• Logo_picleg
  • Quae

Protection methods

- During cultivation

The fight against Botrytis cinerea is always rather delicate on salad ; several explanations can be given for this situation:
- plants particularly receptive (succulent and tender leaves), often cultivated in a climatic context favorable to Botrytis cinerea , in particular under shelters;
- an obligation to stop treatments fungicide relatively long before harvesting , in particular at a time when lettuce is most vulnerable;
- a particular aptitude of this fungus to adapt quickly to the fungicides which are opposed to it;
- too few fungicides registered for the "crown rot" use of lettuce.

When you observe symptoms of Botrytis cinerea in your crop and if a preventive treatment program has not been set up, we advise you to carry out an application with one of the fungicides * approved in France: iprodione R , pyrimethanil R , cyprodinyl R + fludioxonil, boscalid + pyraclostrobin, triturating sulfur, Bacillus subtilis ( e-phy lettuce - escarole, curly ). From this point on, it is necessary to follow the treatment schedule recommended below and to respect the pre-harvest periods, which vary according to the fungicides (Note that only preventive treatments are really effective on crown rots in seedlings. salads). Given the small number of active ingredients available for this use and the number of modes of action, it is very difficult to organize one or more anti-resistance strategies. We should add that the recent approval of the boscalid + pyraclostrobin combination significantly improves the situation.
( R : resistance to this product known in B. cinerea )
(Remember that the use of pyrimethanil and cyprodinil + fludioxonil are not without risk of phytotoxicity, in particular in greenhouses)

In addition, several prophylactic measures complementary to chemical control should be implemented, both in the nursery and in the field. The shelters must be ventilated as much as possible, in order to reduce the ambient humidity and, in particular, to avoid the presence of free water on the plants . The installation of a heat shield on the salads, such as an agro-textile (non-woven veil, mesh fabric), helps to increase humidity and decrease luminosity. In the case of severe attacks, it is better to remove it. It is advisable to carry out the irrigations 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 Botrytis cinerea sporulates abundantly and sometimes forms sclerotia. We will avoid any stress to the plants leading to spurts of growth.

The nitrogen fertilizer should be controlled . It must be neither too excessive (at the origin of very receptive succulent tissues), nor too weak (sources of chlorotic leaves constituting ideal nutritional bases for Botrytis cinerea ).

At the end of cultivation , plant debris must be quickly removed from the plots in order to prevent them from being buried in the ground and that the fungus can remain there. Deep plowing will facilitate the decomposition of the few remaining residues.

- Next crop

If the nursery will be carried out each year in the same place and / or in the same shelter, it will be essential to put in place the recommended hygiene and disinfection measures .

The efficiency of crop rotations is disappointing; this situation is certainly due to the polyphagia of Botrytis cinerea and to the fact that the inoculum largely comes from the environment of the culture.

The soil of the future plots salad will be well prepared and drained in order to avoid the formation of puddles conducive to late attacks after heading. In the open field, the rows of planting should be oriented if possible in the direction of the prevailing winds so that the crown of the plants and the vegetation cover are well ventilated. Planting salads on hillocks also allows aeration of their necks and prevents water stagnation near them. Too high planting densities and to injure the plants should be avoided.

Of preventive fungicide treatments will be needed. Currently, the calendars offered in France and in many other countries are roughly comparable. They involve 3 to 5 treatments in addition to those carried out in the nursery (often positioned after planting, at stages 7-9 and 11-13). Their number fluctuates depending on the time of year, the type of salad, the type of crop (open field or under cover) and production areas.

Other diseases and pests must be controlled because they are the cause of wounds and tissue necrosis conducive to the establishment of Botrytis cinerea . Tip-burn symptoms should be avoided for the same reasons. 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.

Although no varietal resistance was found in lettuce, as in many other hosts of this fungus, slight differences in susceptibility are observed between cultivars. They are linked to the more or less erect ports of certain types (romaine, fat lettuce) or to a thicker leaf cuticle. In addition, chicory appear less sensitive than lettuce.

A number of original methods have been or are being tested in several countries. Thus, compost extracts have been used in England; sprayed on plants, they would reduce damage caused by Botrytis cinerea and increase yields. Antioxidants have also been used in Israel to limit the development of this fungus.

Several fungi and bacteria antagonistic have been evaluated in vitro or in vivo to control it. Among them, mention may be made of: Streptomyces spp. such as Streptomyces griseoviridis …, Gliocladium virens , Trichoderma harzianum , Ulocladium atrum ...

* 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 : 05/03/21