Major Cabbage diseases are given below:-
1.Black leg: Phoma lingam
- It is caused by Phoma lingam and occurs in most regions, especially in areas with rainfall during the growing period.
- The fungus is carried by the seed and hence it may occur from the early stage.
- The stem of the affected plant when split vertically, shows severe black discoloration of sap stream. Whole root system decays from the bottom upwards.
- Frequently, the affected plants fall over in the field.
- Seed infection can be prevented by spraying the seed plants with copper oxychloride or with an organic mercuric compound.
- Seed treatment with Captan or Thiram 4g/kg of seed, followed by seed treatment with Trichoderma viride 4g/kg.
- Pusa Drumhead, a cabbage cultivar has been reported to be tolerant under field condition.
2.Downy mildew: Peronospora parasitica
- It may attack young plants and also at the seed production stage as being commonly observed in northern India in recent years when high humidity prevails during seed production stage.
- The fungus when attacks the young seedlings, discoloration occurs and in severe cases, the whole plant perishes.
- Purplish leaf spots or yellow brown spots on the upper surface of the leaf appear while fluffy downy fungus growth is found on the lower surface.
- Seed treatment with Metalaxyl (Apron 6g/kg of seed )
- Foliar spraying with Metalaxyl (Ridomil) 0.4%.
3.Root rot: Rhizoctonia solani
- Young plants show soft, water soaked lesion on the stem near soil level, the cotyledons wither and the plant eventually falls over and perishes.
- When infection occurs at a later stage of growth, the lower part shows discoloration over a length of several centimetres, becomes hard and woody, and thinner than usual as the cortical tissue dies and this phenomenon is known as wire stem.
- Nursery beds: Soil drenching with Methyl bromide @ 1 kg/10 m 2 and covered with polythene sheet.
- Seed treatment with Captan/Thiram 4g/kg, followed by seed treatment with Trichoderma viride 4g/kg.
4.Black spot: Alternaria sp.
- In older plants, leaves, petioles, and stems small, brown to black circular to slightly elongated spots appear. Sometimes the spots join together.
- It causes damage to cabbage heads and cauliflower curds after maturity and during seed production stage.
- First foliar spraying with Tridemorph 0.1% followed by spraying with Mancozeb 0.25% a month interval.
5.Clubroot: Plasmodiophora brassicae
- Stunting and yellowing of plants
- Leaves become yellowish and wilt on hot days.
- Clubs like swelling of root and root lets
- Club root is particularly prevalent in soils with a pH below 7, whereas it has been observed that the disease is often less serious on heavy soils and on soils containing little organic matter.
- Soil fumigation with Methly bromide 1kg/10m 2 followed by covering with plastic film.
- Seed treatment with Captan/Thiram 4g/kg, followed by T.viride 4g/kg.
- Application of lime 2.5 t/ha.
- Soil drenching with Copper oxychloride 0.25%.
6.Powdery mildew: Erysiphe polygoni
- Initially, white tufts of mould arise on the upper surface of the leaves and later run together and the entire leaf becomes covered with greyish white mycelium.
- Spary inorganic sulphur 0.25% or Dinocap 0.05%.
7.Damping off: Pythium debaryanum
- Black and reddish brown lesion on the collar region. Finally, infected seedling is toppled on the ground surface.
- The disease is promoted by high humidity and high temperature and the damage in the seed bed, in general, is considerable.
- Seed treatment with Captan/Thiram 4g/kg, followed by seed treatment with T.viride 4g/kg.
8.Black rot: Xanthomonas campestris pv. campestris
- The infection of the foliage results in yellow ‘V’ shaped spots arising along the margin which extends in the direction of the midrib.
- These spots are associated with a typical black discoloration of the veins.
- The infection extends through the xylem to the stalk and the vascular bundles turn black. In severe infection, the whole leaf shows discoloration and eventually falls off.
- Seed treatment with Aureomycin 1000ppm for 30 min is effective in killing both the internally and externally seed-borne pathogen.
- Drenching the nursery soil with formaldehyde 0.5% helps in checking the disease.
- Application of bleaching powder at 10.0 to 12.5 kg/ha controls the disease.
- TamilNadu Agritech Portal