Symptoms and fungi associated with esca in South African vineyards
In the past, only a few incidences of esca diseased grapevines were reported from the Slanghoek and Rawsonville areas of South Africa. The damage was believed to be of little importance and therefore the disease has 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 in the Western Cape, Northern Cape and Limpopo provinces of that country. Most vines were greater than 10 years old, but younger vines (3 and 5 years old) were also found to be infected. External symptoms, including dieback, tiger striped leaves, berry symptoms (shrivelling, insufficient colouring) and apoplexy, resembled those found on grapevines in Europe and the USA, although the typical tiger stripe symptom was observed less frequently. The internal stem and trunk symptoms were similar to European symptoms, and included white rot, black and brown wood streaking, brown necrosis within white rot, sectorial brown necrosis and brown/red/margins next to decay, which often included black lines delimiting white decay. The fungi isolated mostly 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 from the 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.