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Potomac Division - Evaluation of fungicides for efficacy against pod rot of lima bean caused by Phytophthora capsici
A. A. KNESS (1), G. C. Johnson (2), N. M. Donofrio (1), T. A. Evans (1), E. G. Ernest (2), K. L. Everts (3), N. F. Gregory (1), H. N. Baker (2). (1) University of Delaware, Newark, DE, U.S.A.; (2) University of Delaware, Georgetown, DE, U.S.A.; (3) University of Maryland, Salisbury, MD, U.S.A.

Pod rot caused by <i>Phytophthora capsici</i> is a devastating disease of lima bean (<i>Phaseolus lunatus</i>) on the Delmarva Peninsula. Management of pod rot is often limited to fungicides.  However, only two fungicides, mefenoxam (Ridomil Gold), registered since 1992, and more recently, cyazofamid (Ranman) are registered for the management of pod rot.  Because growers have relied on mefenoxam for management, resistant populations of <i>P. capsici</i> have developed.  Ten fungicides, in addition to Ridomil and Ranman, were tested for their efficacy in controlling pod rot of lima bean. Two separate field trials were conducted at the University of Delaware’s Carvel Research and Education Center in Georgetown, Delaware in 2014. The first and second field locations had moderate and heavy disease pressure, respectively. Results indicate that all tested fungicides significantly reduced disease incidence when compared to the water control treatment in both trials. Applications of Ridomil, Ranman, Omega, and Zorvec consistently achieved in the greatest reduction of pod rot. There was no significant difference in yield among treatments in the first field location (moderate disease pressure). However, the control plots in the second field location (heavy disease pressure) yielded significantly less, with potential yield loss over 86%. These trials indicate that there are additional fungicides with efficacy against <i>P. capsici</i> on lima bean which merits further research to support their labelling.

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