Identification of nonhost cover crops of the three-cornered alfalfa hopper (Spissistilus festinus)

Authors: Kron, Cindy; Sisterson, Mark

Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2020
Publication Date: 6/9/2020
Citation: Kron, C.R., Sisterson, M.S. 2020. Identification of nonhost cover crops of the three-cornered alfalfa hopper (Spissistilus festinus). American Journal of Enology and Viticulture. 71(3):175-180. https://doi.org/10.5344/ajev.2020.19069.
DOI: https://doi.org/10.5344/ajev.2020.19069

Interpretive Summary: Grapevine red blotch virus (GRBV) is an economically important pathogen of wine grape cultivars that is transmitted by the three-cornered alfalfa hopper. Cover crops are commonly planted in vineyards and some serve as feeding and reproductive hosts for the three-cornered alfalfa hopper, although limited information is available about which cover crops support three-cornered alfalfa hopper populations. In this study, the suitability of fifteen commonly planted cover crops for three-cornered alfalfa hopper feeding and reproduction was determined. Five of the fifteen tested cover crops tested (orchard grass, creeping red fescue, fawn tall fescue, hard fescue, and California poppy) did not support three-cornered alfalfa hopper feeding or reproduction. Results of this study will aid winegrape growers and vineyard managers in selecting cover crop species that do not support three-cornered alfalfa hopper populations, thereby limiting the spread of GRBV.

Technical Abstract: 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. Spissistilus festinus feeds and reproduces on a variety of plant species found in and around vineyards including certain cover crops and weeds. The ability of S. festinus to feed and reproduce on 15 commonly planted cover crops was determined. In no-choice tests, purple vetch, berseem clover, annual ryegrass, buckwheat, Trios triticale, and Zorro fescue supported S. festinus survival and reproduction. In contrast, orchard grass, creeping red fescue, fawn tall fescue, hard fescue, and California poppy did not support S. festinus survival or reproduction. Relative preference for hosts that supported reproduction was determined in choice tests. The legume species (purple vetch and berseem clover) exhibited higher nymph emergence than the non-legume cover crops (Zorro fescue, Trios triticale, buckwheat, and annual rye grass). Minimizing the abundance of host plants in vineyards is likely to suppress S. festinus populations and, in turn, reduce vector-mediated spread of GRBV in vineyards.