| Stemphylium Leaf Blight |
Small, light-brown lesions that enlarge and turn dark brown or black, leading to extensive leaf blighting.
Control: Spraying Mancozeb (0.25%) along with Monocrotophos (0.05%) with sticker triton on appearance of disease at fortnightly interval controls the disease. |
| Downey Mildew |
Pale green or yellow spots on leaves covered with a downy, violet-white fungal growth during humid weather.
Control:Spray Mancozeb or Metalaxyl. Destroy infected plant debris and ensure adequate plant spacing to allow air circulation. |
| Fusarium basal rot |
Yellowing and wilting of leaves; roots rot and turn pink or brown; bulb base decays.
Control: Seed treatment with Thiram (2 g/kg of seed) and soil application of Carbendazim, Thiophanate Methyl (Topsin-M) or Benomyl @ 0.1% is effective in the controlling the disease. |
| Damping-off |
The pathogen attacks the collar region of seedlings on the surface of soil. The collar portion rots and ultimately the seedlings collapse and die.
Control: The seed should be treated with Thiram @ 2g/kg of seed before sowing. |
| Purple blotch |
Small, sunken, watery spots on leaves that turn purplish-brown. Leaves eventually break and wither.
Control:Spraying Mancozeb (0.25%) or Chlorothalonil (0.2%) or Iprodione (0.25%) after one month from transplanting at fortnightly interval reduces the disease incidence. |
| Rust |
Small white flecks on leaves and stems which develop into circular or elongated orange pustules; severe infestations can cause leaves to yellow and die
Control: Spray Tebuconazole @ 1 ml / ltr. Or Mancozeb @ 2 gm / ltr |
| Bacterial Brown Rot |
It is very serious disease of onions in storage. The infection occurs through the wounds. The rot begins at the neck of the bulbs which later gives foul smell through the neck when squeezed.
Control: Proper curing and rapid drying of the bulbs after harvesting is essential for controlling the disease. Affected bulbs should be discarded before storage. If rains occur during maturity, spraying of Streptocycline (0.02%) is recommended. |
| Smut |
Dark, thickened lareas on cotyledons (seed leaves) which may become large and cause leaves to bend downwards; raised blisters may be present on the base of scales in older plants; lesion mature and become covered in black powdery fungal masses; plant growth stunted; death of plant occurs within 3-4 weeks
Control: Treating the seeds with Captan or Thiram (2.5g/kg of seed) before sowing controls the 2 disease. Seed bed treatment with Methyl Bromide (1 kg/25 m .) is effective in controlling the disease. |
| White rot |
Extremely persistent soil-borne disease forming white, fluffy mycelium on roots/bulbs.
Control: Seed treatment with Thiram (4 g/kg of seed) and drenching of soil with Mancozeb (0.25%) are effective in controlling the disease. Application of bio-control agents like Trichoderma viride to the soil reduces the disease inoculum. |
| Leaf streak and bulb rot |
Water-soaked, dark green oval lesions or streaks on leaves; tipburn of leaves; dark spots on wrapper scales of bulbs; reddish-brown discoloration of inner scales; rot developing in ring-like pattern
Control: foliar sprays of mancozeb (80% WP) or chlorothalonil (75% WP) |
| Onion yellow dwarf |
Yellow streaks on bases of of first leaves; all leaves which emerge after infection have yellow streak or are completely yellow; leaves may be flattened or crinkled; bulbs are undersized; flower stalks yellow and twisted; flower clusters small and seed is of poor quality
Control: Spraying of Malathion (0.1%) or Metasystox (0.1%) to control the vectors checks further spread of the disease. |
| Black Mold |
Post-harvest black discoloration at neck; lesions on outer scales; black streaks under outer dry scales; entire surface of bulb turning black and shriveling
Control: The crops should be sprayed with Carbendazim (0.2%) 10-15 days before harvesting. |
