Ramularia leaf spot of rhubarb

Leaf infection with Ramularia rhei appears first as small red dots that gradually enlarge to form circular lesions a half-inch or more in diameter. Larger spots become white to tan with purplish halos. The larger spots turn tan in color and become sunken lesions in the stalk tissue. Stalk infections occur later, appearing as small spots that elongate as the stalk grows. White fungus develops in the centers of spots on both leaves and stalks, becoming brown as the tissue dies. Stalk infection is a key symptom of ramularia infection.