Symptoms and fungi associated with esca in South African vineyards

Abstract

In the past, only a few incidences of esca diseased grapevines were reported from the Slanghoekand Rawsonville areas of South Africa, with the damage believed to be of little importance so that the diseasehas not been studied in South Africa. In the present study, vines with internal or external symptoms of the esca disease complex were sampled from table, raisin and wine grape cultivars from 37 production areas inthe Western Cape, Northern Cape and Limpopo provinces of that country. Most vines were greater than 10years old, but younger vines (3 and 5 years old) were also found to be infected. External symptoms, includingdieback, tiger striped leaves, berry symptoms (shrivelling, insufficient colouring) and apoplexy, resembledthose found on grapevines in Europe and the USA, although the typical tiger stripe symptom was observedless frequently. The internal stem and trunk symptoms were similar to European symptoms, and includedwhite rot, black and brown wood streaking, brown necrosis within white rot, sectorial brown necrosis andbrown/red/margins next to decay, which often included back lines delimiting white decay. The fungi isolatedmostly from the white rot were basidiomycetes species (30.4%). Black and brown wood streaking was primarily caused by Phaeomoniella chlamydospora (45.4%). Brown necrosis within the white rot was linked to colonization by basidiomycetes (20.4%), Phaeoacremonium aleophilum (15.9%) and Pa. chlamydospora (13.6%). Phaeomoniella chlamydospora (20.8%) and Botryosphaeriaceae species (10.7%) were isolated the most fromthe sectorial brown necrosis and Pa. chlamydospora (29.1%) from the brown/red margins and black lines next to decay. Given the wide distribution of esca complex wood and foliar symptoms in the grape growing regions investigated, this disease should be considered as an important limiting factor in the productive lifespan of vineyards and the quality of produce from grapevine in South Africa.