Diseases Management in Onion
Small white sunken lessions with purple centre appears on leves and they enlarge rapidly, girdling the leaves and flower stem which fall over and the bulb decay follows in the storage.
This disease can be controlled by spraying the crop with one per cent Bordeaux mixture or Mancozeb (Dithane M-45) @. 2.5 gm per liter of water or Copper Oxychloride (Blitox-5Q) @ 5.0 mg per liter of water.
2) Onion Smut:
Uracystis cepulae Frost.
Dark, slightly thickened area appears on cotyledon of young seedlings with numerous raised blisters near base of scales of older plants, which on rupturing expose black and powdery mass of spores.
The disease can be controlled by seed treatment with Thiram @ 45 gm for 0.45 kg of seed (Larson and Walker, 1953) .and spraying formaldehyde solution in the furrow.
3) Base Rot:
Fusariwn oxyspomtn Schtecttt.
It is due to this disease that yellowing and drying back from the tip of leaves occurs. The serial parts of the disease affected plants may die in one or two weeks or decay may extent over a much longer time.
i. Crop rotation with plants not affected by this fungus may help to control this disease.
ii. Spraying the crop with Mancozeb (Dithane M-45) @ 2.5 gm per liter of water may reduce the incidence of this disease.