Partial Uprooting and Pulling to Induce Recovery in Bois noir‐Infected Grapevines

Grapevine yellows (GY) are diseases caused by phytoplasmas, which are able to induce severe loss of production and death of plants. Bois noir (BN) and Flavescence dorée are the most important GY diseases prevalent in several European countries. As of now, there are no known effective disease‐control methods for application in grapevines infected by these phytoplasmas. In these plants, it is possible to have, remission of these symptoms, better known as ‘recovery’. In April 2006 in the Marche region, central‐eastern Italy, grapevines cv. Chardonnay, Verdicchio and Sangiovese grafted onto Kober 5BB; rootstock symptomatically infected by VK type II BN were subjected to partial uprooting, which was effected by breaking most of their roots using a small excavator. Almost all of these plants failed to show disease symptoms in the autumn of 2006 and 2007. Similar trials were carried out on BN‐infected plants cv. Chardonnay grafted onto 420A rootstock in 2006 and 2007; in this case, the treatment was only partially successful in both these years. In another trial in April 2007, BN‐infected plants cv. Chardonnay grafted onto 420A rootstock and cv. Primitivo grafted onto Kober 5BB, rootstock were ‘pulled’ and some of these showed no disease symptoms in the following autumn, whereas others had only mild infections. Partial uprooting and pulling are agronomical practices that induce stress in the plants. In the case of grapevines affected by GY, such stress can result in the recovery of the vines. However, the effectiveness in the induction of recovery in these treatments can depend on the rootstock.