Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu
We began our yearly dissemination of MelCast for watermelons on Friday, June 2.
MelCast is a weather-based spray advisory program for watermelon developed at Purdue University. The program uses hours of leaf wetness and temperature during leaf wetness periods to determine when a fungicide should be applied. Weather information is used to calculate how favorable weather is to the development of gummy stem blight or anthracnose. The output of the program is an “environmental favorability index unit” (EFI) for each day. The EFI values are added together. Once the threshold of 30 EFI is reached, a fungicide application is recommended. After the fungicide application, begin adding the EFI again from zero. If two weeks elapse and you have not accumulated 30 EFI, spray anyway. Also, add 2 EFI for each overhead irrigation event. We currently run MelCast for three locations in Delaware (Coverdale Crossroads, southeast of Laurel, and southwest of Laurel) and five locations in Maryland (Galestown, Hebron, Salisbury, Waldorf and Woodbine). Use EFI values for the location that is nearest to your farm.
To use MelCast on your farm, please call Karen Adams (302-856-7303) or Sheila Oscar (410-742-8788) and give us your name and e-mail address. More details about how the program works are available at our Disease Forecasting Web page, which is at:
http://extension.umd.edu/mdvegetables/vegetable-plant-diseases/disease-forecasting. In addition, we post the MelCast Advisory online three times a week.