EVALUATION OF FUNGICIDES APPLIED VIA DRIP IRRIGATION FOR CONTROL OF SILVER SCURF ON POTATO IN WESTERN WASHINGTON.
Applied Research
Don McMoran
Agriculture and Natural Resources Extension Faculty- Director
Washington State University
Burlington
Abstract
The Silver Scruf pathogen infects the tuber periderm causing lesions that reduce marketability. Fungicides applied through drip irrigation were evaluated for effectiveness in controlling silver scurf and as an alternative to preplant fungicide treatments. The study established near Mount Vernon, WA at Washington State University NWREC on 21 May 2012. There were five treatments included: penthiopyrad applied at 45 days after planting (dap), penthiopyrad applied at 60 dap, azoxystrobin applied at 45 dap, and azoxystrobin applied at 60 dap, and a non-treated non-irrigated control. Azoxystrobin and penthiopyrad-treated plots were drip-irrigated. The trial was maintained with fertilizer and pesticide management practices standard for commercial potato production in the area. Plants were topped (mowed) and then sprayed with Diquat on 31 Aug 2012. Harvest took place on 10 Oct 2012 to ensure the maximum exposure to silver scurf inoculum in the soil. Each tuber was weighed and graded. Twenty-five potatoes from each plot were evaluated postharvest after 2 weeks of storage. Incidence of silver scurf was higher for the control plots (96.92%) as compared to azoxystrobin-treated at 45 dap and 60 dap (83.00% and 81.45%, respectively) and penthiopyrad-treated plots at 45 and 60 dap (76% and 74%, respectively). Control plots also had higher silver scurf severity (11%), as compared to plots treated with azoxystrobin at 45 and 60 dap (8% and 7.5%, respectively) and plots treated with penthiopyrad at 45 and 60 dap (7% and 6%, respectively).
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Authors: D. Mcmoran
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Mcmoran, D. Agriculture and Natural Resources Extension Educator- Director, Washington State University, Washington, 98233