Spinach Downy Mildew Fungicides Evaluated (April 13, 2016)

Data from our recently completed spinach downy mildew fungicide evaluation trial have been collected and analyzed. Highlights from the study are presented here. The susceptible variety Viroflay was used in this trial, which consisted of 25 treatments containing fungicides either applied solo for the duration of the trial (to assess relative performance of individual fungicides) or applied within a mixture or alternation program. The average percentage of infected leaves within the four replicate nontreated plots was 69%. On the other hand, one treatment program, consisting of Orondis+Ridomil Gold applied at emergence (Feb 24) followed later by Actigard (Mar 4) and then Revus (Mar 11), reduced incidence of downy mildew to 1.5%. Other treatments, including Orondis+Ridomil Gold applied once at seedling emergence (Feb 24) as well as individual applications of Actigard or Revus made twice (Mar 4 and 11), reduced final incidence of downy mildew to 2.0, 12.5, and 33.5%, respectively. Two biofungicides evaluated individually reduced disease incidence from 69% in nontreated plots to the 50 to 55% range. Clearly, the search needs to continue for effective fungicides for the organic spinach production community.

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To contact Mike Matheron go to: matheron@ag.arizona.edu.