A Guide to Grapevine Abnormalities in South Africa - P.G. GOUSSARD

Botrytis (grey rot).

the vines until late in the season. Such berries lose moisture through evaporation, change colour from light to golden brown, shrivel and gradually change into a kind of soft raisin with exceptionally high sugar concentrations (Photos 82 & 83). In South Africa – especially in years with dry autumn periods – excellent late harvest wines associated with noble rot have often been made. Where conditions are not favourable, however, it is not unusual for bunches on the vine to be totally covered in rotting nests and spores, often with the added presence of other harmful secondary rotting organisms (Photos 84 & 85). The presence of honey bees during late autumn (when sour rot is finished and the above- mentioned organisms are present), is often indicative of noble rot berries somewhere in those bunches (Photo 86). Botrytis can also affect leaves and shoots and cause significant damage, although this seldom occurs locally, except under intensive conditions, for example hothouses and plastic-covered tunnels used for callusing purposes (Photo 87).

PHOTO 73. Light brown skin discolourations accompanied by “glyskil” after infection are characteristic of grey rot. This wound, caused by a pecking bird, was used as a port of entry by germinating fungal spores to penetrate the berry.

54 • A Guide to Grapevine Abnormalities in South Africa