A Grapevine red blotch virus vector: the three-cornered alfalfa hopper (3CAH), Spissistilus festinus, in Napa vineyards

Authors: PRETO, CINDY - University Of California; Sudarshana, Mysore; ZALOM, FRANK - University Of California

Submitted to: Trade Journal Publication
Publication Type: Trade Journal
Publication Acceptance Date: 2/1/2019
Publication Date: 2/1/2019
Citation: Preto, C.R., Sudarshana, M.R., Zalom, F.G. 2019. A Grapevine red blotch virus vector: the three-cornered alfalfa hopper (3CAH), Spissistilus festinus, in Napa vineyards. American Vineyard Magazine. 28:14-18.

Interpretive Summary:

Technical Abstract: In 2008, a Cabernet Sauvignon vineyard block located in Oakville Research Station, Napa County, displayed disease symptoms similar to grapevine leafroll, but the vines tested negative for all grapevine leafroll-associated viruses. Further research resulted in the discovery of a previously unknown virus, later named Grapevine red blotch virus (GRBV), which was determined to be the causal agent of Grapevine red blotch disease (GRBD). Infected red grape varieties show a red blotchy pattern in the leaves with red veins and flat leaf margins. Symptoms in white grape varieties are more subtle, resulting in yellowing between the veins of the leaf blade that turns brown later in the season. GRBD delays fruit maturity, lowers °Brix, and affects the production of secondary metabolites that contribute to aspects of wine quality such as color, flavor, and aroma. Grapevine red blotch positive vines were mapped in a research block located in Oakville Research Station from 2011 to 2014 by M. Sudarshana and his associates. A 5.2% average annual increase of GRBD was documented over four years indicating that spread was occurring and possibly by an insect vector. In 2016, Bahder et al. showed the three-cornered alfalfa hopper (3CAH), Spissistilus festinus, to be a vector of GRBV in a greenhouse study. Most of what is known about 3CAH biology comes from research conducted in the southern United States where it is an occasional economic pest of alfalfa, peanuts, and soybeans. Prior to being named a vector of GRBV, the 3CAH was considered to be a minor pest of grapevines due to its girdling behavior of petioles and young shoots. Until recently, very little research had been pursued on 3CAH in California, and no research conducted in vineyards was published. In an effort to minimize the spread of GRBV in the vineyard by applying measures to control 3CAH, more information about its biology and behavior in relation to vineyards was needed.