Cucurbit downy mildew (CDM), caused by Pseudoperonospora cubensis, is a devastating foliar blight of cucumbers that re-emerged in Michigan in 2005 when host resistance failed. CDM is resistant to several fungicides and Michigan growers rely on fungicide recommendations based on local data. Our goal was to improve Michigan pickling cucumber growers CDM management by: 1) Evaluating fungicides over three field seasons for their ability to protect a susceptible cultivar and 2) Compare intermediately resistant (IR) cultivars ‘Peacemaker’ and ‘Citadel’ with susceptible cultivars when treated with three fungicide programs or not treated. CDM severity was visually assessed and the area under disease progress curve calculated. Trials were harvested within the spray interval. Mandipropamid, propamocarb, fluxapyroxad+pyraclostrobin, copper octanoate, and dimethomorph were similar to the control for CDM severity in 2015; cymaxonil was similar to the control in 2016 and in 2017, famoxadone+cymoxanil and fluopicolide were additionally similar to the control. Several fungicides yielded higher than the control, oxathiapiprolin mixed with either chlorothalonil or mandipropamid, mancozeb, dimethomorph+amectoctradin, zoxamide+mancozeb, ethaboxam, cyazofamid, chlorothalonil, and fluazinam. IR cultivar control plots were less diseased and higher yielding than the susceptible cultivar control plots in 2016; ‘Citadel’ was similar to susceptible cultivar control plots in 2017. In 2016, Program 3 provided disease protection for the susceptible standards that was better than Program 1. Program 3 and 2 provided similar levels of disease control for ‘Peacemaker’, ‘Citadel’ and ‘Vlaspik’ in 2016; all cultivars in 2017.
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