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

PART 2

and long term are seriously undermined. Total or partial die-off can thus occur in all viticultural areas in young as well as older plants. With reference to studies above ground, such die-off is associated with specific fungal diseases – which can occur singly or within a complex – and pruning wounds can/may be singled out as prominent entry points regarding initial infections. Thus the development cycle of various pathogens is launched to contribute to decay and/or blockage of vascular tissue, by which normal sap flow is of course seriously hampered and can even be halted. In the abovementioned regard leading research is currently being undertaken by both the Department of Plant Pathology (Stellenbosch University) and ARC Infruitec-Nietvoorbij (Stellenbosch) in which a number of overall aspects of especially the vine trunk disease complex are being unravelled. Emerging from this research a number of informative and industry applicable actions have already appeared in published format in which among others specific protocols could be laid down regarding: (i) the management of Eutypa die- back in South African vineyards (Halleen, 2010a) and (ii) the application of sanitary measures at nurseries to combat vine trunk pathogens (Halleen, 2010b). Contributions regarding the protection of pruning wounds against trunk infections – with inclusion of the application of Trichoderma products for biological control – could be considered extremely valuable for application in the local industry (Mutawila et al., 2011a, b). As vine dieback – which often varies in visual appearance - can be ascribed to individual or various pathogens within the trunk disease complex, the in-vineyard identification thereof is accordingly more complicated. Against this background, producers are strongly encouraged to immediately consult with experts at the abovementioned institutions (who have effective functioning disease clinics) in all cases of uncertainty concerning specific fungal diseases/problem situations, even if not exclusively applicable to fungal diseases. In this way actual causes can by accurately revealed, to ensure that suitable control and/or combating/ prevention strategies are implemented as speedily as possible.

A Guide to Grapevine Abnormalities in South Africa • 15