Major Turnip diseases are:-
1.Alternaria Leaf Spot (Alternaria spp.)
The pathogen affects leaves, stem, pods and seeds. Symptoms of the disease first appear on the leaves of seed stem in the form of small, yellowish, slightly raised lesions. Lesions appear later on the stems and seed pods. Infection spreads rapidly during rainy weather, and the entire pod may be so infected that the styler end becomes black and shrivelled. The fungus penetrates in pod tissues, ultimately infecting the seeds. The infected seed fails to germinate.
Though hot water treatment of the seed kills the fungus, use of diseases- free seeds is recommended. Regular spraying with Difolatan (0.3%) or Dithane M 45 (0.2%) or Ridomil (0.1%) controls the disease effectively.
The disease is transmitted by jassid Orosius albicinctus. The diseased plant assumes a dull grey to light violet colouration. The symptoms of the disease appear at the time of flowering when all the floral parts become green violet and leafy. The sepals and petals become green thick knob headed leaves. Generally, the whole plants show symptoms of the disease. If the infection occurs at an early stage of growth in the nursery then the whole plant is affected.
One or two sprays of Monocrotophos (0.05%) or Phosphamidon (0.05%) or Oxydemetan Methyl (0.02%) is done to eradicate the jassids – the vector of the virus. Soil application of Thimet 10-G (1.5 kg a.i./ha) is also recommended. The application of Thimet should be followed by irrigation. Turnip Crinkle
The disease is characterised by crinkling of leaves. The infected leaves show rugged, appearance, develop yellow patches and are brittle. The yellow patches coalesce and become necrotic with age of the plants. Later on, the affected leaves begin to die and wither away. Severely affected plants show a stunted growth with a rosette appearance.
Losses can be reduced by the use of resistant varieties; adopting sanitary measures including the eradication of susceptible weeds and susceptible volunteer crop plants from a previous planting.
- National Horticulture Board