Survey of green sharpshooter populations in and near vineyards in the San Joaquin Valley

Authors: Sisterson, Mark; DAANE, KENT - University Of California

Submitted to: CDFA Pierce's Disease Control Program Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 10/11/2010
Publication Date: 11/1/2010
Citation: Sisterson, M.S., Daane, K. 2010. Survey of green sharpshooter populations in and near vineyards in the San Joaquin Valley. CDFA Pierce's Disease Control Program Research Symposium, San Diego, CA, Dec 15-17, 2010. Available: http://www.cdfa.ca.gov/pdcp/2010_Research_Proceedings.html.

Interpretive Summary:

Technical Abstract: Pierce’s disease and almond leaf scorch disease have an episodic history in California that predates arrival of the glassy-winged sharpshooter. Within California’s Central Valley, the green sharpshooter (Draeculacephala minerva) is the most abundant and widely distributed vector of X. fastidiosa. Previous reports indicate that grape and almond are occasional hosts of D. minerva, whereas grassy weeds present in pastures and irrigated alfalfa fields are preferred hosts. To better understand movement of D. minerva into vineyards, eight vineyards in the San Joaquin Valley were sampled. At each vineyard, potential source habitats for D. minerva were identified: pastures, alfalfa fields, and grassy ditches. Abundance of D. minerva in source habitats was assessed using sticky traps and/or sweeps. To document movement of D. minerva into vineyards, 16-20 sticky traps were placed around each vineyard and changed biweekly. Finally, weed ground cover in each vineyard was evaluated and if present swept on a monthly basis. Abundance of D. minerva was greatest in permanent pastures followed by alfalfa fields. Populations of D. minerva were largely absent from grassy ditches. Catches of D. minvera on traps surrounding vineyards was rare, but occurred at 7 of 8 vineyards during the study. As a blunder trap was used and traps covered only a small fraction of vineyard perimeter, low trap catches were unsurprising and the fact that catches occurred at nearly all sites suggest regular movement of D. minerva into vineyards. However, D. minerva was observed in weedy ground cover at only two vineyard sites and was never observed on the vines themselves, suggesting that movement into vineyards was transient. Lack of establishment of D. minerva populations in vineyards may be due to the ephemeral nature of vineyard weed populations. The results reinforce previous reports that grape is not a preferred host of D. minerva and that habitats outside of vineyards are likely to play a key role in D. minerva population dynamics, particularly locations with permanent irrigated grasses.