Biology, epidemiology

The Cladosporium spp. possess biological characteristics comparable to those of other opportunistic fungi on grape berries. They often live as saprophytes on the vine and its environment, becoming opportunistic pathogens when the physiological state of the berries is modified (presence of wounds, advanced maturity ...).

• Storage and sources of inoculum

Cladosporium spp. are considered the most common molds in the world, found in the soil as well as on the most diverse hosts and substrates. It is therefore not surprising to observe them on the vines and the grape berries in the various vineyards. C ladosporium herbarum has saprophytic potentials allowing it to easily maintain itself in the mycelial state in plant debris, on bark or vine shoots, in dead vines. It is also part of the natural flora of this plant species. This fungus is also found on many plants which ensure its conservation and multiplication.

• Host penetration and invasion

This fungus penetrates berries mainly when ripe, at least in 2 ways:

- directly through the cuticle in the presence of exudates;
- through the stomata, lenticels and microcracks, various injuries such as damage linked to pathogenic insects or fungi, physiological micro-bursts, bird pecks or solar burns.

Subsequently, the mycelium grows very extensively, growing in all directions inside the flesh which gradually degrades.

• Sporulation and dissemination of the fungus

C. herbarum sporulates quite easily on the surface of berries (Figures 1 and 2) and the conidia are dispersed by drafts and / or splashing water following rains.

• Factors influencing development

The thermal optimum for the development of C. herbarum is between 20 and 25 ° C, but this fungus can evolve at temperatures between 4 and 30 ° C. It still grows slowly at 0 ° C and thus poses problems for table grapes stored in the cold. It is typically a pathogen of fruits harvested late and stored.