them with sprinkles, so that dust cannot be blown away by the wind in the shelters.
Once again, footbaths will be installed at each entrance and filled with disinfectant. We will ensure that they remain functional throughout the season.

Several sources of resistance are reported in the literature. One of them, from Lycopersicon peruvianum var. 'humifusum' , was introduced in tomato via L. chilense . It is controlled by a dominant gene (" Cm "), which is not allelic to the gene present in L. hirsutum f. glabratum , and would be located on chromosome 4.

Further resistance was demonstrated in a cross between an accession of L. hirsutum ('LA 407') and L. esculentum . Two loci are responsible for this resistance: “ Rcm 2.0 ” located on chromosome 2 and “ Rcm 5.1 ” on 5.

In addition, crosses between L. esculentum ('LA 6 203') and L. parviflorum ('LA 2 133') would have revealed polygenic resistance. L. pimpinellifolium and L. racemigenum would have made it possible to obtain a high level resistance to bacterial canker.

Some resistant varieties of tomato are described in the literature, breeding programs are underway; however, their marketing is not yet topical!

Few products appear to be effective against this bacterium. The natural defenses activator (SDN), acibenzolar-S-methyl which is approved in France, would reduce the severity of the disease as well as the multiplication of the bacteria in plants. Let us point out several biopesticides which would reveal an anti- activity Clavibacter in vitro as in the field: Pseudomonas fluorescens, P. putida, Bacillus subtilis … Finally, for information, suspensions of garlic and peat humates would show a certain effectiveness.


* 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.