The National Cucurbit Downy Mildew Forecasting site (Figure 1) has undergone a complete update, and growers requiring alerts will need to re-register. Growers can register for e-mail and/or text alerts when cucurbit downy mildew (CDM) has been found in proximity to their specific farm location. CDM is an aggressive disease that can take crops from vigorous growth to decimated vines in a period of about 2 weeks under rainy conditions. Signing up for alerts helps growers strategize fungicide applications to periods of risk, reducing costs.
Register for Alerts
To sign up for alerts, growers should navigate to the above website, then click the alerts tab. Simple information is entered here to register for alerts. Growers can specify the frequency of their alerts (with the option to choose only the first alert that season; not recommended), choose to be alerted by email or SMS (text message), and whether they are alerted immediately.
Downy Mildew Symptoms & Signs
Cucumbers, squashes, melons, and pumpkins can all be affected by the disease. CDM does not directly affect the fruit, and early symptoms are most apparent on foliage. Initial symptoms are yellowed areas, bordered by leaf veins, which often occur near the stem end of the leaf or along the outer edges. Dark gray sporulation from the downy mildew pathogen will be visible on the undersides of leaves, opposite the yellowed areas. Sporulation is easiest to see if plants are scouted early in the day. CDM spreads quickly during rainy conditions, and entire vines can be destroyed in 10 days if CDM is not managed.
Managing with Fungicides
CDM-specific fungicides are listed in ID-36, the Commercial Vegetable Production Guide. For single mode-of-action products, it is recommended to tank-mix with mancozeb or chlorothalonil for best results. For additional information on selecting CDM fungicides and adjusting your spray program, discuss with your local Extension agent.
- Vegetable Production Guide for Commercial Growers (ID-36)
- IPM Scouting Guide for Common Problems of Cucurbit Crops in Kentucky (ID-91)
- Cucurbit Crops Scouting Guide (mobile Veggie Scout website)
- Cucurbit Downy Mildew Forecasting (ipmPIPE)
By Emily Pfeufer, Extension Plant Pathologist