Principal Investigator: Michelle Moyer, Washington State University, Prosser
Contact: michelle.moyer@wsu.edu (509) 786-9234
Co-PIs: Bernadette Gagnier, WSU; Inga Zasada, USDA-Agricultural Research Service, Corvallis
Summary: The Washington State wine industry supported research to explore the impacts of site management practices on northern root-knot nematode (Meloidognye hapla). A previous survey found that more than 60 percent of own-rooted vineyards in Washington were infested with northern root-knot nematode. Damage is caused when the nematode feeds on grapevine roots, which then induces small galls on the roots that can restrict water and nutrient uptake, resulting in poor vine establishment in young vines or exacerbated decline in stressed vines. Pre-plant management strategies that were studied as part of this research for northern root-knot nematode were fumigation and resistant rootstocks. This study focused on the use of a fallow period between vineyard removal and re-establishment.
Growers of 38 fallowed vineyard sites participated in the study. Results suggest that at least one year of fallow may be necessary before observable northern root-knot nematode population densities begins to decline. Sites where the weeds in the fallowed land were strategically mowed did not reduce population densities more than the fallow alone treatment. A small percentage of the fallowed sites were irrigated, but the sample size was too small to be conclusive. A use of cover crops in the fallowed sites did not reduce the nematode densities. Also, tillage was not found to be a significant factor.
When sites were fallowed for longer than 1 year, they had lower densities than the 1 year fallow treatment, however, there is an economic cost for ground kept out of production. Because most vineyards sites in this study had some level of the nematode in the soil, it emphasizes the need for a multi-pronged approach for nematode management in vineyard replant scenarios of fallow, resistant or tolerant rootstock and planting of nematocidal cover crops.