Agricultural crops :: Oilseeds :: Sunflower
Alternaria Blight : Alternaria helianthi
Symptom |
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The disease is a destructive one, widely distributed wherever the crop is grown.
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Severe reduction in seed and oil yield reported.
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The most affected components are number of seeds per head and the seed yield per plant.
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The disease also affects the quality of sunflower seeds by affecting germination and initial vigour of the seedlings.
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The disease is characterised by the development of dark brown to black, circular to oval spots varying from 0.2 to 5 in diameter.
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The spots are surrounded by necrotic chlorotic zone with grey white necrotic centre marked with concentric rings.
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Spots first appear on lower leaves, later spread to middle and upper leaves.
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At later stages, spots may be formed on petioles, stem and ray florets.
Management
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Occurrence and severity of the disease depends on the season and planting dates.
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Mid-September planting of sunflower remains free from the disease.
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Foliar spray with 0.3 per cent Mancozeb four times at an interval of 10 days controls the disease.
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