Clemson Extension Plant Pathologist Tony Keinath recently released this management guide for Downy Mildew in cucurbits.
Here are the links to the resources referenced in Dr. Keinath’s guide:
- Cucurbit Downy Mildew Alert System
- Southeastern Vegetable Crop Handbook
- The downloadable PDF of this management guide.
Here are a few extra notes from Dr. Keinath:
- Downy mildew fungicides that contain a single active ingredient, such as Ranman, should be tank-mixed with either chlorothalonil or mancozeb. Because Zampro includes Forum, which does not offer much protection as a tank-mix partner, Zampro also should be tank-mixed with a protectant.
- Downy mildew may show resistance to Previcur Flex, Presidio, Tanos, Curzate, or Forum and therefore are not recommended in South Carolina for 2015. If growers want to continue to use these fungicides that they already have on hand, they can be used as long as they are tank-mixed with either chlorothalonil or mancozeb. The protectant fungicide will help control downy mildew that is resistant to one or more of the above fungicides. Based on fungicide sensitivity tests in 2013-2014, there is about a 25% chance that each of these fungicides will not control downy mildew on cucumber.
- If the sample spray schedule is used on pumpkin, fungicides such as Torino and Quintec should be used when powdery mildew appears.