Cercospora leaf spot is the most common disease that occurs on beets. Circular spots with reddish brown or purplish margins are the first signs. The most common insect pests of beets are aphids, leafminers, flea beetles and webworms. Sanitation and crop rotation should be practiced to avoid pest build-ups. Beets will develop internal black spot if soil boron is not adequate.
Radishes prefer cool and moist conditions for best growth.
The optimum temperature is 50 to 65 F. Optimum soil temperature for seed germination is 45 to 85 F. Radish seed will not germinate when the soil temperature is above 95 F. Spring-planted radishes should be harvested early. High summer temperatures cause radishes to become pithy and develop a strong flavor. Sandy to sandy loam soils are best for radishes. 12 to 24 inches apart and place the seed inch deep with about 1 inch between seeds. Plant every seven to 10 days during the recommended planting periods for a continuous supply of radishes.