Assessing the relationship between cordon strangulation, dieback, and fungal trunk disease symptom expression in grapevine

Abstract

Grapevine cordons wrapped tightly around the cordon wire during establishment may be susceptible to an early occurrence of decay and dieback symptoms. A loss of productivity is often observed in older permanent cordons that have been constricted in this fashion but is not unique to them. Other factors of decline, such as fungal trunk disease infection, also play a significant role in perennial wood decline. This study aimed to quantify the impact of different contributors to cordon decline, including cordon strangulation and incidence of Eutypa lata infection and to investigate their relationship to each other. A survey was conducted over two seasons at ten vineyard sites to visually assess and capture images for algorithmic analysis of vines displaying varying degrees of cordon strangulation, cordon dieback, and characteristic foliar symptoms of Eutypa dieback. Rather than finding evidence of cordon strangulation being a driving force behind cordon decline, there was actually a trend of lower severity of dieback observed, with cordons displaying the greatest degree of strangulation. There was also a trend for increased foliar symptoms in relation to an increase in the degree of strangulation, but it is difficult to assign causality in this regard, as the occurrence of foliar symptoms may be influenced by a multitude of factors, including climatic conditions. Further research quantifying the extent to which xylem morphology and functionality are compromised by constrictive pressure in severely strangled cordons could provide further insight into this condition and the effect it could have on vine health and defence response.

Keywords

• cordon
• <i>Eutypa</i>
• disease resistance
• trunk disease
• water status