MELCAST Update

(www.melcast.info)

Editor: Cesar Escalante                                                                                               

Extension Plant Pathologist

escalac@purdue.edu

812-886-0198

July 02, 2026

Recent weather patterns have led to varying disease risk levels across Indiana. For cantaloupe, most locations remain at relatively low risk, with recommended fungicide spray intervals of approximately 14 days. The notable exception continues to be Ft. Vallonia, where disease-favorable conditions have reduced the suggested spray interval to about 10 days. Vincennes also remains somewhat elevated, with a recommended interval of approximately 13 days.

Disease risk for watermelon is generally higher than for cantaloupe across much of the state. The shortest recommended spray intervals are currently in southern Indiana, where conditions suggest that Ft. Vallonia remains with an estimated spray interval of 7 days. Decker, Starlight, Merom Station, Oaktown, Vincennes, Purdue Ag Center, and Washington all have recommended intervals of approximately 9 days or less. Northern Indiana locations, including Goshen and LaGrange, continue to experience suggested spray intervals remaining at 14 days.

Growers should remember that MELCAST recommendations are intended to supplement regular field scouting and should be integrated with crop growth stage, disease history, and weather forecasts when making fungicide decisions.

I have recently observed Alternaria leaf blight in melon research plots at the Southwest Purdue Agricultural Center. In addition, Alternaria has been confirmed in commercial melon fields in southern Indiana. Alternaria symptoms can be easily confused with anthracnose. Both diseases may cause leaf lesions and a "shot-hole" appearance as infected tissue falls out of leaves. Alternaria lesions are typically round, and under severe disease pressure large portions of the foliage may become blighted.

Several fungicides commonly used for anthracnose and gummy stem blight management also provide activity against Alternaria. Products that are effective against Alternaria include Inspire Super, Luna Experience, and Switch. Growers should consult the Midwest Vegetable Production Guide for Commercial Growers for a complete list of recommended products and efficacy ratings.

If you have any questions or comments, please feel free to reach out.

Sincerely,
Cesar Escalante
Extension Plant Pathologist