Foliage and Leaf Problems
Holes from insect feeding
No treatment normally required. Use row cover over emerging seedlings until the plants are large enough to withstand beetle damage or until beetle numbers abate.
Yellow or brown areas accompanied by white mold
Downy Mildew (Peronospora parasitica), a fungal disease that develops during cool most conditions.
Avoid shaded plantings
Purple or black root
Black Root (Aphanomyces raphani), a fungal disease which causes the radish skin to turn purple or black in a single area. As the infection progresses, the entire root may be girdled.
Avoid warm weather plantings, and storage conditions.