MSU report: https://www.canr.msu.edu/news/cucumber-downy-mildew-outbreak-of-2020
IPM Pipe map: https://cdm.ipmpipe.org/
Katie Goldenhar, Pathologist-Horticulture
Downy mildew has been confirmed in a pickling cucumber crop in Berrien county, in Southwest Michigan. Growers are advised to use a downy mildew specific fungicide program, if this hasn’t been started.
Cucumber downy mildew has NOT been identified in Ontario, but the risk is high for Ontario, with the confirmation in the Great Lakes Region, humid weather and cool nights.
Trials in Michigan and Ontario have shown that the three most consistently effective downy mildew fungicides are Orondis Ultra, Torrent and Zampro. Where possible, it is important for resistance management to these products to Tank mix each application with chlorothalonil or mancozeb. In addition to tank mixing to delay resistance development, never make back-to-back applications of products from the same chemical family. Follow a 5 to 7-day application interval, and rotation of the three products can be repeated as necessary.
If you suspect downy mildew in your field, send for confirmation immediately. Contact either OMAFRA specialist listed below if you have any questions about detection or management.
Cucumbers are most at risk, but cantaloupe growers should be aware that downy mildew that infects cucumbers is also a risk. See crop labels for listed cucurbit crops registered on the products below.
Katie Goldenhar, Pathologist—Horticulture, katie.goldenhar@ontario.ca, 519-835-5792
Andrew C. Wylie, Vegetable Crop Specialist (A), andrew.c.wylie@ontario.ca, 519-401-5890
