Diseases
Stalk rot (Sclerotinia sclerotiorum)
This disease causes serious loss in the field, storage, under transit and market conditions. The infections begin as circular water soaked areas, which become soft and watery as the disease progresses, and damage the entire cabbage head.
Control: Avoid planting cabbage and other susceptible crops in fields infested with white mold. Mechanical injuries to cabbage heads during harvesting operations should be avoided.
Black rot (Xanthomonas campestris pv. campestris)
The infected tissue turns brown and dies, and severely affected leaves drop off. The infected stems and roots become black. The heads of the infected plants remain small and its quality is reduced making it unfit for consumption.
Control: Avoiding continuous cropping of crucifers in the same field and use of resistant varieties offer good control. Treat the seeds with streptocycline (300 ppm). Weekly application of Pseudomonas fluorescence 2% solution after the head initiation also controls the disease.
Downy mildew (Perenospora parasitica)
Small, light green-yellow lesions on the upper leaf surface, later a grayish white moldy growth is developed on the undersurface of the leaf, and the leaf eventually becomes papery and die. Cabbage heads develop sunken black spots.
Control: Removal of weeds and alternate hosts and spraying with copper oxychloride (0.3%) are effective in controlling the disease.
Leaf spot and blight (Alternaria brassicae and A. brassiciola)
Small dark yellow spots appear on the leaf surface, which later enlarge to form circular areas with concentric rings surrounded by yellow halos. In severe cases, the entire plant defoliates.
Control: Use of disease free seeds, practicing proper crop rotation and seed treatment with hot water (50° C for 30 minutes) helps to minimize the disease incidence.
Yellows or fusarium wilt (Fusarium oxysporum f. sp conglutinans)
Initially the lower leaves and later the upper leaves turn yellow, wilt and die. With time, the dead leaves turn brown and the affected tissue becomes dry and brittle.
Control: Use of resistant varieties and very early sowing of cabbage can minimize the disease incidence.
Black leg (Phoma lingum)
Irregular spots develop on leaves and stem, which extend below the soil surface, causing black rot of lower stem and roots. Severely affected plants remain stunted and finally wilt, and under favourable condition the disease causes severe yield loss.
Control: Use of disease free seeds and hot water treatment of seeds is recommended to control the disease.
Club root (Plasmodiophora brassicae)
Roots of the infected plants develop club like swellings. Plants infected in the nursery get killed, whereas those attacked at a later stage wilt in hot weather but partly recover at night. Finally leaves become stunted, yellowish and prematurely bolt in hot weather.
Control: Crop rotation of more than 6 years and mixing finely ground limestone before planting help to reduce disease incidence. Incidence of this can be managed by weekly hoeing. Drenching with Pseudomonas fluorescence 2% controls the disease.
Damping off (Pythium debaryanum)
Seedlings develop lesion near the collar region and tissue beneath become soft due to which seedling collapse and die.
Control: Seed treatment with Trichoderma viride (3-4 g/kg of seed) and soil drenching with dithane M 45 (0.2%) or bavistin (0.1%) afford protection against the disease.