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Protection methods

- During cultivation

There is curative method no to fight the turnip ( mosaic virus Turnip mosaic virus , TuMV). An affected plant will remain so throughout its life.

Usually, the elimination of plants infected virus with the at the very beginning of an epidemic can help to slow it down, but the difficulty of observing characteristic symptoms in lettuce sometimes makes this practice illusory. In addition, since the symptoms do not appear until several days after contamination of the plants, the salads during incubation, and therefore undetectable, may already constitute a source of virus and participate in the development of the epidemic.

Of Aphicides treatments are essential to control outbreaks of some aphids on salads. They are generally ineffective in controlling the development of viral diseases. In fact, vector aphids frequently come from outside the plot and can transmit the virus even before the aphicide has time to act.

- 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 the lettuce 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 sails, mesh fabrics, etc.). The mechanical barrier thus created will delay contamination.

A weeding careful nurseries, plots and their surroundings (edges of hedges and paths ...) will be carried out to eliminate the sources of viruses and / or vectors. Mustard, rapeseed and rutabaga regrowth will be destroyed in nearby plots. It is necessary to avoid setting up a salad crop near crops more sensitive to TuMV, especially crops of various cabbages. Sensitive varieties should be avoided in areas particularly infested by weeds.

Considering the mode of transmission of this virus and the large number of potentially infected plant species, the use of resistant varieties is the necessary control method. Several types of resistance (immunity, tolerance and reduced susceptibility to infection) have been described in lettuce. Resistance to the virus is conferred by a dominant gene called " Tu ". It appears that the vast majority of buttered and romaine lettuce varieties have extreme resistance to TuMV.

It should be noted that the susceptibility to this virus may be closely linked to a gene for resistance to late blight ( gene Dm 5/8 ), isolated from a particular accession of Lactuca serriola . In the past, when breeding older batavia iceberg lettuce varieties, breeders lost resistance to TuMV at the same time as they introduced the gene Dm 5/8 for resistance to Bremia lactucae . We find the same situation in current American, European or French varieties resistant to mildew and widely cultivated even today.

NB: Controlling insect populations on a crop implies, depending on the situation, the use of insecticides. As the number of insecticides available for a given use is constantly changing, 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, materials. fertilizers and growing media approved in France. This also applies to all biological products based on microorganisms or natural substances.

Last change : 04/27/21