Taking an environmentally sensitive approach to pest management


Missouri Produce Growers


Zelalem Mersha
Lincoln University Cooperative Extension
Plant Pathology

MELCAST - what is it and how to use it

Zelalem Mersha
Lincoln University Cooperative Extension

Published: July 1, 2013

(Editor's note - this continues a short article from the April edition.)

MELCAST - What for? MELCAST is a spray-advisory program to control Alternaria leaf blight, Anthracnose and Gummy stem blight diseases on watermelon and cantaloupe. It is NOT applicable to any other diseases like Bacterial blotch and Powdery Mildew. For more than 10 years, the system has been tested in different parts of the country and helped farmers to save 1-2 sprays of fungicides per season.

MELCAST - how does it work? In simple terms MELCAST advises farmers to start the first spray when the vines touch within a row and to continue their spray plans based on environmental favorability in that particular location. If you live within a 20-25 miles range of the four locations in Missouri, you would be able to get a value which technically is referred to as Environmental Favorability Index (EFI). To learn more about using the MELCAST system and how to access the data please contact Zelalem Mersha (mershaz@lincolnu.edu, 573-681-5634), Sarah Denkler (denklers@missouri.edu, 573-686-8064) or visit the following website to get an update of the EFI values (http://btny.agriculture.purdue.edu/melcast/).

What is an EFI value? This is a value developed through many years of experimentation at Purdue University. These studies have developed models which assign a daily value in the scale of 1 (not favorable) to 10 (highly favorable) for a given location, at a particular time based on the prevailing weather. Growers will sum up these EFI values over a certain number of days to make an informed decision when to spray.

What are the rules to spray? The principles of the MELCAST's spray plan work similar to the mileage based service or oil change of our cars.

  1. Start to spray at or before the vine-touch with in a row and record the EFI value for the day that the fungicide was sprayed.
  2. Calculate the threshold for the next spray by adding 20 (for Cantaloupe) or 35 (for Watermelon) EFI values to what was recorded in step 1, and then spray your next fungicide.
  3. Make your next fungicide application based on the 20 or 35 EFI cumulated values. If the thresholds are not reached within 14 days after step 2, then spray your field.
  4. Recalculate the EFI value based on the thresholds and continue the spray plan until the end of the season. Keep in mind the 14-days interval if the thresholds are not achieved.
  5. Make sure to follow the REI (Re-entry Interval) and PHI (Pre-harvest interval) of the fungicides in your spray plan to decide when to re-enter your field or to harvest your crop, respectively. For the comprehensive list of fungicides, please refer the Midwest Vegetable Production Guide 2013. You can either buy the book or download the electronic version from http://www.btny.purdue.edu/pubs/id/id-56/ or .

To read more about MELCAST and other disease management topics on horticultural crops, visit the website: http://www.extension.purdue.edu/extmedia/BP/BP-67-W.pdf.

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REVISED: November 24, 2015