Downy mildew was confirmed this afternoon in cucumbers in West Salem (Wayne County), OH. This follows a report of downy mildew on pickling cucumbers and cantaloupe in Essex County, Ontario yesterday, and is about 8 days earlier than our first Ohio report in 2016. Cucumber and melon growers throughout Ohio should intensify scouting, and these crops should be protected with effective fungicides. Cooler, wetter conditions the last week have been very favorable for downy mildew. In northern Oho counties, the downy mildew risk is high, so the more effective downy mildew fungicides Ranman 400SC and/or Orondis Opti A & B (co-pack) should be the core of the fungicide program. Zing!, Gavel, Zampro or other fungicides (see table below) can be rotated into the program. A chlorothalanil (Bravo, Echo, Equus, Initiate) or mancozeb (Dithane, Manzate, Penncozeb) product should be tank mixed with the downy mildew fungicide. Always rotate fungicides with different modes of action and follow label instructions. Remember that Orondis Opti A & B applications are restricted to 1/3 of the total fungicide applications. We recommend applying the first Orondis application when the risk of downy mildew is highest. Under highly conducive environmental conditions, apply fungicides on a 5-7 day schedule. When the risk is lower due to hot, dry, sunny weather, or downy mildew has not been reported in the area, the schedule may be stretched to 7-10 days. Cucumber and cantaloupe downy mildew risk is much higher in northern than in central and southern Ohio at this time.
Thanks to Chris Smedley and the Wayne County IPM scouting program for bringing this sample to us for confirmation.