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Poster: Biology & Disease Mgmt: Chemical Control


Laboratory and field evaluation of fungicides for management of Phytophthora blight of pumpkin, caused by Phytophthora capsici
M. BABADOOST (1), J. de Souza (2), T. Reboucas (2), Y. Xiang (1) (1) Department of Crop Sciences, University of Illinois, U.S.A.; (2) Deptment of Plant Science, Southwest Bahia University State, Brazil

Phytophthora blight, caused by Phytophthora capsici, is a destructive disease of cucurbits and peppers in Illinois and worldwide. Fungicide use is an important component of management strategies of Phytophthora blight of cucurbits. Studies were conducted in laboratory and field to evaluate efficacy of selected fungicides for management of Phytophthora blight of pumpkin in Illinois. In the laboratory, sensitivity of five P. capsici isolates from Illinois was evaluated to three registered fungicides (cyazofamid, dimethomorph, mandipropamid) for use on cucurbits and two experimental fungicides (A20941OD, A20942SC) for control of Phytophthora spp. Development of colony and production of sporangia and zoospores of the isolates were assessed at different concentrations from 0 to 10 µg/ml for registered fungicides and from 0 to 200 µg/ml for experimental fungicides on V8 juice agar medium in Petri plates. The isolates were highly sensitive to mandipropamid, intermediately sensitive to cyazofamid and A20941OD, and less sensitive to dimethomorph and A20942SC. In the field experiment in 2014, incidence of pumpkin fruit rot caused by P. capsici was 31% in control plots and 5, 10, 2, and 11% in the plots treated with cyazofamid, dimethomorph, mandipropamid, and A20942SC, respectively. In 2015, incidence of pumpkin fruit rot caused by P. capsici was 69% in control plots and 42, 21, and 18% in the plots sprayed with cyazofamid, dimethomorph, and mandipropamid, respectively.