Influence of Pruning Measures on Recovery of Bois Noir‐infected Grapevines

In recent years, visual and analytical observations revealed a significant increase of ‘Bois noir’ (BN) in Austrian vineyards. Removing infected parts by pruning can prevent or reduce spread of the pathogen within the vines. Knowledge about the effect of pruning practices on recovery rates is essential for grapevine growers. Vines showing BN for the first time were visually categorized into classes of symptoms according to disease severity. In the ensuing winter, plants were pollarded 15 cm above the graft union (511 vines), cane pruned (529 vines) or spur pruned (heavy pruning of canes leaving spurs only; 31 vines). Pollarding resulted in significantly higher recovery rates (yearly average 62–84%) in the next growing season and significantly lower recurrence rates in the following years than cane pruning (yearly average 29–49% in the next growing season). Spur pruning was statistically indistinguishable from cane pruning. Our data allowed the conclusion that extensive removal of infected wood is crucial for immediate and persistent success of pruning measures. Recovery was significantly influenced by the severity of BN, by the cultivar and by the observation year. With pollarding treatments, a significant correlation between recovery and plant age was noticed.