Onion Smut:
The disease occurs in areas where temperature remains below 30°C. Since the fungus remains in soil, disease appears on the cotyledon of the young plant soon after it emerges. Smut appears as elongated dark, slightly thickened areas near the base of seedlings. The black lesions appear near the base of the scales on planting. The affected leaves bend downwards abnormally. On older plants, numerous raised blisters occur near the base of the leaves. The lesions on plants at all stages often expose a black powdery mass of spores.
Control:
Treating the seeds with Captan or Thiram (2.5g/kg of seed) before sowing controls the disease. Seed bed treatment with Methyl Bromide (1 kg/25 m2.) is effective in controlling the disease.
Head Borer:
The head borer is a serious pest of onion seed crop in Northern India. The larva of this insect cuts the pedicel of the flower and feeds on the stalk. Single larva damages many flower stalks. The fully-grown larva is greenish with dark brown grey lines along the side of the body and measures about 35-45 mm in length.
Control:
Spraying Endosulfan (2-3 ml/litre of water) along with stickers (Triton/ Sandovit) is recommended to control the insect.
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