Potential impacts of the ring nematode, Mesocriconema xenoplax, on grapevines in British Columbia: A microplot study

The wine grape industry in the Okanagan Valley of BC has grown substantially in the past three decades in terms of acreage and economic benefits. Plant-parasitic nematodes are soil-dwelling microscopic roundworms that are pests of many types of crops including grapevines. The ring nematode, Mesocriconema xenoplax, which is a significant pest in older grape-growing regions, was recently been found to be widespread in Okanagan vineyards. In order to measure the effects of a local population of this nematode on the types of vines grown in the Okanagan, the researchers inoculated root zone soil of self-rooted ‘Merlot’ vines and ‘Merlot’ vines that had been grafted onto 3309C, 44-53 and Riparia Gloire rootstocks. They then compared growth of the inoculated vines to those that were not inoculated over four years under field conditions. The researchers found that the ring nematodes multiplied to comparable levels on all rootstocks, indicating that none of them were resistant to the ring nematodes. The nematodes suppressed growth of the self-rooted ‘Merlot’ vines by 58%, and trunk diameter by 40% over the four years. Trunk growth of 3309C rootstock also was reduced by 45%, but growth of the other rootstocks were not as severely affected. The results suggest that ring nematodes are likely affecting vineyard health and productivity in the region, but that rootstocks may vary in their tolerance to the nematodes and selection of rootstocks should be considered in future vineyard replant management programs.