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Poster: Biology & Disease Mgmt: Chemical Control


Season long management of potato silver scurf caused by Helminthosporium solani in Wisconsin
S. MACCHIAVELLI-GIRÓN (1), S. Jordan (1), J. Crane (2), A. Gevens (1) (1) University of Wisconsin-Madison, U.S.A.; (2) University of Wisconsin-Madison, U.S.A.

Silver scurf, caused by the fungus Helminthosporium solani, is a tuber blemish disease of increasing concern in potato production. The disease affects periderm quality and appearance, impacting marketability as well as storability. Cultural management strategies are limited and often impractical for large-scale growers, making fungicide applications an important component of integrated silver scurf management. Helminthosporium solani initially infects tubers in the field, and has secondary infection cycles during storage. Because inoculum can be reduced at multiple times during potato production, we conducted a full life cycle study in 2015 to evaluate the aggregated impact of fungicide selection and timing on silver scurf severity in ‘Dark Red Norland’ potatoes. Fungicides were applied at three times: at planting as seed or in-furrow treatments; in-field as a series of 3 foliar sprays; and post-harvest immediately before storage. Non-treated comparisons were included. The at-planting applications had the greatest impact on symptom severity, although the post-harvest treatments also contributed to disease reductions. The lowest severity resulted from the Maxim MZ (fludioxonil + mancozeb) seed treatment with the Stadium (fludioxonil + azoxystrobin + difenoconazole) post-harvest treatment. Along with cultural methods, at-plant and post-harvest fungicide treatments together were necessary for silver scurf control.