Rhizoctonia aerial blight / Web blight:
Symptoms:
- Infected seeds have irregularly shaped tan or light brown sunken lesions.
- Infected leaves appears as water soaked at first instance. They soon take on a greenish brown to reddish brown appearance.
- The infected portion later turns tan brown or black in colour.
- Under high rainfall or high humid conditions, a web like mycelial growth of fungus forms on the leaves.
- Dark brown sclerotia are formed on leaves and petioles.
- The pathogen survives as sclerotia in soil.
- Humid and cool (24-32o C) are favourable weather condition.
Management:
- Avoid dense planting.
- Completely cover plant residue by clean ploughing the field soon
after harvest. - Destroy infected stubble.
- Seed treatment with Thiram + Carbendazium (2:1) @ 3g/kg seed.
- Use Mancozeb or copper fungicide at 2.5gm/l or carbendazim 1 g/lit.
Soybean mosaic: Soybean mosaic virus (SMV) belongs to Poty virus:
Symptoms:
- Infected seeds gets mottled.
- Diseased plants are usually stunted with
distorted (puckered, crinkled, ruffled, stunted, narrow) leaves. - The parts are often stunted.
- Flattened or curved and contain fewer and smaller seed.
- Infected seeds fail to germinate or they produce diseased seedlings.
Management:
- Use healthy/certified seeds.
- Keep the field free from weeds.
- Rogue out infected plants and burn them
- Two foliar sprays of Thiamethoxam 25 WG @ 100 g/ha or Methyl demeton 800 ml/ha at 30 and 45 days after sowing to control the vector
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