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

Oidium.

PHOTO 18. Spots as in Photo 17 become darker in colour when rubbed. A similar situation is encountered on petioles.

PHOTO 19. Oidium spots on slightly older shoots. One can almost be certain that when such infections are present, buds will also be affected.

A Guide to Grapevine Abnormalities in South Africa • 21