We have yet to see downy mildew on cucurbits here in Louisiana this year, but it was recently reported on cucumbers in Baldwin County, Alabama, which is east of Mobile Bay. Growers, especially those growing watermelons and pumpkins, and county agents in the Southeast Region of Louisiana should be on the alert and prepared to spray fungicides should it arrive here. Although it does not attack the fruit, it can defoliate these crops exposing the fruit to sunburn. See page 185 of the 2012 Southeastern U.S. Vegetable Crop Handbook (http://www.thegrower.com/south-east-vegetable-guide/) for information on fungicides used to control this disease.
Donald M. Ferrin, Ph.D., Louisiana State University Agricultural Center, Baton Rouge, LA