Spatial Roguing Reduces the Incidence of Leafroll Disease and Curtails its Spread in a Finger Lakes ‘Cabernet Franc’ Vineyard

Abstract

Leafroll is one of the most economically important viral diseases of grapevines worldwide. Grapevine leafroll-associated virus 1 (GLRaV-1) and grapevine leafroll-associated virus 3 (GLRaV-3) are prevalent in New York vineyards in which low-density grape mealybug populations reside. A five-year experiment was performed in a commercial ‘Cabernet franc’ vineyard in the Finger Lakes region of New York to test the influence of spatial roguing, i.e., the elimination of virus-infected vines and their two immediate within-row neighbors on each side, on the annual incidence of GLRaV-1 and GLRaV-3. In a second treatment, spatial roguing was combined with insecticides. Vines eliminated in both spatial roguing treatments were replaced by clean vines derived from virus-tested stocks. The objective of this study was to reduce temporal virus incidence to less than 1% over two consecutive years and limit virus spread. In both spatial roguing treatments, virus incidence was reduced from 5% in 2016 to less than 1% in 2020-2021. Among vines in the insecticide-free, non-rogued control treatment, virus incidence increased from 5% to 16% from 2016 to 2021. Insecticides applied in 2016-2021 helped significantly reduce grape mealybug populations to near zero annually, while populations in the untreated control vines were 57 to 257-fold higher during the same period. However, insecticides contributed relatively little to limit the number of newly infected vines. Together, these findings highlight the salient contribution of roguing to an overall leafroll disease management response in a vineyard with low disease incidence and low grape mealybug abundance. To our knowledge, this is the first report on the effectiveness of spatial roguing at reducing the annual incidence of leafroll disease in a vineyard.