Alternaria leaf spot:
Symptoms:
- Seed become small and shriveled. Dark, irregular, spreading sunken areas occur on the seed.
- Appearance of brown, necrotic spots with concentric rings on foliage, which coalesce and form large necrotic areas.
- Infected leaves later in the season dry out and drop prematurely.
Management:
- Use healthy/certified seeds
- Destroy crop residues from fields.
- Seed treatment with thiram + carbendazium (2:1) @ 3g/kg seed.
- Use Mancozeb or copper fungicide at 2.5g/l or carbendazim 1 g/lit.
Cercospora leaf blight, leaf spot and Purple seed stain:
Symptoms:
- Infected leaves appear leathery, dark, reddish purple.
- Severe infection cause rapid chlorosis and necrosis of leaf tissues, resulting in defoliation.
- Lesions on petioles and stems are slightly sunken, reddish purple; severe cause defoliation.
- Later, blighting of young, upper leaves over large areas, even entire fields occur.
Management:
- Use healthy/certified seeds.
- Previous crop debris should be removed.
- Seed treatment with Thiram + Carbendazium (2:1) @ 3g/kg seed.
- Use Mancozeb or copper oxychloride at 2.5g/l or Carbendazim 1 g/lit.
Stem Fly:
Symptoms:
- The eggs are laid on leaves.
- After hatching from the egg yellowish maggots bore the nearest vein of the leaf.
- The maggot then reach the stem through petiole and bore down the stem.
- If the infected stem is opened by splitting, distinct zig zag reddish tunnel can be seen with maggot or pupae inside it.
- The maggots feed on cortical layers of the stem, may extend to tap root, killing of the plant.
Management:
- Deep summer ploughing.
- Avoid pre monsoon sowing.
- Use optimum seed rate and plant spacing.
- Proper crop rotation with dissimilar crops should be followed.
- Remove and destroy the damaged plant parts.
- Soil application of phorate 10 G @ 10 kg/ha or carbofuran 3 G @ 30 kg/ha at the time of sowing will prevent early infestation by stem fly.
- One or two sprays of 0.03% dimethoate 30 EC or 0.05% quinalphos 25 EC can stop the damage.
Girdle beetle:
Symptoms:
- Girdling of stems and petioles
- The inside of the stem is eaten by the larvae and a tunnel is formed inside the stem.
- The leaves of plant of infected portion are unable to get the nutrient and are dried up.
- In later stages the plant is cut at about 15 to 25 cm above the ground.
Management:
- Deep summer ploughing
- Planting time on the onset of monsoon
- Optimum seed rate (70-100 kg/ha) should be used
- Intercropping with maize or sorghum should be avoided
- Crop rotation should be followed
- Avoid excess nitrogenous fertilizers.
- Collect and destroy infested plant parts and egg masses.
- Remove the infested plant parts at least once in 10 days and bury them in compost pit to monitor and reduce the populations of girdle beetle
- Apply phorate 10 G @ 10 kg/ha or carbofuran 3 G @ 30 kg/ha at the time of sowing.
- One or two sprays of 0.03% dimethoate 30 EC or 0.05% quinalphos 25 EC or 0.05% methyl demeton 25 EC or 0.04% can check further damage.
- Spray quinalphos 25 EC triazophos 40 EC @ 2 ml/lit. at the crop age of 30-35 days and repeal after 15-20 days (1000 l spray/ha)
Soybean Aphid or Jassids:
Symptoms:
- They suck the plant sap from the stem, leaves and pods which cause reduction in yield.
- The infested leaves are wilted or curled.
- Plant stunting, reduced pod and seed counts, puckering and yellowing of leaves.
Management:
- Dusting of cow dung ash and spraying of clay suspension as asphyxiants (in small area and low incidence of sucking insects)
- Spray 0.05 % quinalphos 25 EC, oxydemeton methyl 25 EC, or dimethoate 30 EC @ 2ml /lit at the crop age of 35-40 days and repeat after 15 days if needed
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