Protection methods

- During cultivation

Unlike cryptogamic diseases, there is no curative control method allowing effective control of viruses during cultivation, and in particular against the cucumber ( mosaic virus Cucumber mosaic virus , CMV). Usually, an infected plant will remain so for its entire life, although the symptoms sometimes tend to subside.

If attacks take place in the nursery or during cultivation, and they are detected early, the few plants showing symptoms of this virus will be quickly eliminated and, for the plants, never planted subsequently. In fact, eliminating the plants infected virus with the at the very start of an epidemic can generally help to slow it down, or even to block it. But beware, the symptoms only expressing themselves a fortnight after infection of the plants, they, during incubation and therefore without apparent symptoms, may escape your observations and constitute a source of virus, and contribute to the development of the epidemic.

The treatments Aphicides * are often needed to control aphid populations on tomato. Unfortunately, they are not effective in preventing epidemics of viruses transmitted in the non-persistent mode. In fact, vector aphids frequently come from outside the plot and transmit the virus during brief bites, even before the aphicide has time to act. Moreover, the difficulties currently encountered in controlling aphids on tomatoes, sometimes linked to phenomena of resistance to insecticides, do not help to improve this situation.

A number of auxiliaries make it possible to control the population levels of aphids . Note that the proliferation of the latter leads to damage on tomato .

All weeds that can serve as a source of inoculum will be eliminated from the crop and its surroundings. This goal will sometimes be difficult to achieve given the large number of potential CMV hosts.


- Next crop

A set of measures should be implemented which will aim to prevent, or at least limit as much as possible, the introduction of the virus and its spread in tomato plots.

In countries where contamination is very early, it will be necessary to protect nurseries and young plants . For this, we can use agrotextiles (non-woven veils, mesh fabrics ). The mechanical barrier thus created will delay contamination. The greenhouses housing the plants will be made insect-proof . Yellow traps will be used to trap the first aphids, and thus be able to monitor changes in population levels and implement reasoned protection.

A weeding careful nurseries, plots and their surroundings (edges of hedges and paths ), will be made to eliminate sources of virus and / or vectors. It will be necessary to avoid setting up a tomato crop near crops more sensitive to CMV such as spinach, Cucurbitaceae Crop rotations may be considered in production areas where the pressure of the surrounding infected weeds is high.

A few sources of resistance to CMV, often partially effective, have been reported in several wild species of Lycopersicon :
- a dominant gene called “ cmr ” which would be located on chromosome 12 of L. chilense ;
- different accessions, including 3 in Lycopersicon esculentum , 2 in L. hirsutum , 1 in L. chmielewskii and L. pimpinellifolium . The effectiveness of these resistances seems to vary depending on the strain.

It should be remembered that in order to protect tomatoes against lethal necrosis, premunition tests were carried out in France with the CMV-R strain. This contains an RNA-5 which does not cause symptoms after mechanical inoculation. Greenhouse tests have shown that this strain offered effective protection against an aggressive strain. Comparable results have been obtained in different countries, with other strains containing an RNA-5. Field trials were even carried out: they showed that the percentage of plants showing symptoms of mosaic was significantly reduced.


* 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.