Cucumber Downy Mildew in Wooster Sentinel Plot and Fremont Research Plots

Dr. Francesca Rotondo, director of the OSU Plant Diagnostic Clinic, confirmed downy mildew on cucumber in the Wooster (Wayne County)

Downy mildew on cucumbers in the OSU Sentinel plots at NCARS, Fremont, OH, July 24, 2023. Photo by R. Schaffter.

Sentinel plot and in research plots at the OSU North Central Agricultural Research Station (NCARS: Sandusky County) yesterday, July 22. This is the first report of cucumber downy mildew in Sandusky County this year. Cucumber and melon growers in northern and central Ohio counties should apply downy mildew-targeted fungicides (Orondis Opti, Ranman, Omega, Previcur Flex, and Elumin) posted here and here in a spray program alternating fungicides with different modes of action/FRAC group.  Follow all label instructions. Growers in southern Ohio should apply protectant fungicides and ramp up their scouting of cucumber and melon fields.

Bacterial spot on pumpkin – can be mistaken for downy mildew.

Dr. Rotondo also confirmed bacterial spot in the Wooster sentinel plot on pumpkins and squash. Bacterial spot is caused by Xanthomonas cucurbitae, a bacterial pathogen favored by high temperatures and rainy conditions. There are no options for management once the disease is established in the field. Copper compounds may slow epidemic development if applied early and often (see label). The most effective strategy is to use pathogen-free seed. We recommend a simple Clorox seed treatment to sanitize seeds.

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