DISEASES OF CASTOR.pptx
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IT COVERS ALL THE MAJOR DISEASES OF CASTOR CROP
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DISEASES OF CASTOR.pptx
- 1. DISEASES OF CASTOR SUJIT KUMAR SETHY (55A-21M/PP) MSc. PLANT PATHOLOGY, COLLEGE OFAGRICULTURE, CENTRALAGRICULTURAL UNIVERSITY, IMPHAL
- 2. Seedling blight Phytophthora parasitica Dead seedling Leaf blight symptom Spot on older leaf
- 3. Symptoms • The disease appears circular, dull green patch on both the surface of the cotyledon leaves. It later spreads and causes rotting. • The infection moves to stem and causes withering and death of seedling. • In mature plants, the infection initially appears on the young leaves and spreads to petiole and stem causing black discoloration and severe defoliation.
- 4. Disease cycle • The pathogen remains in the soil as chlamydospores and oospores which act as primary source of infection. • The fungus also survives on other hosts like potato, tomato, brinjal, sesamum etc. • The secondary spread takes place through wind borne sporangia.
- 5. Favorable Condition • Continuous rainy weather. • Low temperature (20-25˚C). • Low lying and ill drained soils Management • Remove and destroy infected plant residues. • Avoid low-lying and ill drained fields for sowing. • Treat the seeds with thiram or captan at 4g/kg.
- 7. Symptoms • Minute, orange-yellow coloured, raised pustules appear with powdery masses on the lower surface of the leaves and the corresponding areas on the upper surface of the leaves are yellow. • Often the pustules are grouped in concentric rings and coalesce together to for drying of leaves.
- 9. Pathogen • The pathogen produces only uredosori in castor plants and other stages of the life cycle are unknown. • Uredospore are two kinds, one is thick walled and other is thin walled. They are elliptical to round, orange-yellow coloured and finely warty. Disease cycle • The fungus survives in the self sown castor crops in the off season. • The infection spreads through airborne uredospores.
- 10. Management • Rogue out the self-sown castor crops and other weed hosts. • Spray Mancozeb at 2kg/ha or Propioconazole 1l/ha.
- 12. Symptoms • All the aerial parts of plants viz., leaves, stem, inflorescences and capsules are liable to be attacked by the pathogen. • Irregular brown spots with concentric rings form initially on the leaves and covered with fungal growth. When the spots coalesce to form big patches, premature defoliation occurs.
- 13. Pathogen • The pathogen produces erect or slightly curved, light grey to brown conidiophores, which are occasionally in groups. Conidia are produced in long chains. Conidia are obclavate, light olive in colour with 5-16 cells having transverse and longitudinal septa with a beak at the tip. Disease cycle • The pathogen survives on hosts like Jatropha pandurifolia and Bridelia hamiltoniana. • The pathogen is externally and internally seed-borne and causes primary infection. The secondary infection is through air-borne conidia.
- 14. Favourable Conditions • High atmospheric humidity (85-90 %). • Low temperature (16-20˚C) Management • Treat the seeds with captan or thiram at 2g/kg. • Remove the reservoir hosts periodically. • Spray mancozeb at 2kg/ha.
- 15. Symptoms • The disease appears as minute brown specks surrounded by a pale green halo. The spots enlarge to greyish white centre portion with deep brown margin. The spots may be 2-4 mm in diameter. • Infected tissues often drop off leaving shot-hole symptoms. In severe infections, the older leaves may be blighted and withered. Brown leaf spot Cercospora ricinella
- 16. Spots on leaf
- 17. Pathogen • The pathogen hyphae collect beneath the epidermis and form a hymenial layer. Clusters of conidiophores emerge through stomata or epidermis. • They are septate and un branched with deep brown base and light brown tip. The conidia are elongated, colourless, straight or slightly curved, truncate at the base and narrow at the tip with 2-7 septa. Disease cycle • The pathogen remains as dormant mycelium in the plant debris. The disease mainly spreads through wind borne conidia.
- 18. Management • Use of resistant varieties would be the most effective method for combating the disease. • Spraying twice with Mancozeb 2g/lit or Carbendazim 500g/ha at 10-15 day interval reduces the disease incidence. • Treat the seed with thiram or Captan 2gm/kg seed.
- 19. Powdery mildew Leveillula taurica Powdery mass covering entire leaf
- 20. Symptoms • It is characterized by typical mildew growth which is generally confined to the under- surface of the leaf. • When the infection is severe the upper-surface is also covered by the whitish growth of the fungus. Light green patches, corresponding to the diseased areas on the under surface, are visible on the upper side especially when the leaves are held against light.
- 21. Management • When weather is comparatively dry spray twice with wettable Sulphur 2g/lit at 15 days interval, starting from 3 months after sowing. • Spray 1ml hexaconazole or 2ml dinocap / litre of water at fortnight intervals. The variety Jwala is resistant to this disease
- 22. Stem rot Macrophomina phaseolina Bacterial leaf spot Xanthomonas campestris pv. ricinicola
- 23. THANK YOU