Irrigation Anything that restricts the rapid growth of radishes results in pithy, cracked, harsh-tasting roots. Ample moisture is the most easily controlled factor in growth. Radishes require 1 inch of water per week. Weed Control Dacthal and Roundup are the only herbicides labeled for use on radishes. Generally, no chemical weed control is used due to the short growing season.
Mechanical cultivation is kept shallow to avoid root damage.
Nematodes Radishes are susceptible to nematode damage. Consult with your county Extension agent about the free nematode assay procedure. Vapam soil fumigant controls nematodes and most other soil-borne pests. Diseases Radishes share many diseases with other members of the crucifer family. Never plant radishes following cabbage, broccoli, greens, turnips, rapeseed, or Chinese cabbage.