The grape berry is affected by numerous pests and diseases: insects , but also several dozen microorganisms present in the majority of grapevine production areas in the world. These microorganisms responsible for alterations in grape berries can be dissociated into two behavioral groups (figure 1).

Figure 1

 

  

Their number is limited, and they appear mainly before veraison: Erysiphe necator ( powdery mildew ), Guignardia bidwellii ( black rot ), Phomopsis viticola ( excoriose ) and a chromist (or stramenopile) Plasmopara viticola ( downy mildew ). These microorganisms are fairly well known to wine growers; they also affect other organs of the grapevine, in particular the leaves and herbaceous branches. Let us also add to this group, Pilidiella diplodiella white burp agent;

 

They are much more numerous and less well known to wine producers. They only become pathogenic on berries that are overripe and / or injured, and / or already colonized by a first invader (mainly Botrytis cinerea ): Alternaria spp. ,  Aspergillus spp. , Aureobasidium pullulans , Cladosporium herbarum , Penicillium spp. ,  Rhizopus stolonifer , Trichothecium roseum, etc.  It should be noted that many of these fungi seem to be predominant on bunches of grapes harvested in wine-growing areas of several countries, whether on table or wine grapes .

This sheet only concerns the fungi of the second group, also excluding the microorganisms responsible for acid rot and gray rot ( Botrytis cinerea ). Remember that the latter can be classified in the two behavioral groups since it is able to attack both inflorescences and green berries as well as those having reached an advanced stage of maturity.

These rots are responsible in some years for qualitative and quantitative losses during the harvest, which are sometimes considerable. During their development on berries, several of them are liable to produce mycotoxins and / or unfavorable aromatic compounds which impair the health and / or organoleptic qualities of wines. Note that the nature of the microflora in grapes can be influenced by several factors: grape variety, climatic conditions, soil, cultivation practices, geographic location.