- During cultivation

In the nursery , it is necessary to limit irrigations if they have been too abundant and to promote the ventilation of the shelters as much as possible. It is also urgent to impregnate the entire substrate with an anti-oomycete fungicidal solution. Diseased seedlings and those nearby must be eliminated (consult the recommended hygiene and disinfection measures ).

During cultivation and following root attacks, phytosanitary interventions are different depending on the context:
- in soil, generally few plants are affected and no treatment is to be applied;
- above ground, fungicides can be added to the nutrient solution. The doses chosen must be lower in order to avoid phytotoxicity.

Leaf attacks are normally well controlled by anti-mildew foliar treatments.

The range of fungicides * that can be used to combat oomycetes varies according to the type of salad and the target organ (table below).
 

 
The also be controlled climate of the greenhouse should in order to avoid excess humidity. For this, the shelters will be well ventilated. Good wiping of the soil should be favored after sprinkler irrigation and open field rains. We will maintain a fertilization balanced and we will avoid stressing the plants. Diseased plants and plant debris should be carefully removed, especially root systems.


- Next crop

A healthy or disinfected substrate should be used to produce the plants. In countries where producers make it themselves, for example from sand, reclaimed earth, various composts, there is a risk of contamination. The same will apply to producers who mix their purchased substrate with the aforementioned ingredients. The clods will not be placed on the ground, especially if it has not been disinfected. It will be best to place them on plastic wrap or shelves. In contaminated soils that have not been disinfected, the seedbed can be pre-emptively soaked with an anti-oomycetes fungicide solution. In France, it is recommended to incorporate propamocarb HCl into the soil or to soak the clods with it. The latter option may involve cryptonol. The hygiene measures recommended in the nursery can be implemented.

In some particularly affected soils, disinfection with a fumigant will be considered. Those which are conventionally used (propamocarb, dazomet, metam sodium applied alone or combined with dimethyl polysiloxane) ( e-phy ) are effective with regard to Pythium spp .. The same is true for steam . In production areas where it can be applied, solar disinfection of the soil (solarization) will be carried out. Quite spectacular results have been recorded, especially in certain Mediterranean countries. It consists of covering the floor to be disinfected, which will have been very well prepared and moistened beforehand, with a polyethylene film 35 to 50 µm thick. This will be kept in place for at least a month at a very sunny time of the year. It is an economical method, with a broad spectrum of efficiency, which makes it possible to control oomycetes.

The soil heavy and wet will be drained. Of crop rotations will be made with cereals and forage grasses. We will plant the salads on hillocks. This will prevent water retention at the foot of the plants. Fertilization should be balanced.

In some countries the seeds are coated with an anti-oomycete fungicide.

When planting, avoid planting plants in soils that are too wet or too cold; the irrigations carried out at this stage of the crop should not be too excessive.

In soilless cultivation, beware of the sanitary quality of irrigation water that comes from canals or basins that may have been contaminated. Disinfection of the nutrient solution may be considered. "Low pressure UV" units have been shown to be effective against Pythium spp. and Olpidium virulentus (ex Olpidium brassicae ) in various countries, in particular in Belgium, reducing the level of damage caused by these microorganisms. Other methods are currently being implemented to treat the nutrient solutions recycled from many crops: biofiltration, chlorination, etc. Their efficiency spectrum is wide and includes several fungi and in particular oomycetes.

There is no such thing as a resistant variety .

For information, certain microorganisms antagonistic have been tested to control some species of Pythium ( Coniothyrium minutans , Trichoderma harzianum , Trichoderma koningii , Gliocladium virens , Bacillus subtilis , Enterobacter cloacae , Burkholderia cepacia, etc.). Their use is already effective in some countries.


* As the number of pesticides available for a given use is constantly changing, we have nevertheless chosen to indicate in each sheet the name of a few active ingredients approved at the time of writing. We will try to update this list, as withdrawals and new approvals occur. Despite this, 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.