Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
In addition to MELCAST for Watermelon, we have two models that are designed to help you make spray-timing decisions on diseases of cantaloupe and tomato. MELCAST for Cantaloupes is a fungicide application program for Alternaria leaf blight. It can be used by anyone growing a powdery mildew resistant variety, such as Athena. To use MELCAST for Cantaloupe, apply the first fungicide spray when the cantaloupe vines meet within the row. Additional sprays should be applied using MELCAST. Accumulate EFI (environmental favorability index) values beginning the day after your first fungicide spray. Apply a fungicide spray when 20 EFI values have accumulated by the weather station nearest your fields. Add 2 points for each overhead irrigation. After a fungicide spray, reset your counter to 0 and start over. If a spray has not been applied in 14 days, apply a fungicide and reset the counter to 0 and start over.
TOMCAST is a spray forecaster for leaf blights and fruit diseases of processing tomato. However, it does not work for bacterial diseases or for late blight. In fields that were not rotated away from tomatoes and in late-planted fields begin sprays shortly after transplanting. In all other areas begin sprays when crown fruit are a third their final size. Additional sprays can be scheduled using TOMCAST. Sprays should be applied after accumulating 18 DSVs (disease severity values) since the last fungicide application. Scout fields for bacterial diseases and late blight. If bacterial speck or spot or late blight occurs additional sprays are warranted (see Delaware Extension Bulletin 137 or Maryland Extension Bulletin 236: Commercial Vegetable Production Recommendations).
These disease models are available at http://mdvegdisease.umd.edu/forecasting/index.cfm. In addition you can receive the models by e-mail or fax. Everyone who received the models last year is automatically signed up. To change the way you receive the information or to sign up, please call Jeri Cook at (410) 742-8788.