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

Sour rot.

peduncles and frames, as well as adjacent parts of shoots, turn pitch black. Black discolourations of this nature are not to be confused with soot mould (which flourishes during the growing season on the honeydew of mealybug) – especially where they occur on trunks and parts of the cordon (Photos 98 & 99). It can be verified by pulling apart black coloured, loose parts of the bark during winter to ascertain the presence of hibernating mealybugs, should these be present.

PHOTO 88. A typical example of grey rot being arrested at an early stage to contribute to the ingress of sour rot (as a result of an initial wound).

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