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, days to harvest (dh), REI, and special instructions. In many cases, there are other products available with the same active ingredient. Please see Table 28 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.
Leaf Spots (Alternaria and Cercospora)
Leaf spot fungi do not infect the root but infection can reduce yield, and blighted foliage can reduce the value of fresh-packed plants. To help reduce leaf spot, buy hot-water treated seed, reduce weeds and plow under crop debris in the fall.
azoxystrobin (Quadris): 6 to 15.5 fl oz/A. (0 dh, REI 4h, Group 11). Do not rotate with other Group 11 fungicides.
copper hydroxide(Kocide 3000): 0.5 to 0.75 lb/A. (0 ph, REI 48h, Group M1. Not labeled for rutabaga.
cyprodinil plus fludioxonil (Switch 6.25 WG): 16.0 to 30.0 oz/A. (7 dh, REI 12h, Groups 9 & 12).
penthiopyrad (Fontelis): 11.0 to 30.0 fl oz/A. (0 dh, REI 12h), Group 7).
pyraclostrobin (Cabrio EG): 8 to 12 oz/A. (0 dh, REI 12h, Group 11). Do not rotate with other Group 11 fungicides.
Black Leg (Phoma Leaf spot and canker)
From foliar lesions, the pathogen spreads into leaf veins to the petioles and eventually the main stem. On root crops, such as rutabaga and turnip, a dry rot of the bulb or hypocotyl develops. The neck and shoulder areas have large, brown lesions, and an extensive dry rot deep into the fleshy tissue develops. Severely affected bulbs become shriveled and dry, and are often invaded by secondary fungal and bacterial decay organisms. Start with certified disease-free seed or treat seed with hot water or fungicides. Rotate to non-susceptible crops. Promptly incorporate infected crop debris after harvest. Apply foliar fungicides to protect susceptible cultivars (see above).
Seed Decay and Damping-Off
Buy treated seed. Do not use treated seed for food or feed.
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.
mefenoxam (Apron XL): 0.085 to 0.64 fl oz/100 lb seed. (REI 48h, Group 4). For Pythium damping-off protection.
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. (0 dh, REI 4h, Group 11). Do not alternate with another Group 11 fungicide.
pyraclostrobin (Cabrio EG): 8.0 to 16.0 oz/A. (0 dh, REI 12h, Group 11).