Data from our recently completed 2017 spinach downy mildew fungicide evaluation trial have been collected and analyzed. The spinach variety Lanzarote was used for this trial, the highlights of which are presented here. This trial consisted of 27 treatments containing conventional and biologically based fungicides 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 five replicate nontreated plots was 60%. On the other hand, three treatment programs composed of Ridomil Gold + Quadris applied at emergence (Jan 25) followed by alternation with two additional treatments (Presidio + Forum, Prophyt, Orondis, or Actigard) on Feb 1, 13, and 21 reduced the incidence of downy mildew to a range of 1.8 to 2.2%. Also, downy mildew incidence ranged from 2.2 to 20% in plots treated with Ranman on Feb 1, 13, and 21. However, disease levels in plots treated with individual biofungicides ranged from 40 to 60%. Clearly, the search for effective fungicides available to the organic spinach production community for downy mildew management needs to continue.

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

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.