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2022, Issue 14

Final MELCAST Update

Relatively dry weather over much of the state has resulted in low disease pressure. The rise in MELCAST values in the table below has been modest. Only one cantaloupe site has an estimated spray interval of less than 14 days—Merom Station is at 12.7 days. 

As cantaloupe and watermelon growers approach Labor Day, many will be contemplating the final fungicide application of the season. When should the last spray happen?

In most cases, the last fungicide application should occur 10 to 14 days from the final harvest. Most fungicides that are designed to protect the foliage will last on or in the plant for 10 to 14 days. In addition, diseases such as downy mildew, gummy stem blight or powdery mildew that do not affect fruit directly are not necessary a few days from harvest. A fungicide application a few days before harvest is expensive and ineffective. Plus, it is necessary to keep in mind the Pre-Harvest Interval (PHI). Note—downy mildew has not been reported in Indiana in 2022. 

Some diseases affect the fruit directly. These diseases include anthracnose and Phytophthora blight. However, even for these diseases, most final fungicide applications should occur no sooner than 7 days before harvest. Both anthracnose and Phytophthora blight usually cause lesions on the bottom of the fruit. Such lesions result from spores that splash from leaves. It is difficult if not impossible to coat the bottom of the fruit with fungicide. Instead, the idea is to protect the foliage so fewer spores splash from foliage to fruit.

This is the final MELCAST Update of the 2022 season. If you have comments or questions about MELCAST in 2022, let me know. I look forward to working with all of you in 2023. 

Cantaloupe Slices

Watermelon Slices

EFI Values for
Cantaloupe EFI Watermelon EFI Total Precip High Temp Total GDD Cantaloupe Spray Interval (in days) Watermelon Spray Interval (in days)
11-22 180 (0) 267 (0) 30.11 55 3719 14.0 14.0
11-21 180 (0) 267 (0) 30.11 49 3717 14.0 14.0
11-20 180 (0) 267 (0) 30.11 33 3717 14.0 14.0
11-19 180 (0) 267 (0) 30.11 32 3717 14.0 14.0
11-18 180 (0) 267 (0) 30.11 31 3717 14.0 14.0
11-17 180 (0) 267 (0) 30.11 34 3717 14.0 14.0
11-16 180 (0) 267 (0) 30.11 34 3717 14.0 14.0
* GDD and Precip data begins on January 1, 2022
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Department of Botany and Plant Pathology at Purdue University Administration
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