Prevalence, distribution, and role of Cryptovalsa ampelina in grapevine dieback in Australia
Summary
Objective
The project aims to address the following objectives:
- What is the prevalence and distribution of C. ampelina in Australia vineyards?
- Does C. ampelina contribute to the dieback symptoms observed in vineyards?
- Do E. lata and C. ampelina interact in antagonistically or synergistically in the vine?
- What are the environmental factors that favour the growth of C. ampelina?
- Are the current fungicides and biocontrol agents registered for Eutypa dieback also effective in managing C. ampelina in grapevines?
Background
Grapevine trunk diseases (GTDs) are considered a serious problem in all viticulture regions worldwide, causing dieback and, eventually, the death of grapevines. This leads to yield reduction, reduced vine longevity, and significant economic losses worldwide.
GTD pathogens are mainly spread in mature vineyards by infecting and colonising pruning wounds (van Niekerk et al. 2011, Úrbez-Torres and Gubler, 2011). The highest risk of infection for vines is during pruning, due to the high number of wounds occurring at the same time (Rolshausen et al. 2010). These wounds are vulnerable to infection for 2-3 weeks after pruning (SAR1205, SAR1701-1.1, Sosnowski et al. 2023). In addition, each vine can be infected with one or more GTD fungi (Gramaje et al. 2017).
In Australia, Eutypa dieback (ED) is one of the most important GTDs affecting Australian vineyards. ED is predominantly caused by Eutypa lata, however the pathogen Cryptovalsa ampelina has also been detected regularly in grapevines and spore traps in Australian vineyards (Pitt et al. 2010 and Trouillas et al. 2011, Billones-Baaijens et al. 2023, SAR1701-1.1). C. ampelina has been studied in several countries, such as South Africa (Mostert et al. 2004) and Spain (Luque et al. 2006) concluding that Cryptovalsa was pathogenic, but not a highly virulent pathogen of grapevines. Despite this fact, the role Cryptovalsa plays in overall GTD development and progression in grapevines is still unknown.
The elucidation of fungal temporal dispersal patterns may assist in viticultural practices to avoid infections during the pruning season. The use of spore traps is one of the main methodologies to study the epidemiology of these diseases in field conditions (Billones-Baaijens et al. 2018; Billones-Baaijens et al. 2023, González-Domínguez et al., 2020). The application of wound protectants is critical in preventing new GTD infections. A preventive spray application on wounds within 6 days of pruning can provide up to 3 weeks of protection (Sosnowski, 2019, SAR1205, SAR1701-1.1). Currently, fungicides and biological control agents registered in Australia for Eutypa dieback are based solely on efficacy data against E. lata. The efficacy of these fungicides and biological control agents for C. ampelina is currently unknown.
This research project aligns with Wine Australia’s Strategic Plan 2020-2025 “New and improved practices for the sustainable management of endemic pests and diseases are available to the sector” and is embedded in the Wine Australia GTD project SAR1701.3 “Management and diagnosis of grapevine trunk disease in vineyards and nurseries”. Understanding the role of prevalent fungi in Australian vineyards is important in developing robust control strategies that increase vineyard longevity and minimise vineyards from declining due to GTDs.