Downy mildew was confirmed today on cucumbers in our sentinel plot on the OSU North Central Agricultural Research Station in Fremont and a home garden in Clyde, both in Sandusky County. This follows reports for cucumbers in Medina and Wayne Counties earlier this month. As I’ve indicated in previous posts, we believe that cucumber downy mildew has been present in northern Ohio counties for several weeks; growers should be protecting cucumbers with recommended fungicides. We haven’t had reports of downy mildew on melons (cantaloupe) but melons are susceptible to the strain of the downy mildew pathogen circulating in northern Ohio, as are giant pumpkins. So these crops should also be protected now with fungicides.
While downy mildew does not cause lesions on fruit, it does reduce yield significantly by damaging and eventually killing the foliage. Growers who stop harvesting fields with severe downy mildew should destroy the plants as soon as possible to eliminate this source of inoculum. The pathogen does not survive in the soil.
Home gardeners who choose to treat cucumbers or melons with a fungicide should purchase a product containing chlorothalanil and start applications before the disease appears. If the disease becomes severe gardeners should destroy the plants to reduce local inoculum.