WINETECH Technical Yearbook 2020

Eutypa-like fungi associated with grapevine cankers and dieback

grapevine have been attributed to the fungal pathogen Eutypa lata. Recent studies, how- ever, have reported the occurrence of several Eutypa-like species (family Diatrypaceae) on grapevines affected with cankers, worldwide. These findings led to several investigations where many of the newly discovered species were found to occur more abundantly and widely distributed than E. lata. Similar to other grape-growing countries, canker pathogens are important in South Africa, but little information is currently available about the occurrence and identity of Eutypa-like species in South African vineyards.

The aim of this study was to determine the occurrence of Eutypa-like species associated with dieback and canker- affected grapevines and to determine their status as grapevine pathogens. INTRODUCTION The trunk disease complex which compris- es of grapevine canker diseases, including Eutypa dieback, Phomopsis dieback, as well as Botryosphaeria dieback and can- ker, is responsible for shortened life span of vineyards and severe losses as a result of vineyard re-establishment and reduced yields. For many decades, canker diseases on

OCTOBER 2020

PROVIDENCE MOYO 1 , LIZEL MOSTERT 1 & FRANCOIS HALLEEN 2 : 1 Department of Plant Pathology, Stellenbosch University, Stellenbosch; 2 ARC Infruitec-Nietvoorbij, Stellenbosch KEYWORDS: Diatrypaceae, tandpyn, grapevine trunk diseases

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PHOTO 1. Symptom types targeted during grapevine surveys. (A) Dying spur (arrow) observed in a Cabernet Sauvignon vineyard. (B) Dying spur cut through the pruning wound revealing internal symptoms. (C) Wedge-shaped necrosis in grapevine cordon. (D) Stromata, showing fruit body cavities of Cryptovalsa ampelina, on dead grapevine wood. Fungal spores which are able to infect healthy vines are produced within these structures.

WINETECH TECHNICAL YEARBOOK 2020 74