Risk factors

Botrytis cinerea is a very polyphagous fungus which can colonize hundreds of cultivated plants or weeds that contribute to its conservation and are potential sources of inoculum. Due to its saprophytic ability, the fungus can survive  on the organic matter in the soil as mycelium or sclerotia, these latter surviving several years in the soil and on plant debris. On all its hosts as on plant debris, the fungus produces a grey mould formed by a mycelium and many long and branched conidiophores bearing at their ends spherical to ovoid conidia which ensure the dissemination of B. cinerea. Sporulation can begin 3 days after the first contamination. The dissemination is carried out mainly through the wind and to a lesser degree through the rain and splashing water. The spores germinate on the leaves within a few hours in the presence of high humidity.

Botrytis cinerea is particularly favored by wet environments and the optimal conditions for its development are a relative humidity around 95% and temperatures between 17 and 23 ° C. These conditions can be found in the field during rainy periods or as a result of irrigation by aspersion. The weakened or or etiolated plants are particularly vulnerable. Sometimes, the withered flowers serve as starting point for the development of the disease. Low light intensity promotes the development of grey mould and botrytis is especially a problem when the light intensity is low.

Some potato varieties are more sensitive than others to grey mould.