Stephen Jordan, University of Wisconsin-Madison
Effects of ringspot virus. From L to R, graft union necrosis, aerial rooting, and in the vineyard. Photos by Bob Martin, USDA-ARS.
Grapevines affected by Ringspot Virus Decline show shortened internodes with small, distorted leaves that are approximately one third the size of a healthy leaf. Other leaf symptoms include yellow line patterns and flecks along veins, and in some cases, distortion can occur producing an oak-leaf pattern. Berry cluster set is reduced, and clusters often have uneven ripening. In the first year of infection, detection is often difficult. In the second year, shoot growth is limited, because buds arising from infected tissue are more susceptible to winterkill. By the third year, growth is limited to suckers located near the base of the trunk and all new growth is stunted. The vine eventually dies. This disease occurs sporadically in Vitis vinifera grapes (e.g., 'Chardonnay', 'Cabernet Sauvignon', 'Riesling') and interspecific hybrids (e.g., 'Vidal Blanc', 'Marechel Foch'). Vitis labrusca grapes (e.g., 'Niagara', 'Delaware') are resistant. The symptoms can differ significantly in different geographical regions, typically with greater severity in colder regions due to reduced cold hardiness of buds. The disease also has several other common names, such as "little grape" and "grape yellow vein".
Currently, there are no chemical control options for ringspot virus decline. The use of a nematicide can delay onset of the disease in re-plant and at-risk vineyards.
Ringspot virus decline is caused by either of two nepoviruses: tomato ringspot virus (TomRSV), or tobacco ringspot virus (TMRV), both of which are transmitted by dagger nematodes (Xiphinema spp.), and via seeds and cuttings. The nematodes acquire the virus from feeding on infected roots of grape or weed species. The nematode vectors retain the virus for long periods of time. Both TomRSV and TRSV can infect many common weeds in vineyards, including dandelions, sheep sorrel, common chickweed, and red clover. Because of this, it is not uncommon for these viruses to be present on land used to establish new vineyards. While TomRSV and TMRV can produce disease symptoms in grapevine that are identical, there are some important differences between the two. TomRSV infects a wide range of fruit crops and is considered one of the most economically important viruses infecting fruit crops in the northeastern United States, whereas TMRV does not infect other deciduous fruit crops. TMRV is also a more common problem in Vitis vinifera grapes.
Grapevine Decline in Pennsylvania & New York, Pennsylvania State University
Reviewed by Damon Smith, Oklahoma State University and Michelle Moyer, Washington State University