MELCAST 2022 – Vegetable Crops Hotline


MELCAST is a weather-based disease-forecasting program that helps growers schedule foliar fungicide applications for watermelon and cantaloupe. MELCAST stands for MELon disease for CASTer. This program, designed by Dr. Rick Latin, Emeritus Professor of Plant Pathology at Purdue University, keeps track of weather conditions so that cantaloupe and watermelon growers can apply foliar fungicides to their crops when they are most needed. The foliar diseases that MELCAST was designed for are Alternaria leaf blight, anthracnose and gummy stem blight. In a typical year, MELCAST will save growers 2 to 3 foliar applications of fungicides without sacrificing yield. MELCAST works by having growers apply fungicides at specific Environmental Favorability Index (EFI) values instead of using a calendar-based schedule. The extension bulletin “Foliar Disease Control using MELCAST” BP-67 describes this program in more detail.

To use MELCAST, follow these steps:

  1. Apply your first foliar fungicide application when vines first touch within a row or earlier.
  2. Find a MELCAST site near your farm from the table below. Select a MELCAST site near enough that the weather is similar to your field.
  3. Use the table at to find the EFI MELCAST value for your site and write down the value on the date when the first fungicide was applied on your MELCAST Record Sheet (contact me for a hard copy). Note that the EFI values are cumulative.  That is, the values keep increasing.
  4. It is not necessary to read the MELCAST EFI values every day. Keep in mind, however that cantaloupe growers will apply a foliar fungicide again at 20 EFI values and watermelon growers will use a 35 EFI threshold. So, when the EFI values are close to the threshold, watch the MELCAST EFI values closely.
  5. When the EFI threshold has been reached or is close for your site, apply a foliar fungicide and write down the new EFI value for the date when the spray was made. If at all possible, do not let the EFI values go over the threshold. It is better to apply a fungicide before the threshold is reached than to wait until the threshold has gone over.
  6. If 14 days have expired and the threshold has not been reached, apply a foliar fungicide. This is because after 14 days, new growth will have occurred and some of the products applied 14 days ago will have weathered. Again, when the next fungicide application has been made note the EFI value.

Using MELCAST is much like keeping track of the mileage for oil changes in your truck. Note the accumulated EFI values when you make your first spray much as you would write down the mileage on your truck when you change the oil. Make your next spray when the EFI threshold nears the threshold by keeping track of the accumulating EFI values much as you would change the oil in your truck every 4,000 miles.

If you choose to view MELCAST information on the Internet, go to  You will see a table with several MELCAST sites around Indiana as well as in other states. The table also has more detailed information about each MELCAST location. Click on the location nearest your farm.

Information at each location includes EFI’s for cantaloupe and watermelon for the past 7 days, total precipitation, high temperature and growing degree days. Below the table is a link for the past week’s data and the state summary.

If the Indiana state summary is chosen, all the Indiana MELCAST sites can be viewed along with the EFI values for the past 7 days and, a 14-day EFI total for each site.  All EFI values are updated on the Internet 7 days a week. Plus, on the state summary page, a weather summary may be found and a paragraph about pest information.

It is possible to sign up for a free hard copy of the weekly MELCAST Update newsletter (during the season) by contacting Dan Egel.

A list of all the MELCAST sites can be found below.

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