Protection methods

- During cultivation

No control method is really effective during cultivation on lettuce to control Meloidogyne spp. .

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

In the open field, it is imperative that the root systems of the attacked lettuce be removed from the plot and eliminated , to avoid enriching the soil with nematodes. When this last measure is not possible, we can put the roots in the open air so that they are subjected to the effects of the sun. In the same way, several successive plows, carried out during the summer, will help to expose the nematodes to heat and to kill them.


- Next crop

To be effective, the fight against root-knot nematodes must involve, in a complementary way, all the control methods proposed here.

The crop rotations are frequently advised to delay the onset of nematodes or limit their expansion. These 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 resistant plants that can enter rotations. To be effective, rotations should result in an absence of susceptible hosts on the plot for at least four years. In Martinique, short rotations with the forage legume Mucuna pruriens made it possible to reduce the populations of Meloidogyne incognita and Rotylenchus reniformis in the soil. The fallow is sometimes advocated in some countries, but it poses problems of soil erosion.

There are a certain number of "trap plants" for nematodes or "nematicides" ( Tagetes spp.: Tagetes erecta , Tagetes patula ...) which are still little used in the context of rotations with salads. Burying certain compost or green manure in the ground just before establishing a salad crop can also reduce nematode damage. For example, compost made from coffee pulp reduces the number of galls and egg masses of Meloidogyne incognita on lettuce. The same goes for oil cakes made from Azadirachta indica . Sorghum sudanense , rye and oats, gradually susceptible hosts to Meloidogyne hapla , are used as cover crops and green manure. The supply of chitin to the soil has a certain efficacy against Meloidogyne hapla .

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, it will need to be disinfected.
Several nematicide products can be used. 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.

List of active ingredients used in France to fight nematodes on crops, as well as some information about them:

The fumigants that can be used are 1,3-dichloropropene, dazomet, and metam sodium ( link 1 e-phy ) ( link 2 e-phy ). These are often quite versatile products in addition to being nematicides (fungicides, insecticides, herbicides). They are generally most effective in well-drained, porous soils. They act directly on nematodes. These products are mainly used in nurseries. They are more effective than non-fumigants. 1,3-Dichloropropene has a weak action on weeds. Dazomet and metam-sodium are seldom used. A number of them are used in the open field.

No non-fumigant product is currently registered for nematode use on salads.

Remember that the use of these products has several disadvantages:
- many of these products are toxic to humans and the environment;
- they are little or not specific and upset the biological balance;
- they are expensive and sometimes require specific equipment.

In countries where there is a lot of sunshine, solar disinfection of the soil (" solarization ") may 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 microns thick. The latter will be kept in place for at least one month, during a very sunny period of the year. It increases the temperature of the soil and promotes the activity of microbial antagonisms. This contributes to reducing the rate of inoculum in the soil of numerous phytopathogenic microorganisms and in particular of certain nematodes. The use of nematicides and composts ... is sometimes associated with solarization to increase its effectiveness on Meloidogyne spp. especially.

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 soil is depleted of 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 time of the year. It involves certain risks linked to the possibility of disseminating the nematodes at the same time.

Several plowing , planting early and on mounds , are recommended to limit the effects of nematodes. It is the same for the use of large clods to make the plants. Tools used for tillage of contaminated plots should be thoroughly cleaned before being used 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 soil and nematodes contaminating it.

Weeds should be perfectly controlled in future plots, as a number of them harbor and multiply nematodes.
It will be advisable to perfectly control the fertilization of the plants as well as their irrigation.

There seem to be some differences in susceptibility to Meloidogyne spp. in salads. In lettuce, differences in egg production were observed for Meloidogyne incognita race 1 and Meloidogyne javanica . Monogenic resistance to Meloidogyne incognita has been found in the lettuce cultivar "Grand rapids" in Brazil, Lactuca saligna and Lactuca dregeana have been shown to be resistant to a population of Meloidogyne hapla greenhouse .

A certain number of microorganisms parasitic of root-knot nematodes have been tested on lettuce: Paecilomyces marquandii , Verticillium chlamydosporium , Costa Rican Streptomyces , Bacillus thuringiensis ... For example, Verticillium chlamydosporium infects the second larval stage and eggs of Meloidogyne hapla .


NB: The legislation on pesticides evolving very quickly, we advise you to consult 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 culture media approved in France. This also applies to all biological products based on microorganisms or natural substances.