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Protection methods

- During cultivation

When you observe symptoms due to these two Sclerotinia spp . in your crop, if a preventive treatment program has not been set up, we recommend that you apply one of the fungicides * approved in France on crown rots of lettuce and escarole, curly : iprodione, pyrimethanil, cyprodinyl + fludioxonil, boscalid + pyraclostrobin, triturous sulfur, Bacillus subtilis (e-phy lettuce - escarole, curly ). As for witloof chicory (chicory production) , treatments based on iprodione are possible both in treatment of plants by spraying on the collar and soaking of the roots and in soil treatment . For witloof chicory (root production) , iprodione is recommended as a seed treatment . From this point on, it is necessary to follow the treatment schedule recommended below and to respect the pre-harvest periods (variable depending on the fungicides) (Note that only preventive treatments are really effective on neck rots in salads. ).

In addition, several prophylactic measures complementary to chemical control should be implemented. The shelters must be ventilated as much as possible, in order to reduce the ambient humidity and to avoid the presence of free water on the plants. The irrigations will preferably be carried out during the morning and at the beginning of the afternoon, never in the evening, in order to allow the plants to dry as quickly as possible. In some cases, it may be necessary to heat the shelters in order to reduce the humidity and in particular to eliminate the dew present on the leaves.

must be removed very quickly Plant debris during cultivation , especially affected plants on which these two fungi produce numerous sclerotia.

also be controlled Nitrogen fertilization will . It should be neither too excessive (at the origin of very receptive succulent tissues), nor too weak (sources of chlorotic leaves constituting ideal nutritional bases for them).

At the end of cultivation , the plant debris must be quickly removed from the plots and destroyed, in order to prevent them from being buried in the ground and that the fungi can remain there. It is also recommended to apply the preparation based on Coniothyrium minutans (Contans WG) on crop residues, this antagonist fungus destroys a certain number of sclerotia and contributes to reducing the inoculum pressure during the following culture.
In the absence of culture, the immersion of the infested plots makes it possible to reduce the number of viable sclerotia present in the soil.

- Next crop

In the event that the nurseries will be carried out each year in the same shelter, it will be essential to put in place the recommended hygiene and disinfection measures .

The efficiency of crop rotations is quite disappointing; this situation is certainly due to the polyphagia of these two Sclerotinia spp. Rotations of at least 5 years should be carried out in heavily contaminated soils. It will be in your best interest to alternate salad crops with cereals. It should nevertheless be noted that the cultivation of broccoli cabbage, alternating with salads, and the burying of the residues of this plant, allow the USA to reduce the number of sclerotia in the soil and the damage caused by Sclerotinia minor . In this country, it is also considered that corn, cereals, onions, spinach are not conducive to the development of these two Sclerotinia . Green manures sensitive to these fungi should not be grown either, although some organic amendments reduce the damage of Sclerotinia sclerotiorum .

Repeated cultivation of plants susceptible to one or both Sclerotinia spp. on the same plots will inexorably lead to an increase in soil inoculum. In this case, several control means can be considered preventively to control these fungi. Some will aim to reduce the rate of surface inoculum in the soil. This will be the case in particular for soil disinfection methods *. Several fumigants can be used (dazomet, Coniothyrium minitans , metam-sodium alone or combined with dimethyl polysiloxane) ( e-phy ). You should know that these fumigants are more or less effective, some of them pose material problems and cause a number of disadvantages:
- destruction of natural microorganisms antagonists of certain pathogenic agents;
- increased receptivity to parasites in disinfected soil;
- appearance of toxicity phenomena (excess of exchangeable manganese, excess ammonia following a more or less complete blockage of nitrification, etc.).

In sunny regions, solar energy will also be used. The solar disinfection of the soil (solarization or pasteurization) is increasingly implemented in many countries and now in France. 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 is kept in place for at least a month, this at a very sunny period of the year. It is an economical, efficient method, which will make it possible to control the colonizing fungi of the superficial zone of the soil.
The soil can also be disinfected with steam. There are now machines better suited to market gardening; there are automatic machines for large surfaces to be disinfected.
In non-disinfected soil, the preparation based on Conithyrium minutans ( Contans WG) may be used.

The soil of future salad plots will be well prepared and drained in order to avoid the formation of puddles conducive to late attacks after heading and the formation of apothecia responsible for aerial contaminations of Sclerotinia sclerotiorum . The deep plowing will bury the sclerotia in depth and will be quickly destroyed by terrestrial microorganisms antagonists. In the open field, the rows of planting will be oriented in the direction of the prevailing winds so that the collar of the plants and the vegetation cover are well ventilated. The planting of salads on mounds also promote aeration of their collar and avoid stagnation of water in the vicinity. The use of plastic mulch will partially isolate the old leaves from the soil and therefore help reduce contamination of at least the two Sclerotinia spp. and Rhizoctonia solani .

Of preventive fungicide treatments may be carried out after planting. We can use the same schedule of treatments as that recommended for Botrytis cinerea . Thus, 3 to 5 applications will be positioned just after planting (especially for Sclerotinia minor ) and at stages 7-9 and 11-13, in order to be able to reach the old leaves before the salads cover the ground. Their number will fluctuate depending on the time of year, the type of salad, the type of crop (open field and under cover) and production areas. The products mentioned above can be used.

The other diseases and pests must be controlled because they are the cause of wounds, tissue necrosis conducive to the installation of these two fungi. As soon as the vegetation becomes important, it will be necessary to be vigilant, especially in period of cloudy weather and when the salad head approaches.

The irrigations should preferably be carried out in the morning and at the beginning of the afternoon, never in the evening, in order to allow the plants to dry as quickly as possible. They will never be excessive and should not permanently maintain a surface humidity of the soil. We should be wary of watering carried out near the harvest because the conditions (presence of water, great receptivity of the plants, etc.) are very conducive to these mycoses. Experimenters report that localized irrigation combined with shallow plowing would reduce the damage caused by Sclerotinia minor , compared to furrow irrigation occurring after conventional plowing.

Although no varietal resistance was found in lettuce, differences in susceptibility were observed between cultivars, especially against Sclerotinia sclerotiorum .

For information, several fungi and antagonist bacteria have been evaluated in vitro or in vivo to control them. Among them, mention may be made of: Streptomyces griseoviridis , Coniothyrium minutans , Gliocladium virens , Sporodesmium sclerotivorum , Talaromyces flavus and Trichoderma harzianum .

* 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.

Last change : 04/26/21