MELCAST Update

(www.melcast.info)

Editor: Cesar Escalante                                                                                                

Extension Plant Pathologist

escalac@purdue.edu

812-886-0198

June 18, 2026

We received heavy rainfall in several parts of Indiana last night. These conditions, combined with the current phenological stage of melons, for example, the dense canopy resulting from active vegetative growth, can create favorable conditions for disease development. Some of the diseases that may appear 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. This is the stage at which preventive management is most effective, and systemic fungicides can play an important role in suppressing pathogen development. Refer to the cantaloupe and watermelon fungicide schedule to learn more about available fungicide options and their recommended use.

For cantaloupe, MELCAST data from June 11 through June 17 suggest maintaining a 14-day fungicide spray interval across all locations. For watermelon, MELCAST data show a similar trend, except in West Lafayette and Wanatah, where conditions from June 11 to June 14 indicated spray intervals of 9 and 12 days, respectively. This suggests that fungicide applications should have been made more frequently at these locations. If applications have not yet been made, growers should apply fungicides as soon as possible to maintain adequate disease protection. Continue to monitor for other common diseases, such as bacterial diseases and Phytophthora. The MELCAST system does not account for these diseases, so pesticide applications should be made promptly if any of these issues are observed in your fields. Information about possible products can be found in the cantaloupe and watermelon fungicide schedule.

Last but not least, I would like to inform watermelon, cantaloupe, and pumpkin growers that my team is conducting a study on the diversity of gummy stem blight pathogens in Indiana. If you suspect gummy stem blight in your fields, please contact me by phone, text, or email. We would appreciate the opportunity to visit your farm and collect samples for this research. The study has two primary objectives: (1) to evaluate the genetic diversity of the gummy stem blight pathogen population in Indiana, and (2) to assess fungicide resistance among pathogen isolates to support more informed fungicide management decisions. I greatly appreciate the support of the Indiana State Department of Agriculture and the Illiana Watermelon Association in making this study possible. Your collaboration and participation are invaluable to the success of this project.

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

Sincerely,
Cesar Escalante
Extension Plant Pathologist