The \"worms\" are larvae from a flying insect that lays eggs on the tops of the radishes. Next spring try covering the newly seeded bed with Reemay or agricultural fleece to keep the tiny flies from landing on the seedlings. Rotate your crops and do not plant radishes in the same spot. You can also try growing them in a container of potting soil to keep the larvae already in the soil from overwintering and infecting the radishes year after year. Good luck, Marianne Binetti