• During cultivation
  

If powdery mildew spots ( Podosphaera xanthi and Golovinomyces cichoracearum ) are observed on the plants, it is advisable to react quickly and to put in place a certain number of measures in order to reduce as much as possible the epidemic of the fungus (s) that may be raging. Note that it is always difficult to limit the development of this disease when it has started to manifest itself more or less in a culture.

It can be recommended to quickly eliminate the first attacked leaves, taking care to put them directly in a plastic bag in order to avoid spreading spores. Subsequently, they will be taken out of culture and destroyed.

The chemical control currently remains the most used method to control powdery mildew. Plants should be protected quickly with fungicides. Several active ingredients or combinations * of the latter are authorized for use in powdery mildew on zucchini ( e-phy ).

* The sprays will be neat and will take care to cover well the lower leaves and the underside of the blade. They will be renewed in alternating active ingredients with different modes of action because of the strains of these fungi less sensitive or r ésistantes several fungicides approved were reported. Treatments will not be carried out when the temperature is high because there is a risk of phytotoxicity with some of these products. One should also be wary of the repercussions that certain anti-powdery mildew active substances may have on some biological control agents used in greenhouses.

We also advise you to follow a number of hygiene measures throughout the cultivation:
- limit the presence of visitors in the greenhouse in order to reduce the risks of dissemination;
- gently remove the old leaves or strongly oidized leaves (to avoid the dispersion of spores as much as possible); this will eliminate a large part of the secondary inoculum and promote aeration and sunlight in the lower parts of the plants;
- control the climate of the shelters in order to reduce the relative humidity and promote air circulation. Water condensation on the foliage should be avoided. In addition, let us remember that the development of powdery mildew in Cucurbitaceae seems rather limited by temperatures above 35 ° C. Also, we may be interested in using this sensitivity to high heat to reduce its incidence in shelters, especially since these plants tolerate temperatures of 37 ° C - 38 ° C quite well a few hours a day, in particular zucchini. All the same, we should be careful not to promote the proliferation of mites;
- manage fertilization so as not to obtain plants with too excessive growth and leaves with too succulent tissues;
- eliminate weeds near crops and avoid the presence of clusters of waste in its environment.

Remember that spraying or misting water on plants is a method known for a very long time to control powdery mildew in crops. It should be done in the morning so that the plants have time to dry out and dry quickly so as not to promote other pathogens.

The plant debris will be disposed of fairly quickly crop, both during cultivation (following different cultivation operations) and late crop after the uprooting of plants. They will imperatively be destroyed.

• Next crop

First of all, remember that it will be wise to implement all the protection methods recommended above.

First of all, let us stress that it is always very important to create a crawl space between two crops sensitive to powdery mildew, especially in greenhouses. Indeed, the period of two to three weeks during which the greenhouse will be left empty will allow:
- prevent the fungi (s) responsible for powdery mildew from remaining in the shelter environment and therefore contaminating new plantations (powdery mildew conidia have a limited lifespan in the absence of a susceptible host );
- clean and disinfect thoroughly the shelter and the equipment used in it ( e-phy ).

We will try not to set up a new crop near sensitive crops, often already affected. The surroundings of crops and greenhouses should be cleared of weeds and clumps of crops potentially sources of inoculum.

be chosen Planting densities should to avoid the constitution of too dense a plant cover, favoring shade and reducing aeration. Watering and nitrogen fertilization should not be excessive.

We must pay attention to the quality of the plants ; in fact, it is not uncommon to find that certain plants sold are already contaminated when they arrive at the producers. It is advisable to check them on their arrival and to carry out a treatment if their quality is doubtful ( e-phy ). Note that a number of rootstocks are very sensitive to powdery mildew, so beware.


The treatments anti-mildew preventative can be made with different active ingredients ( e-phy ) and following the advice previously advocated.

Several champignons antagonistes de ces oïdiums ont été signalés dans la literature, Acremonium alternatum , Ampelomyces quisqualis , Aureobasidium pullulans , Pongo short , Bacillus brevis , Lecanicillium spp., Cryptococcus laurentii , Enterobacter cloacae , Lecanicillium longisporum , Paecilomyces fumosoroseus , Pseudozyma flocculosa (syn: Sporothrix flocculosa ), Rhodotorula glue , Saccharomyces cerevisiae , Stephanoascus sp. Tilletiopsis smaller , Verticillium lecanii ...
In France, none of them is currently used in practice in a declared way to biologically control the development of the two fungi responsible for powdery mildew. Some of the various preparations offered to professionals to "stimulate the growth of plants and sometimes protect them" must probably accommodate one or more of them.

It should be remembered that many plant extracts have also been tested to control in vitro or in the field G. cichoracearum or P. fulinigea . We quote a number as examples: Achyranthes japonica , Cassia . Spp Corydalis chaerophylla , Dalbergia hupeana , Euphorbia humifusa , Fallopia sachalinensis , Inula viscosa , Quillaja saponaria , Reynoutria sachalinensis , Rheum . Spp, Robinia pseudoacacia , curly dock , Styphnolobium japonicum , Verbascum eremobium …

For information, various products and preparations were evaluated in foliar sprays with regard to powdery mildew, this with more or less success: certain clays, silica, potassium bicarbonate, potassium iodide, monopotassium phosphate. , alginates, acibenzolar-S-methyl, O3 and sulfur dioxide, milk and milk-based preparations, enzymes (lactoperoxidase)…


* 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 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.