Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu
Late blight on tomato was identified in a backyard garden near Ellendale in Sussex County this week. Conditions have been favorable lately for late blight. Commercial tomato growers should be including a late blight specific fungicide in their fungicide rotation. Previcur Flex plus Bravo, Tanos, Ranman, or Forum could be used. Check label for specific information and all should be tank mixed with a protectant fungicide. Potatoes are rapidly reaching maturity and late blight should not be an issue at this stage of the season. Organic growers only have copper as a fungicide choice which is not very effective. If backyard tomatoes are badly infected the best control measure is pull them up, place them in sealed plastic bags and dispose of them. Do not put them on a compost pile. Backyard tomato growers have several protectant fungicides that can be used namely mancozeb and products containing chlorothalonil or Daconil. Sprays should be applied at 5 to 7-day intervals before symptoms appear.
Late blight on the underside of a tomato leaf. Note the white cottony growth on the dying tissue.