MELCAST 2017 – Vegetable Crops Hotline


Many cantaloupe and watermelon growers have transplanted seedlings to the field. Soon, these growers will have questions about what and when to apply fungicides. The article below in this issue of the Vegetable Crops Hotline will address what fungicides to apply (Fungicides schedules for cucurbits). This article discusses when to apply fungicides with the MELCAST system.

MELCAST (MELon disease foreCASTer) is a weather-based disease-forecasting program for cantaloupe and watermelon growers developed By Dr. Rick Latin at Purdue University. Instead of using a calendar based fungicide application program where one applies fungicides every 7 to 14 days, the MELCAST program lets growers apply fungicides when the weather is most conducive to disease. The diseases for which MELCAST may be used for are: Alternaria leaf blight, anthracnose and gummy stem blight. Details are listed below or in the extension bulletin, Foliar Disease Control Using MELCAST, BP-67-W. Download the bulletin at http://www.extension.purdue. edu/extmedia/BP/BP-67-W.pdf or contact Dan Egel for a copy. The MELCAST program uses weather information from one of the 13 sites located around Indiana: Battleground, Daviess County, Decker, Elkhart County, Gibson County, Jackson County, Oaktown, Richmond, Rockville, Sullivan, SW Purdue Ag Center, Vincennes, and Wanatah. Cantaloupe and watermelon growers who want to use MELCAST should farm within about 50 miles of a MELCAST site. Cantaloupe and watermelon growers using MELCAST apply foliar fungicides every 14 days unless the weather thresholds described below indicate that an application should be made sooner. Below find more details.

  1. Apply the initial fungicide application at or before vines touch within a row.
  2. Check the Environmental Favorability (EFI) value for the day of fungicide application.
  3. Calculate the threshold for the next application by adding 20 (cantaloupe) or 35 (watermelon) to the EFI value in step 2. To get a MELCAST calendar to keep track of EFI values, call Dan Egel. Alternatively, a MELCAST spreadsheet can be downloaded from
  4. Apply the next fungicide application 14 days after the first, or sooner if the EFI threshold has been reached.
  5. Check the EFI values on the day you make your next fungicide application and re-calculate the threshold for the next application.

A few things to remember: It is best to apply fungicides before the threshold has been reached rather than wait until after the threshold has been exceeded. So, for example, if you are a watermelon grower, the EFI threshold has reached 33 and a rain is expected soon, then go ahead and apply a fungicide. Use the thresholds of 20 and 35 EFI values as guides. Use a lower threshold if you feel that disease pressure is high. Finally, note that fungicide applications for downy mildew and powdery mildew cannot be scheduled with MELCAST.

Keeping track of MELCAST values is similar to keeping track of oil changes in a car or truck. When one changes oil, the mileage is written down and the oil is changed again at the next threshold (3,000 miles or 35 EFI values). EFI values, like mileage of a truck, continue to increase. Check EFI values by using the toll-free phone number 800-939-1604 Monday though Friday; check the website 7 days a week and/or sign up for the free MELCAST Update that comes once a week during the season. Please call Dan Egel with any questions.



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