Leaf and fruit symptoms can be used to diagnose leafroll disease in many varieties of V. vinifera grapevines. Symptoms are not reliable as an indicator of leafroll disease in most North American species and hybrids, including most rootstock varieties. The lack of symptoms in any type of grapevine does not guarantee freedom from infection by the viruses which are the causal agents of leafroll disease.
Visual symptoms develop in both leaves and fruit of most vinifera varieties as the crop matures. The most distinct leaf symptoms appear between the time of harvest and leaf fall. On affected vines, the margins of the leaf blades roll downward, starting with the basal leaf on the cane. Areas between the major veins turn yellow or red, depending on whether the variety produces white- or red-colored fruit. In some varieties, the area adjacent to the major veins remains green until late fall.
The most important effect of leafroll disease is a reduction in the yield and quality of fruit from infected vines. Yield losses of 10 to 20% are fairly typical. Because leafroll damages the phloem of infected vines, sugar accumulation is delayed and anthocyanin production is reduced. Fruit from infected vines will be low in sugar, poorly colored and late ripening. In some varieties, fruit maturity is delayed so that fruit on the affected vine may be pale or even whitish at harvest when fruit on healthy vines is ripe.
There are currently nine recognized, serologically distinct viruses associated with grapevine leafroll disease. These are unique, closely related viruses, not strains of the same virus. Taxonomically, the nine GLRaVs are classified in the virus family closteroviridae, which is characterized by large, flexuous rod-shaped particles with size range of 1250-2200 nm in length. The nine viruses are Grapevine leafroll associated virus 1 through 9 (abbreviated GLRaV-1, -2 and so on).
See also Virus Diseases.
Grapevine Leafroll Disease - An Increasing Problem for California Vineyards was a UC Davis Extension Seminar held June 10, 2008 at UC Davis. This link contains videotaped presentations that can be individually selected.
Grapevine Leafroll Disease Symposium 2.0 was held June 2, 2009 as a followup to the earlier seminar. Updated research results and new speakers were included. This link contains videotaped presentations that can be individually selected.
Alkowni, R., Rowhani, A., Daubert, S., and Golino, D.A. 2004. Partial Characterization of a new Amepelovirus associated with grapevine leafroll disease. Journal of Plant Pathology 86: 123-133.
Flaherty, D., Christensen, L., Lanini, W., Marois, J., Phillips, P., and Wilson, L. 1992. Grape Pest management 2nd Edition. Agricultural Sciences Publications, #3343, University of California, Oakland, CA.
Golino, D.A. and Almeida, R. 2008. Studies needed of vectors spreading leafroll disease in California vineyards.(pdf) Sidebar. California Agriculture 62(4):174.
Golino, D., Rowhani, A., and Sim, S. 2010. Leafroll Color Atlas (PowerPoint PDF). Foundation Plant Services, University of California, Davis.
Golino, D.A., Sim, S.T., Osman, F., Aldamrat, R., and Rowhani, A. 2009. Grapevine viruses detected in wild grapes (Vitis californica). Phytopathology 99: S44. http://apsjournals.apsnet.org/doi/pdf/10.1094/PHYTO.2009.99.6.S1
Golino, D.A., Sim, S.T., Osman, F., Aldamrat, R., Klaassen, V., Rowhani, A. 2009. Survey of wild grapes, weed and cover crop species for grapevine viruses. Progrès Agricole et Viticole, p. 110-111. http://www.icvg.ch/archive.htm
Golino, D.A., Sim, S., Gill, R., and Rowhani, A. 2002. Grapevine leafroll disease can be spread by California mealybugs (PDF). California Agriculture 56 (6):196-201.
Golino, D.A., Weber, E., Sim, S., and Rowhani, A. 2008. Leafroll disease is spreading rapidly in a Napa Valley vineyard.(pdf) California Agriculture 62(4):156-160.
Klaassen, V.A. 2009. Discussions from Grapevine Leafroll Symposium 2.0. Foundation Plant Services Grape Program Newsletter. p. 13-16.
Klaassen, V. 2010. Leafroll Disease Research at FPS (pdf). FPS Grape Program Newsletter, Foundation Plant Services, University of California, Davis. October 2010, p. 16.
Klaassen, V. A., Sim, S. T., Dangl, G. S., Osman, F. A., Al Rwahnih, M., Rowhani, A., and Golino, D. A. 2011. Vitis californica and Vitis californica x Vitis vinifera hybrids are hosts for Grapevine leafroll-associated virus-2 and -3, and Grapevine virus A and B. Plant Disease 95 (in Press).
Martinson, T., Fuchs, M., Loeb, G. and Hoch, H. 2008. Grapevine Leafroll – an Increasing Problem in the Finger Lakes, the US and the World (PDF). Finger Lakes Vineyard Notes, 6: 6-11, Cornell University Cooperative Extension.
Rowhani, A., Uyemoto, J.K., Golino, D., and Martelli, G.P. 2005. Pathogen testing and certification of Vitis and Prunus species. Annual Review of Phytopathology 43: 261-278.
Pearson, R., and Goheen, A. 1988. Compendium of Grape Diseases. APS Press, St. Paul, Minnesota.
Tsai, C., Rowhani, A., Golino, D., Daane, K., and Almeida, R. 2010. Mealybug Transmission of Grapevine Leafroll Viruses: An Analysis of Virus–Vector Specificity (pdf). Phytopathology 100(8): 830-834.
Weber, E., Golino, D.A., and Rowhani, A. 1993. Leafroll disease of grapevines. Practical Winery and Vineyard. XIV: 21-24.
Weber, E., Golino, D.A., and Rowhani, A., 2002. Laboratory testing for grapevine virus diseases (PDF). Practical Winery and Vineyard XXII (2): 13-26.