Grapevine red blotch disease, caused by grapevine red blotch virus (GRBV; genus Grablovirus family Geminiviridae), is an emerging concern among grape growers. Parallel studies in New York and California isolated GRBV from grapevines, and it was subsequently documented to occur across multiple states in the United States and also in Canada and South Korea.
The virus is presumably spread through infected plant material; however, studies suggest transmission is also possible through insects (i.e., Spissistilus festinus). The economic implications of GRBV can be quite significant, with great losses due to lower yields, quality price penalization, and ultimately, replanting costs.
GRBV may induce some symptoms similar to those associated with the long-known grapevine leafroll-associated viruses (GLRaVs), inducing red pigmentation in leaf margins and veins in red-skinned grape varieties. This may not be the only similarity, as GRBV is suspected to impair grape ripening and reduce yields just as GLRaVs do. Although it is possible to distinguish the visual symptoms of the two diseases, it can take an experienced eye to do so, and is therefore likely that GRBV presence was masked for many years by the widespread occurrence of GLRaVs in commercial vineyards.