Crucifers diseases and spread management.pptx

Pathology

1. Diseases of crucifers Symptoms, Pathogen, Favourable Conditions, Mode of Spread and Survival, Management By V.VIJISHREE 2021004129

2. 1. Club root of cabbage/ Finger and toe disease: Plasmodiophora brassicae Symptoms : • Leaves pale green to yellowish • Plants stunted fail to produce marketable heads • Small or large spindle like, spherical, knobby or club shaped swellings on the roots and root lets • Diseased plants later die

3. Pathogen It is a Protozoa. Plasmodium (naked protoplasm) produces primaryand secondary zoospores. zoospores are biflagellate. Sexual spores are resting spores

4. Mode of spread Primary : Resting spores .Through farming implements, Surface flood water and from infected seedlings. Manure from cattle fed on diseased root crops. Secondary : Zoospores

5. Favorable conditions Clubroot is a disease that prefers warmer temperatures and moist conditions Ideal conditions for the proliferation of this disease would be a soil temperature between 20–24 °C pH less than 6

6. Management 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%.

7. DAMPING OFF/WIRE STEM OF CABBAGE Thanetophorus ( Rhizoctonia ) solani Symptoms : Serious in nursery of cabbage Causes wire stem in seedlings Tissues water soaked and toppling of seedlings Damping off in seedling, wire stem in seedlings (plants blend or twisted withoutbreaking in cabbage) Bottom rot, head rot and root rot in older plants

8. Pathogen: Septate mycelium. Sclerotia are irregular brown to black. Produces terminal and intercalary chalamydospores . Basidia with basidiospores are produced Perfect stage: Thanatephorus cucumeris

9. Favorable condition: cool, cloudy weather, high humidity, wet and compact soil and overcrowding. Mode of spread: Primary: Sclerotia and Basidiospores; Secondary: Water borne sclerotia and chlamydospores

10. Management : Adopt raised seedbed method. Treat the seeds with Trichoderma asperellum 4g/kg Avoid excessive irrigation to reduce humidity around the plants Discard the diseased seedlings before transplanting Soil drench with carbendazim 0.1 % or copper oxychloride 0.25%

11. 3. BLACK LEG OF CABBAGE: Phoma lingam Symptoms: Fungus attacks the crop at seedling or any stage of crop growth Oral, depressed, height brown canker appear near the base of stem Canker enlarges and girdles the stem
Attacked roots show dark brown cankers Elliptical lesions appear on seed stalk and pods

12. Pathogen: Septate mycelium, produces pycnidia . Ascocarps bear asci with ascospores Favourale condition: continued drizzling and wet weather

13. Mode of spread: Primary: Ascospores ; Secondary: Water borne conidia Management: Follow deep summer ploughing to incorporate crop debris promptly after harvest to hasten decay Practice four year rotation in seedbeds and fields

14. Use certified/disease free seeds Treat seeds with hot water as it spreads mainly through seeds Dress the seeds with imidacloprid+metalaxyl+carbendazim based products Rouge out and destroy diseased plants from seedbeds Improve soil drainage and air circulation. Avoid working in the fields when wet

15. 4. CABBAGE YELLOWS/FUSARIUM WILT OF CABBAGE: Fusarium oxysporum f.sp . conglutinans S y mptoms : Plants show uniform yellowing Stem and leaves curl laterally Later leaves turn brown, brittle and die Browning of vascular system seen

16. Pathogen : Produces microconidia , macroconidia , and chlamydospores Favourable condition: soil moisture, acidic pH, root wounds and the temperature about 27 °C Mode of spread: Primary : Chlamydospores Secondary : Water borne conidia

17. Management Use only certified, disease free seeds/transplants Growing seedlings in seed bed disinfested by stream or soil fumigant Grow resistant varieties. Early sowing of cabbage Follow crop rotation with crops like lettuce, chilli , peas, tomato, sweet potato or cotton Remove and destroy infected plant debris.

18. 5. WHITE BLISTERS OR RUST OF RADISH: Albugo candida Host : Cabbage, mustard, radish, turnip Two types of infection: Local systemic

19. Symptoms: • Local infection: isolated pustules or sori develop in leaves and stems. Pustules merge to form larger patches. Host epidermis rupture after maturity of pustules • Systemic infection: When young stems and flowering parts are infected it becomes systemic. Stimulates hypertrophy and hyperplasia • Results in enlarged and variously distorted organ mostly flower parts sepals become enlarged to several times than the normal sepals. Petals enlarge and become green pistils and anthers are distorted. • Seed development is arrested

20. Pathogen Pathogen produces sporangia. Sporangia are spherical / hyaline in nature contains 4-8 zoospores Sexual spore is tuberculate oospore

21. Favourable condition: Moist cool weather and a thin film of water on the leaves Mode of spread: Primary : Oospore Secondary : Sporangia and Zoospores

22. Management Remove and destroy infected plant debris Treat the seeds in hot water at 52 ° C f o r 20 min or metalaxly 4-6g/kg Remove cruciferous weeds in the filed Spray Bordeaux mixtre 1.0% or mancozeb or metalaxyl+mancozeb0.2%

23. 6. DOWNY MILDEW: Peronospora parasitica Symptoms: • It affects seedlings and mature plants. • On seedlings: The entire plant becomes covered in a whitish coating of the pathogen and dies rapidly • On larger plants: Yellowish patches of discolouration on the upper surfaces of leaves, often angular and limited by veins. On the corresponding lower surface is a fuzzy whitish outgrowth of the pathogen. Eventually, the affected tissues die, shrivel and may drop out

24. • On cauliflower curds and radishes : Leaf damage may be accompanied by internal browning of the cauliflower curds and radish flesh. • These infections in turn release spores and spread to other brassicas by wind and rain .

25. Pathogen The sporangiophores are dichotomously branched at acute angles and taper into gracefully curved pointed tips on which sporangia are borne.

26. Favourable condition Cool moist conditions, high humidity, fog, drizziling rains and heavy dew. Optimum temperature for the conidia is 8 to 10°C For conidial germination 8 to 12°C and for host penetration 16°C, rapid development 15 to 20°C. Mode of spread: Primary : Oospore Secondary : Sporangia and Zoospores

27. Management • Follow crop rotation with non cruciferous crops • Grow tolerant varieties. Treat seeds with metalaxyl 6g/kg • Remove cruciferous weeds in the filed • Spray metalaxyl+mancozeb or metalaxyl 0.4% or mancozeb0.2%

28. 7. BLACK ROT: Xanthomonas campestris pv . campestris Symptoms: • Infected young plants killed. Plants stunted Cotyledons turn yellow to black, hang down and drop off prematurely • Leaves yellow with blackened veins and vein lets . Become necrotic and brittle V shaped chlorotic to yellow lesions develop from the leaf margin D isease spreads onto the roots Vascular bundles become black and the fleshy tissue break down • Cabbage heads and cauliflower curds are infected and discoloured

29. Pathogen : Gram negative, rod shaped bacterium with single polar flagellum Mode of spread: Wind driven rain splashes carry bacteria from infected to healthy leaves, Twigs and fruits Favourable condition Optimum temperature 26.5 to 30°C and frequent rain

30. Management Grow tolerant varieties. Follow atleast four year rotation with cruciferous crops Treat the seeds in hot water at 50 C for 30 min or with streptocycline 100 ppm for 30 min kills bothinternally and externally seed borne bacterium Grow seedlings on raised beds in non infested area or frequently change th nursery site and get disease free seedlings Avoid low, wet soils with poor soil drainage. Keep the field fallow for 2 years Raise intercrops like mungbean or urdbean as mulches to reduce the spread of pathogen by rain splashes Remove and destroy diseased plants and weed hosts
Drench the nursery soil with formalin 0.5% ro apply bleaching powder 12.5 kg/ha
Spray copper oxychloride 2.5 g/ lt + streptocycline at 100 ppm or Kasugamycin 0.2%

31. 8. CAULIFLOWER MOSAIC: Cauliflower mosaic virus, Double strand DNA virus Symptoms: • Leaves are mottled with a pattern of light and dark green • Plants are stunted, central leaves smaller • Mild infection leads to production of a small and poor quality heads • Infected plants die

32. Transmission : Aphids - Brevicoryne brassicae Other disease • Whiptail disease: Caused by molybdenum deficiency

33. Thank you