MELCAST Update

(www.melcast.info)

Editor: Cesar Escalante                                                                                                

Extension Plant Pathologist

escalac@purdue.edu

812-886-0198

June 25, 2026

(Note: part of this article was published in the Vegetable Crops Hotline Newsletters - Issue 773)

We have received heavy rainfall in recent days across several parts of Indiana. These conditions, combined with the current growth stage of melons (for example, the dense canopy resulting from active vegetative growth) can create favorable conditions for disease development. Diseases that may become problematic under these conditions include gummy stem blight and anthracnose.

Consider applying systemic fungicides as a preventive measure. Remember that many diseases have latent periods during which no symptoms are visible; however, the pathogen may already be actively colonizing and infecting plant tissues. Preventive management is most effective during this stage, and systemic fungicides can play an important role in suppressing pathogen development. Refer to the cantaloupe and watermelon fungicide schedule for information on available fungicide options and their recommended use.

Continue to monitor fields for other common diseases, including bacterial diseases and Phytophthora blight. The MELCAST system does not account for these diseases, so fungicide applications should be made promptly when they are detected. Phytophthora blight affects cucurbit crops differently. In watermelon, the disease primarily affects fruit, whereas in pumpkins both foliage and fruit may be affected. To protect watermelon fruit, fungicide applications are recommended beginning at the softball stage. In pumpkins, fungicide applications can begin when plants reach the bushy growth stage. Applications may be continued on a weekly or biweekly schedule, depending on weather conditions.

Remember that Phytophthora capsici thrives under warm, wet conditions. The disease is often more severe in low-lying areas of fields that remain saturated for extended periods or have poor drainage. These areas should receive special attention, as they are often the first locations where Phytophthora blight becomes a significant problem. For a complete list of fungicides recommended for managing the diseases discussed in this article, consult the Midwest Vegetable Production Guide. You may also refer to the fact sheet Managing Phytophthora Blight of Cucurbits for a comprehensive list of fungicide options and cultural practices for managing Phytophthora blight.

If you have any questions or comments, please feel free to reach out.

Sincerely,
Cesar Escalante
Extension Plant Pathologist