Identification of Nonhost Cover Crops of the Three-Cornered Alfalfa Hopper (Spissistilus festinus)

The three-cornered alfalfa hopper, Spissistilus festinus (Say) (Hemiptera: Membracidae) was identified as a vector of grapevine red blotch virus (GRBV) in a greenhouse study. GRBV impacts berry maturation, resulting in reduced accumulation of total soluble solids, increased titratable acidity, and altered levels of secondary metabolites that affect color, flavor, and aroma of finished wine made from infected grapes. S. festinus feeds and reproduces on a variety of plant species found in and around vineyards, including certain cover crops and weeds. The suitability of 15 commonly planted cover crops for S. festinus adult feeding and oviposition was determined. In no-choice tests, purple vetch, berseem clover, annual ryegrass, buckwheat, Trios triticale, and Zorro fescue supported survival of adult S. festinus, oviposition, and emergence of nymphs. In contrast, orchard grass, creeping red fescue, fawn tall fescue, hard fescue, and California poppy did not support survival of adult S. festinus, nor were nymphs observed. Relative preference for hosts that supported nymph emergence was determined in choice tests. The legume species (purple vetch and berseem clover) exhibited higher nymph emergence than the nonlegume cover crops (Zorro fescue, Trios triticale, buckwheat, and annual ryegrass). Cultivating cover crops that do not support S. festinus survival or oviposition may aid in reducing the risk of S. festinus moving into and establishing in vineyards.