Gray mould rot (Botrytis cinerea) is one of the most important pathogens of grapes, which can infect all green parts of the plant, but is most dangerous on the bunches. It is a highly polyphagous (polyphytic) pathogen.

This fungus overwinters on dead tissues with mycelia or sclerotia, so that the infective material is virtually always present in the vineyards. Under favourable conditions it can also become a parasite and infect the green parts of the vine. It is important to note that it is most easily infected through wounds and injuries, but it can also enter the plant through healthy plant parts.

Warm, wet weather is favourable for the pathogen. In the spring, conidia (asexual reproductive cells) developing from sclerotia overwintering on dead plant parts are carried by the wind to susceptible green parts of the vine and infection occurs under optimum conditions. (The sclerotium is a compacted tissue of hyphae, consisting of a hard, dark outer bark and a lighter inner layer.) The conidia persist throughout the growing season, can be a source of mass infection and are drought tolerant.

In the spring, the first symptoms may appear in the form of rapidly growing, irregular necrotic spots on the leaves starting from the main vein during wet, humid periods.
Protection against it requires great care by all vine growers.

Havasi Máté
plant health specialist
PlantCT Europe Zrt.