Protection methods

• During cultivation

When you observe symptoms due to an attack of Sclerotinia sclerotiorum  on the stem (collar or pruning wounds), on vegetation or on fruits in flat culture, a treatment with a fungicide can be carried out. The following active have been, and are still used in some countries: ingredients benomyl, thiram, iprodione, procymidone, vinchlozolin and its association with maneb , pyrimethanil, cyprodinyl + fludioxonil … Currently, only one fungicide is registered for this use on courgette in France ( e-phy ) *.

It should be noted that strains resistant to benzimidazoles (benomyl, carbendazim, etc.) and to quintozene have been reported in the literature. Also, it is advisable to alternate fungicides with different modes of action.

Several prophylactic measures must complement the chemical control in order to reduce the ambient humidity and avoid the presence of free water on the plants: aerate as much as possible and possibly heat the shelters, and irrigate preferably during the morning and at the beginning of the day. afternoon - never in the evening. Remember that localized irrigation is preferable to other irrigation methods.

The plant debris will be disposed of during cultivation, especially the affected plants on which the fungus produces numerous sclerotia, but also the end of culture to avoid their conservation in the ground after burial. Nitrogen fertilization will also be controlled. It should be neither too strong (at the origin of very receptive succulent tissues), nor too weak (sources of chlorotic leaves constituting nutrient bases).

• Next crop
  

If the nurseries are carried out each year in the same shelter, it is essential to put in place hygiene measures .

Note that in the absence of culture, immersion of infested plots would reduce the number of viable sclerotia present in the soil.

The efficiency of crop rotations is quite disappointing; this situation is certainly due to the polyphagia of this Sclerotinia . However, heavily contaminated soils justify such rotations, of at least 5 years. It will be in your best interest to alternate the cultures of zucchini and squash with, for example, cereals. In this country, it is considered that corn, cereals, onions, spinach are not conducive to the development of this Sclerotinia . Green manures susceptible to this fungus will also not enter the rotations, although some organic amendments reduce the damage of S. sclerotiorum .

Repeated cultivation of plants susceptible to S. sclerotiorum on the same plots will inexorably lead to an increase in soil inoculum. In this case, several preventive control means can be considered, such as soil disinfection . Several fumigants can be used ( e-phy ): dazomet, metam-sodium ... However effective they are, some of them nonetheless 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 production areas, solar disinfection of the soil ( solarization or pasteurization) can be implemented with some efficiency. It consists of covering the soil to be disinfected, which will have been carefully prepared and moistened beforehand, with a polyethylene film 35 to 50 µm thick, held in place for at least one month at a very sunny period of the year. This economical and efficient method will make it possible to control the colonizing fungi of the superficial soil zone.

The steam is also effective against this fungus.

The soil of future courgette and squash plots will be well worked and drained in order to avoid the formation of puddles, particularly conducive to the formation of apothecia responsible for aerial contaminations of S. sclerotiorum . Deep plowing will bury the sclerotia in depth, which will then be more quickly destroyed by antagonistic soil microorganisms. 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 use of plastic mulch will partially isolate the vegetation from the ground and therefore help reduce contamination. In addition, in some cases, it will help trap the ascospores released by the apothecia of S. sclerotiorum .

Of preventive fungicide treatments may be made in the case of very high inoculum pressure. Their number will fluctuate depending on the time of year, the type of crop (open field, under cover) and the production area. The products mentioned above can be used. Remember that currently, only one fungicide is approved for this use on zucchini in France ( e-phy ).

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. In the open field, abundant vegetation should lead to vigilance, especially in period of cloudy and wet weather.

To our knowledge, no resistance to this fungus has been reported on zucchini and squash.

Finally, it should be noted that several antagonist fungi and bacteria have been evaluated in vitro or in the field to control this Sclerotinia . : Streptomyces griseoviridis, Coniothyrium minutans, Gliocladium virens, Sporidesmium sclerotivorum, Talaromyces flavus, Trichoderma harzianum … We should add that Coniothyrium minutans is now approved for this use in France ( e-phy ).


* 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 products phytopharmaceuticals and their uses, fertilizers and growing media approved in France. This also applies to all biological products based on microorganisms or natural substances.