Leaf Spots (Alternaria and Cercospora)
Leaf spot fungi do not infect roots but severe foliar infections can reduce yield and blighted foliage can reduce the value of fresh-packed plants. Hot water seed treatment can eliminate seedborne fungal pathogens but will not protect from airborne inoculum. To reduce infection by airborne inoculum, control weeds to improve airflow and encourage leaf drying, and plow under crop debris promptly in the fall. Practice a 3-year crop rotation out of brassicas.
FRAC Group 7:
- penthiopyrad (Fontelis): 16.0 to 30.0 fl oz/A; PHI 0d, REI 12h.
FRAC Group 9:
- cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
FRAC Group 11:
- azoxystrobin (Quadris F): 6.0 to 20.0 fl oz/A; PHI 0d, REI 4h. Do not rotate with other Group 11 fungicides.
- pyraclostrobin (Cabrio EG): 8.0 to 12.0 oz/A; PHI 0d, REI 12h. Do not rotate with other Group 11 fungicides.
FRAC Group 12:
- cyprodinil plus fludioxonil (Switch 62.5 WG): 11.0 to 14.0 oz/A; PHI 7d, REI 12h, Groups 9 & 12.
FRAC Group BM02:
- Bacillus amyloliquefaciens strain D747 (Double Nickel 55OG): 0.25 to 3.0 lb/A; PHI 0d, REI 4h. Applied as foliar spray. For suppression of Alternaria. See label for application methods and instructions.
FRAC Group M01:
- copper hydroxide (Kocide 3000): 0.5 to 0.75 lb/A; PHI 0d, REI 48h. Turnip greens only.
Black Leg, or Phoma Leaf Spot and Canker (Phoma lingam)
From foliar lesions, the fungal pathogen that causes black leg spreads into leaf veins to the petioles and eventually the main stem. On rutabaga and turnip, a dry rot of the bulb or hypocotyl develops. The neck and shoulder areas develop large, brown lesions, followed by an extensive dry rot deep into the fleshy tissue. Severely affected bulbs become shriveled and dry and are often invaded by secondary fungal and bacterial decay organisms. Start with certified or treated seed or treat seed with hot water or fungicides. Rotate out of brassicas for 4 years. Promptly incorporate infected crop debris after harvest. Eliminate brassica weeds, which can act as hosts. Apply foliar fungicides to protect susceptible cultivars (see above).
Seed Decay and Damping-Off
Damping-off diseases are favored by cool, cloudy weather, wet and/or compacted soils, high humidity, and overcrowding. Plant into well-drained and well-fertilized soil when conditions are conducive to fast germination and growth. Avoid excessive irrigation.
FRAC Group 4:
- mefenoxam (Ridomil Gold SL): 1.0 to 2.0 pt/A; REI 48h. Pre-plant incorporated or soil spray broadcast or band.
FRAC Group 7:
fluopicolide (Presidio 4SC): 3.0 to 4.0 fl oz/A; REI 12h. Apply for Pythium root rot control as banded spray. Do not use on varieties of turnips such as fodder turnips intended for livestock use. See label for additional restrictions.
FRAC Group 11:
- azoxystrobin (Quadris F): 0.4 to 0.8 fl oz/1000 row ft.; PHI 0d, REI 4h. For Rhizoctonia root rot control applied as in-furrow application. See label for restrictions.
FRAC Group 12:
- fludioxonil (Maxim 4FS): 0.08 to 0.16 fl oz/100 lb seed; REI 12h. For protection against seedborne and soilborne fungi. Does not control Pythium or Phytophthora. Use as seed treatment prior to seedling.
FRAC Group 22:
- ethaboxam (Elumin): 8.0 fl oz; PHI 2d, REI 12h. Labeled for Pythium damping-off of turnip greens.
FRAC Group BM02:
- Bacillus amyloliquefaciens strain D747 (Double Nickel 55OG): 0.125 to 1.0 lb/A; PHI 0d, REI 4h. See label for application methods and instructions.
White Rust (Albugo candida)
Yield reductions caused by white rust are rare, but quality is reduced by the raised white spore masses of the leaf undersides of the pathogen. Use resistant cultivars where available and rotate to non-hosts where the disease is common. Proper fertility levels, especially of phosphorus and potassium, have been reported to reduce disease.
FRAC Group 11:
- azoxystrobin (Quadris F): 6.0 to 20.0 fl oz/A; PHI 0d, REI 4h. Do not alternate with another Group 11 fungicide.
- pyraclostrobin (Cabrio EG): 8.0 to 16.0 oz/A; PHI 0d, REI 12h. Do not rotate with other Group 11 fungicides.
FRAC Group M01:
copper oxychloride plus copper hydroxide (Badge X2OG): 1.0 to 2.25 lb/A; PHI 0d, REI 48h.