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Deficit irrigation and grapevine red blotch disease management

Achala KC: Southern Oregon Research and Extension Center, Oregon State University

<div>Grapevine Red Blotch Disease (GRBD) is a newly identified disease of grapevines caused by grapevine red blotch virus (GRBV). The economic loss associated with the disease is reduction in fruit quality and delayed ripening. The imposition of moderate water deficits is a common viticultural practice to advance ripening and improve fruit quality. However, the stress experienced by vines under deficit irrigation can potentially amplify the negative effects of GRBD. Research was conducted to understand interaction between GRBV and deficit irrigation on disease development and fruit quality. A split-plot field experiment with two irrigation treatments, a grower control (GC) and a deficit irrigation (DI); and two vine statuses, healthy and infected, were arranged in a randomized complete block design. Deficit irrigation was imposed by irrigating 66% of the grower standard practice and inline water meters were used to quantify applied water amounts. Vine health status was determined by PCR-based assays as infected or non-infected with GRBV. Disease severity was recorded every week after the first symptom appearance on infected vines. No significant interaction between water and vine health status to disease severity was observed. However, the stem water potential of infected vines was significantly higher compared to healthy vines in both dry and wet treatments. In addition, overall fruit quality of the infected vines was better in the GC irrigation treatment than the DI treatment. The results suggest that keeping vines well-watered may mitigate some of the negative effects of GRBV infection.</div>