Effect of training-pruning regimes on Eutypa dieback and performance of ‘Cabernet Sauvignon’ grapevines

Abstract

SummaryThe effects of training-pruning regimes on Eutypa dieback, vigour, yield and fruit composition were evaluated in ‘Cabernet Sauvignon’ grapevines from 1991 to 2004 in Galt, California, USA. Mechanical pruning at bud swell, and minimal pruning (trimming only in Summer) gave the least dieback. In contrast, pruning of dormant vines trained on either a bilateral cordon or a Sylvoz system increased wounding and dieback. Hand pruning of head-trained vines gave fewer cuts and less dieback, compared with vines trained as bilateral cordons or Sylvoz. Dieback reduced the extension of fruiting arms on bilateral cordon- and Sylvoz-trained vines with dormant season pruning, whereas arms were healthy after mechanical and minimal pruning. Hand-pruned vines (bilateral cordon, Sylvoz or head) had greater pruning weights, fewer shoots and clusters, heavier clusters, and lower yields than vines pruned mechanically or minimally. Despite the presence of dieback, yields did not decline over 14 years (except for Sylvoz-trained vines from 2002, and bilateral cordon-trained vines from 2003). Fruit had lower °Brix and pH, and higher titratable acidity in some years, suggesting possible delays in fruit ripening on minimally-pruned vines. Mechanical pruning at bud swell and Summer trimming can minimise Eutypa dieback while maintaining yield and fruit quality. Training-pruning regimes that require early pruning and that generate large numbers of wounds when vines are dormant should be avoided where Eutypa is a concern.