- During cultivation

No control method is really effective during cultivation on tomatoes.

If attacks occur in the nursery, the affected plants must be eliminated. Otherwise, planting them in the field will help ensure the spread of nematodes and the contamination of healthy soils.

During cultivation, in order to compensate for the partial dysfunction of the root systems parasitized by numerous galls, a hilling of the plants can be carried out. This will promote the development of adventitious roots which will momentarily take over.

Of bassinages will be realized during the hottest times of the day to prevent or reduce the wilting.

In the open field, it is imperative that the root systems of the attacked plants are removed from the plot and destroyed in order to avoid enriching the soil with nematodes. If this last measure is not possible, the roots will be put in the open air so that they undergo the effects of the sun. Likewise, several successive soil works carried out during the summer will help expose the nematodes to heat and kill them.

It should be noted that composting , which makes it possible to get rid of possible aerial pests present on the fruits, leaves and stems, is not as efficient on the roots. Indeed, this method does not completely eliminate the nematodes present on them.


- Next crop

To be effective, the fight against root-knot nematodes must involve, in a complementary manner, all the control methods proposed previously and subsequently. A nematological analysis will be carried out before the next crop in order to assess the levels of the soil populations and thus to be able to choose, in full knowledge of the facts, measures proportionate to the risks incurred.

As nematodes are soil-borne pests, the various measures recommended to control them will aim to limit, or even reduce, soil population levels.

Thus, crop rotations and certain cover crops are frequently recommended to delay the appearance of nematodes or to manage population levels in the soil. Rotations are not always easy to implement, in particular for certain polyphagous nematodes such as Meloidogyne spp. or Pratylenchus spp. Indeed, it is not always easy to find non-host plants that can enter the rotations. To be effective, these should last at least four years. Several crop and cover plants are reported to be, to varying degrees, less conducive to the development of Meloidogyne spp. : soybean, onion, garlic, corn, winter cereals, peanuts, arugula, Paspalum notatum, Cynodon dactylon, Eragrostis curvula, Chloris gayana, Digitaria decumbens, Panicum maximum, Crotalaria spp., Mucuna pruriens , sesame, genotypes resistant to nematodes of Vigna unguiculata … In Martinique, short rotations with the forage legume Mucuna pruriens made it possible to reduce the levels of populations of M. incognita and Rotylenchulus reniformis in the soil. Fallowing is sometimes recommended, but it poses erosion problems. In this case, it will be advisable to work the soil superficially several times during the year.

Nematodes are sometimes combated by immersing future plots that are already contaminated for 7 to 9 months. This immersion can be continuous or interspersed with periods of drying out of the soil. Under these conditions, the latter is depleted in oxygen and accumulates toxic substances for nematodes such as organic acids, methane ... This method is only effective if it is carried out at a hot period of the year, and includes the risk of spreading the nematodes at the same time. Weeds will be destroyed gradually by working the soil superficially at regular intervals.

Several plowing , early planting and mounds are sometimes recommended to limit the effects of nematodes. It is the same for the use of large clods to make the plants; in particular, they make it possible to delay infestations. It should be noted that the tools used for working the soil on contaminated plots must be thoroughly cleaned before being used in 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 soil and nematodes contaminating it.

Burying certain in the ground composts or green manures just before setting up a tomato crop can also help limit nematode damage. For example, compost made from coffee pulp would reduce the number of galls and egg masses of M. incognita . The same is true for cakes made from Azadirachta indica, Chrysanthemum coronarium, Ricinus communis, Sorghum sudanense , rye and oats. The contribution of organic matter to the soil (compost, manure) makes it possible to increase its water capacity, which would favor certain micro-organisms which enter into competition with nematodes.

Let us point out that the contribution of chitin to the ground would present a certain effectiveness against M. hapla .

In addition, weeds must be perfectly controlled in future plots because a certain number of them are liable to harbor and multiply nematodes. It will be advisable to perfectly control the fertilization of the plants as well as their irrigation.

It will be essential to obtain healthy plants . They will preferably be produced on tablets and in a disinfected substrate. They can be placed on the ground provided that the latter is covered with a clean plastic mulch and not torn. If you have any doubts about the quality of the soil in your nursery, you will need to disinfect it. In areas of extensive production, nurseries will not be set up on plots that have received sensitive plants.

Several nematicide products * have been and still are used to destroy nematodes in soils ( e-Phy ). Their choice will depend on the pesticide legislation in force in your country and the financial means available to you to carry out this disinfection. The use of these products has several drawbacks: many of them are toxic for humans and the environment, they are little or not specific and upset the biological balance of the soil and they are expensive and sometimes require specific equipment. . In some countries, they are used as a last resort, when the other methods proposed are no longer sufficient to effectively limit the damage of nematodes.

In countries where there is a lot of sunshine, disinfection of the soil by solarization could be considered, in particular to clean up the plots at a lower cost. This technique consists of covering the soil to be disinfected, which will have been well prepared and well moistened beforehand, with a polyethylene film 35 to 50 µm thick. The latter will be kept in place for 4 to 8 weeks during a very sunny period of the year. It increases the temperature of the soil and promotes the activity of microbial antagonisms. This helps to reduce the rate of inoculum in the soil of many phytopathogenic microorganisms, and in particular of certain nematodes. Many of them are removed at temperatures between 44 and 48 ° C. The use of nematicides and composts is sometimes associated with solarization to increase its effectiveness, in particular on Meloidogyne spp.

Whatever method is used to disinfect the soil, it is often recommended to implement it after harvesting, as many nematodes are still present in the superficial horizons. In addition, it will not be desirable to work the soil too deeply after disinfection, at the risk of bringing up uninfected soil.

Of resistant varieties are currently available. Resistance to Meloidogyne spp. comes from the wild species Lycopersicon peruvianum . It is conferred by a single dominant gene named " Mi " (now named " Mi-1 ") and results in a cellular hypersensitivity reaction at the site of nematode penetration: the larvae can no longer attach themselves to the root. and complete their cycle. This gene, located on chromosome 6, makes it possible to control 3 of the most common species: M. incognita, M. arenaria and M. javanica . Unfortunately, this resistance is not effective against M. hapla , which however sees its reproduction rate reduced on plants possessing the “ gene Mi ” . It is also not in respect of M. mayaguensis .

Virulent biotypes with regard to the “ gene Mi ” of the 3 species concerned by resistance have been described in many production regions: California, Japan, Morocco, Spain, Greece, France, etc.). It should be noted that these virulent populations are sometimes separated into two groups:
- selected virulent populations, coming from plots where resistant varieties have been cultivated several times. The virulence would be acquired gradually and stable; it would involve several genes in these nematodes;
- natural virulent populations (called “races B”), not recently confronted with resistant varieties.

It has been suggested that the genetic mechanism of the virulence of the first populations would be identical in the 3 species of Meloidogyne , but different from the natural virulent populations.

By way of example, let us point out that breeds capable of bypassing the “ gene Mi ” have been demonstrated in several countries in Europe and the Mediterranean Basin: in M. javanica in Spain, Greece, Crete, Cyprus, in Morocco, Tunisia, etc., and at M. incognita in France, Greece…. It should also be noted that races B of M. incognita have been described in Ivory Coast, and of M. arenaria in Senegal.

Despite this, the “ gene Mi ” , used for over fifty years, is still effective in many agronomic contexts. Note that the reproduction of M. incognita on genotypes having " Mi " in the heterozygous state would be greater than on genotypes having this gene in the homozygous state; this could have consequences on the durability of the resistance conferred by this gene. In addition, different levels of efficacy have been reported from time to time between resistant parents and their hybrids, possibly due to incomplete transfer of the “ gene Mi ” during crossbreeding. Finally, let us add that this resistance can also be overcome in the presence of high temperatures, of the order of 28 ° C and more.

These different findings suggest at least two tips:
- we should avoid cultivating a resistant variety or a rootstock on the same land for several years because there is a risk of adaptation of these nematodes;
- if a loss of effectiveness of resistance to nematodes is observed, it will be necessary to take stock with your technician in order to know if you are dealing with a strain capable of bypassing this resistance, with a species such as M. hapla not concerned by the latter or to drops in efficiency linked, for example, to high temperatures.

The emergence of virulent strains and the limits of the resistance conferred by " Mi " to high temperatures justified the search for other resistance to root-knot nematodes. Thus, 7 genes for resistance to Meloidogyne spp., Designated “ Mi-2 ” to “ Mi-8 ”, have been identified in accessions of Lycopersicon peruvianum and one in L. chilense . They confer resistances different from that conferred by the “ gene Mi ” . Some are effective against M. hapla and / or are still functional at 33 ° C. Thus, " Mi-2 " and " Mi-6 " would confer resistance to M. incognita at 32 ° C, " Mi-3 " to virulent isolates of the latter species, " Mi-4 " and " Mi-5 " to M. incognita and M. javanica at 32 ° C, " Mi-7 " to virulent isolates of M. incognita at 25 ° C as " Mi-8 ". resistance to M. hapla Heat-stable was observed both in an accession of L. peruvianum , but also in L. chilense .

The crossing between L. esculentum and L. peruvianum being difficult, the future of these genes remains uncertain.

Furthermore, a certain number of nematode and nematicide trap plants exist, such as, for example, Tagetes spp. ( T. erecta, T. patula …) which are nevertheless hosts in particular of M. hapla . These plants are still little used in the context of rotations with the tomato.

A number , parasites, nematodes of predatory microorganisms of gall nematodes have been tested on various plants: fungi such as Arthrobotrys irregularis, A. dactyloides, A. conoides, Glomus fasciculatum, Hirsutella minnesotensis, Paecilomyces marquandii or P. lilacinus , but also bacteria such as Bacillus penetrans, B. thuringiensis or Streptomyces costaricains … For example, Verticillium chlamydosporium infects the second larval stage and of eggs M. hapla .

Enfin, plusieurs Letting of automation (feuilles or roots) perturberaient le développement des nematodes notamment Wales: Azadirachta indica Chromolaena odorata, Deris elliptica, Euphorbia antiquities, Inula viscose, Peganum harmala, Ruta graveolens, Senecio cineraria, Swietenia mahagoni ...