Sunflower necrosis disease
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A short duration pulse crop may be planted during the months of June and August
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DISEASE IN sunflower as necrosis (black burning) begins from the margin of the leaf and extends to the growing tip. The plants remain stunted or die prematurely.
The infection may occur at any stage of crop. Plants infected prior to flowering remain sterile.
Apart from necrosis symptoms, mosaic symptoms are also seen on the leaves.
Sometimes the stem below the head bends into `S' shape. Plants infected at grain filling stage exhibit necrosis below the head.
Alternate host
Seeds from infected plants are found chaffy. The disease is transmitted through thrips.
The obnoxious weed Parthenium is suspected as alternate host, as its pollen is known to possess the virus.
The symptoms of necrosis virus disease are also observed in weed plant Xanthium.
As the disease is caused by virus, control measures are not possible after the infection.
As prevention is the strategy to manage the disease, the stress should be on controlling the thrips which are carriers of the virus. Farmers may adopt the following measures to control the pest:
Planting 4-6 lines of tall growing border crops like bajra, sorghum or maize all around the sunflower.
Protection from thrips
Treating the seeds with insecticide Imidacloprid 70 WS at 5 g/kg of seeds before sowing which will give protection against thrips for 30 days.
Spraying of insecticide Imidacloprid 17.8 SL at 0.25 ml/litre or oxydematon methyle at 1.5 ml/litre after 30 days of sowing.
Planting in the month of June and August may be avoided.
Instead a short duration pulse crop may be planted during this season.
Sunflower sown during September records less disease and yields more. The fields should be kept free from weeds.
Raghavendra K. Mehta
University of Agricultural Sciences
Dharwad, Karnataka.
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