Final MELCAST Update

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).

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 2019 season. If you have comments or questions about MELCAST in 2019, let me know. I look forward to working with all of you in 2020.