Downy mildew was confirmed on cucumber leaves from a commercial farm in Wayne County, OH on Wednesday June 28 and the next day in Monroe County, MI. This follows the first confirmed case in Ontario (Essex County) on June 27.
The OH outbreak was spotted by the Wayne County IPM Scouting team. Northern Ohio cucumber and cantaloupe growers should be scouting fields now and prepare to apply effective fungicides. Rainy and overcast weather favors the movement of the downy mildew pathogen. Although this disease is also favored by cooler weather, it can be serious in hot weather if nights are cool and rainy, overcast conditions persist.
Fungicide recommendations can be found in the June 28 post of Ohio Veggie Disease News and in the Midwest Vegetable Production Guide for Commercial Growers.
Risk is lower for cucumbers and melons in Central and Southern OH, but fields should be scouted often. Risk for squash and pumpkins usually increases in late July/August. Downy mildew was reported this week on squash in southern Kentucky, so we will be keeping an eye on that situation.
Sally A. Miller