Protection methods

- During cultivation

There is no curative protection method to effectively control the tomato ( yellow leaf curl virus Tomato yellow leaf curl virus , TYLCV) during cultivation. Usually, an infected plant will remain infected for the rest of its life. In the event of the appearance of suspicious symptoms in a crop, we advise you to have a few diseased plants examined by a specialized laboratory which will carry out tests (Elisa, PCR) in order to confirm your diagnosis.

If the number of diseased plants in the crop is limited, we advise you to eliminate them quickly. It is also necessary to control the populations of whiteflies and therefore to carry out insecticide treatments * ( e-Phy ). Although they are not always very effective, they can somewhat limit the development of this virus.

If you carry out your production under cover, we recommend that you quickly make the latter proof against insects. For this, you can block the openings with nets insect-proof , non-woven sails of the P17 type for example.

At the end of the culture, the diseased plants will be eliminated quickly and not left in place as can be seen in some greenhouses. This will prevent the vector whiteflies from multiplying there and posing a danger to nurseries or future crops.

It will also be wise to create a crawl space of a few weeks under shelter. If you do not have this time, the uprooting of tomatoes will be preceded by insecticide treatments in order to reduce pest populations.


- Next crop

It should be remembered that TYLCV, like all Begomoviruses transmitted by Bemisia tabaci , is subject to European regulatory provisions (directive 92/103 / EEC of 1 December 1992, order of 2 September 1993). These stipulate in particular that all tomato plants sold to producers and originating in areas recognized as contaminated by TYLCV must be accompanied by a phytosanitary passport.

If you buy your plants, we recommend that you check their quality. Any suspect plant should also be destroyed. Indeed, the introduction of tomato plants infected with TYLCV represents a significant risk, in particular in production areas, or even in countries where the virus is not yet present. The control should concern both the appearance of the plants and the presence of potentially vector whiteflies. Bemisia tabaci parasitizes many vegetable and ornamental species, vigilance is essential when introducing them to a farm.

In countries where contamination is very early, nurseries and young plants will be protected, including during their transport and storage before planting, thanks for example to agro-textiles (non-woven sails, mesh fabrics etc.): the mechanical barrier thus created will delay contamination. The openings and entrances to the shelters will be made insect-proof . Double door systems with ventilation providing overpressure will therefore be preferable. Of preventive insecticide treatments * will be made ( e-Phy ), and may use biological control. We should add that it will be desirable for nurseries to be located far from production areas.

Sticky yellow signs placed in shelters and checked weekly will provide information on potential infestation pressure, provided there are virus reservoir plants nearby.

Careful weeding of nurseries, plots and their surroundings (edges of hedges and paths ) will be carried out in order to eliminate plants that are sources of viruses and / or vectors. The establishment of a nursery or a tomato crop near tomato productions already affected by TYLCV will be prohibited. Whenever possible, the establishment of tomato crops should be done at a time when whitefly populations are low. The first diseased plants will be eliminated quickly.

Resistance to TYLCV, certainly polygenic, has been demonstrated in several accessions of wild species close to tomatoes. They have been worked on for ten years by breeders. Thus tolerances have been observed and introduced into the tomato from several species of Lycopersicon , in particular L. pimpinellifolium, L. hirsutum, L. peruvianum, L. chilense .

Other resistance to Bemisia tabaci has been sought in several species of Lycopersicon . Various accessions are of interest, in particular because of the density of the glandular trichomes and various exudates which interfere with the whiteflies before they have transmitted the virus, for example by interfering with oviposition. On the other hand, the acquisition and transmission of TYLCV by Bemisia tabaci would then be reduced.

F1 hybrids tolerant to TYLCV have recently been marketed. The origin of their partial resistance is not specified, and we cannot guarantee that it is effective against the various Begomoviruses described. The choice is still limited for crops under cover, but it is expected to expand rapidly. For many tropical regions, breeders attempt to associate resistance to TYLCV with resistance to bacterial wilt. In more temperate zones, several resistant varieties are now available.

* 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.