Cucumbers, melons, squash, and tomatoes are among the most widely grown vegetables in Kentucky, and as many experienced growers can tell you, nothing can bring an untimely end to the season quite like cucurbit downy mildew (Figure 1) or late blight (Figures 2 & 3). These diseases are caused by oomycete pathogens that arrive without much notice, move quickly through a field, and spread rapidly to other farms.
Both diseases are closely tied to weather events occurring to the south of us that spread pathogen inoculum to Kentucky. Cucurbit downy mildew and late blight are most effectively managed with proactive oomycete fungicide programs that can quickly become expensive.
The Cucurbit Downy Mildew ipmPIPE (Figure 4) and the USAblight website (Figure 5) are free, Extension-based resources to aid growers in their fight against disease losses.
These two websites are updated daily, and feature timely information for prevention and management of cucurbit downy mildew or late blight of tomato and potato. A few of the websites’ most helpful features are:
- Sign-up to receive alerts (e-mail or text message) for new, confirmed outbreaks close to your farm
- Monitor estimated threats and risk with disease forecast models
- Utilize additional links for disease information and identification
- Review reports from previous years
Current Kentucky Situation
On July 20 and 21, downy mildew was identified on cucumber in Kentucky (Fayette and Adair counties, respectively). While late blight has not currently been reported in Kentucky, it has been identified in Tennessee.. Thus, growers are encouraged to apply an oomycete-targeted fungicide to all cucurbits. A well-timed, oomycete-targeted fungicide spray in high-risk areas can make a substantial difference in disease management. These include fungicides in FRAC groups 4, 21, 22, 27, 28, 40, and 43; always double-check the label for details on appropriate use and pre-harvest intervals. By using the Cucurbit Downy Mildew ipmPIPE and the USAblight website, growers can stay a step ahead of these aggressive plant diseases.
- Cucurbit Downy Mildew ipmPIPE
- USAblight Website, USDA
- Foliar Diseases of Cucurbits (PPFS-VG-10)
- Late Blight of Tomato (PPFS-VG-13)
By Kimberly Leonberger, Extension Associate, and Emily Pfeufer, Extension Plant Pathologist
The authors thank Brenda Kennedy, Plant Disease Diagnostician for her helpful comments and review.