Sally Miller, Melanie Lewis Ivey and Fulya Baysal-Gurel, The Ohio State University Dept of Plant Pathology
Downy mildew was confirmed on cucumber samples from Wayne and Ashland counties in Ohio on July 6. This follows closely on the July 5 report of downy mildew in cucumbers Chatham-Kent, Ontario, where initial symptoms were observed as early as June 30 (see http://cdm.ipmpipe.org). The spread of downy mildew in Ohio is dependent on the weather - bright sunny days are detrimental to spore survival and transport, while overcast days promote spore survival and rainfall results in spore deposition.
--Rick VanVranken For Ohio's management recommendations...
Suggested downy mildew management programs for cucumbers:
Fungicide application:
Protection before disease appears: Apply one of the following fungicides on a 7-10 day schedule, tank mixed with Bravo, Manzate or Dithane: Presidio, Ranman, Previcur Flex, Tanos, Curzate or Gavel (Gavel already contains mancozeb). Alternate products. The application interval can be lengthened under dry conditions. Use the shorter interval under cool, moist conditions.
Management after disease appears: Apply one of the following fungicides on a 5-7 day schedule, tank mixed with Bravo or Dithane: Presidio, Ranman, Previcur Flex, or Tanos. Alternate products. The application interval can be lengthened under dry conditions. Use the shorter interval under cool, moist conditions. See product labels for fungicide rates.
Most recent research has shown that fungicides can be ranked as follows for efficacy against downy mildew: Presidio = Ranman > Previcur Flex > Curzate > Gavel > Mancozeb = Bravo.
Note that the fungicides recommended above have different preharvest intervals (PHI). Keep this in mind when fungicides are applied after harvesting begins.
| Product | PHI (days) |
| Bravo Weather Stik | 0 |
| Ranman | 0 |
| Previcur Flex | 2 |
| Tanos | 3 |
| Dithane or Manzate* | 5 |
| Gavel* | 5 |
| Presidio | 2 |
| Curzate | 3 |
