NOTE: For the disease control products listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, preharvest interval (PHI), restricted entry interval (REI), and special instructions. In many cases, there are other products available with the same active ingredient. Please see Table 25 and Fungicides and Bactericides Alphabetical Listing by Trade Name for more information on products with the same active ingredients.
The symbol OG indicates a product is listed by the Organic Materials Review Institute (OMRI) as approved for use in organic production. See Organic Certification section for more details.
Alternaria leaf spot
Alternaria leaf spot does not affect the root but will reduce the value of fresh-packed plants that retain the foliage. Buy certified disease-free seed or hot-water treat seed. Reduce cruciferous weeds and plow under crop debris in the fall. Rotate with non-cruciferous crops.
azoxystrobin (Quadris): 6.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11. Do not rotate with other strobilurin (Group 11) fungicides.
Bacillus amyloliquefaciens strain D747 (Double Nickel 55OG): 0.25 to 3.0 lb/A; PHI 0d, REI 4h, Group 44. Use sufficient water for thorough coverage. Begin application at crop emergence, transplanting or when conditions are conductive to disease development. Other formulations are available. See label for rates.
Bacillus subtilis Strain QST 713 (Serenade MaxOG): 1.0 to 3.0 lb/A; PHI 0d, REI 4h, Group 44. Begin applications soon after emergence and when conditions favor disease. Apply in sufficient water to provide thorough coverage.
penthiopyrad (Fontelis): 16.0 to 30.0 fl oz/A; PHI 0d, REI 12h, Group 7.
cyprodinil plus fludioxonil (Switch 6.25 WG): 11.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A; PHI 0d, REI 12h, Group 11. Do not alternate with Group 11 fungicides such as Quadris.
Downy Mildew (Hyaloperonospora parasitica)
This disease occurs worldwide, affects most crucifers, and is most important at the seedling stage. It is an important pathogen on radish because it can infect the fleshy root, causing external black patches, lesions on the root shoulder, and internal grey or black flecking and streaking. The root surface is scarred, prone to cracking or splitting, and unmarketable. Manage Downy mildew on transplants by improving air circulation and irrigating early in the day so plants can dry quickly. Plant resistant or tolerant cultivars.
Buy treated seed. Do not use treated seed for food, feed or oil purposes.
azoxystrobin (Quadris): 0.40 to 0.80 fl oz/1000 row feet; PHI 0d, REI 4h, Group 11.
Bacillus amyloliquefaciens strain D747 (Double Nickel 55OG): 0.125 to 1.0 lb/A; PHI 0d, REI 4h, Group 44. See label for at planting instructions and restrictions. Labeled for damping off, seedling blights, and root and crown rot. Other formulations available. See label for rates.
fludioxonil (Maxim 4FS): 0.08 to 0.16 oz/100 lb seed; REI 12h, Group 12. For protection against seed-borne and soil-borne fungi. Does not control Pythium or Phytophthora.
fluopicolide (Presidio): 3.0 to 4.0 fl oz/A; REI 48h, Group 43. For Pythium control applied as banded spray. Application at seeding may help control downy mildew. See label.
mefenoxam (Apron XL): 0.085 to 0.64 fl oz/100 lb seed; REI 48h, Group 4.
mefenoxam (Ridomil Gold SL): 1.0 to 2.0 pt/A; REI 48h, Group 4. Pre-plant incorporated or soil spray broadcast or band).
White Rust, White blister (Albugo candida)
Yield reductions are rare but quality is reduced by the prominent signs of the pathogen. On radish, white rust can also infect flower shoots and cause root swellings. Use resistant cultivars where available and rotate to non-hosts where the disease is common. Proper fertility levels, especially of phosphorous and potassium, have been reported to reduce disease.
azoxystrobin (Quadris): 6.0 to 15.5 fl oz/A; PHI 0d, REI 4h, Group 11. Do not make more than one foliar application of Quadris before alternating with a non-group 11 fungicide.
copper oxychloride plus copper hydroxide (Badge X2OG): 1.0 TO 2.25 lb/A; PHI 0d, REI 48h, Group M1. Begin application when disease first appears or when conditions favor disease.
pyraclostrobin (Cabrio EG): 8.0 to 16.0 oz/A; PHI 0d, REI 12h, Group 11. Do not rotate with other Group 11 fungicides.