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Diseases of neem, senna and pyrethrum.pdf
- 1. Siddu Lakshmi Prasanna CourseNo.: PATH 2.7.1. Course Title: Diseases of Fruit, Plantation, Medicinal and Aromatic crops By Dr. Siddu Lakshmi Prasanna Ph. D (Agri.) Dept. of Plant Pathology
- 2. Neem 1)Phoma twig blight:Phomopsis azadiractae 2)Powdery mildew: Oidium azadiractae (Erysiphae) 3)Root rot: Ganoderma lucidum 4)Leaf web blight: Rhizoctonia solani 5)Leaf spot: Pseudocercospora subsessilis 6)Bacterial wilt: Pseudomonas azadiractae 7)Angular leaf spot: Xanthomonas azadiractae
- 3. Symptoms: • The diseaseis more pronounced during August to December, though can be observed throughout year. • Appearance of symptoms starts with the on-set of rainy season and becomes progressively severe in later part of the rainy season and early winter season. • The terminal branches are mainly affected. The disease results in the progressive death of the tree, year after year. • Twig blight is the major symptom. Disease also results in inflorescence blight and fruit rot resulting in almost 100% fruit yield loss. Phoma twig blight: Phomopsis azadiractae
- 4. Pathogen: • Disease spreadsthrough conidia that are disseminated by rain droplets and insects. • The pathogen is also seed-borne.
- 5. Senna 1.Alternaria Leaf spot: Alternaria alternata 2.Damping off : Rhizoctonia bataticola
- 6. Leaf spot isthe most serious among the diseases causing lot of damage to the senna crop. The infested leaves drop off prematurely and affect the yield considerably. SYMPTOMS • The disease becomes visible first as minute pale yellow spots on the leaf blade and its margins. • As the spot grow in size they become circular and irregular in shape with their coalesce and turn dark brown to black in colour. • The lesions vary from a minute spot to about 8 mm diameter in size. Alternaria Leaf spot : Alternaria alternata
- 7. • Concentric ringsare formed on the leaves. • Spot size increases and covers the entire leaf resulting in blightening of leaves. • With the advancement of the disease, leaf tips and margins die and the necrotic tissues increase in size. • The disease is known to adversely affect the sennosides content in leaves and it is inversely proportional to the disease intensity. • Loss of sennosides in severely affected leaves was over 60% as compared to that in disease-free leaves. • In advanced stages the pods are also affected with brownish black spots.
- 8. Etiology • Septate mycelium,either the conidia or conidiophores are coloured. Conidia have both longitudinal as well as transverse septa (Dictyosporae) Epidemiology • Nutritionally poor soil, • Temp 28-35 ° C and RH 85-90% are favourable. • Susceptible host. Disease Cycle: • Primary source of inoculum: Dormant mycelia or Survives in crop residue or through use of diseased seed. • Secondary source of inoculum: Wind borne/Rain spread conidia.
- 9. Management • Collect anddestroy the infected plant parts • Use disease free seed. • Amend the nutritional status of the soil • Reduce plant population • Spray mancozeb or Zineb or Rovral 0.25% at 15 day interval.
- 10. Damping off: Rhizoctoniabataticola SYMPTOMS • In the North-Western India, senna is affected by the damping-off disease at seedling stage. • Initially water soaked lesions appear on the collar region of the plant. • After brown discoloration follows the epidermal layer collapse. Seedlings topple down. • The damping-off in seedlings is the most devastating disease.
- 11. Etiology • Septate mycelia,sub - epidermal haustoria • Asexual spores are absent and mycelial strands cause infection • Vegetative structure: Sclerotial bodies Epidemiology • Warm weather, soil temp 28-32° C with optimum moisture and neutral pH Primary Source of Inoculum :Sclerotial bodies Secondery Source of inoculum: Soil borne mycelial strands
- 12. Disease cycle • Itis a Deuteromycetes fungus that produces sclerotial bodies which are sesamum seed like vegetative resting structures. • Under congenial conditions these sclerotial bodies germinate, penetrate inside the host and causes disease. • The mycelial strands inside the affected host again germinate and cause infection and disease cycle continues.
- 13. Management: • Destruction ofdiseased debris. • Deep ploughing during summer. • Crop rotation with non- host crops • Soil sterilization • Biological control with T. viride • Seed treatment with thiram or captafol at 2.5 g/kg of seed gave good protection. • Soil drenching with Carbendazim (0.1%) or Mancozeb (0.2%). • Seed treatment with Thiram+Bavistin @1.5 g each /kg seed.
- 14.
- 15. 1. Damping off: Pythium spp., Phytophthora spp. 2. Wilt : Rhizoctonia solani 3. Rust : Puccinia horiana 4. Leaf blotch : Septoria chrysanthemella 5. Grey mold : Botrytis cinerea 6. Fusarium wilt : Fusarium oxysporum f. sp. solani 7. Root rot : Sclerotinia minor 8. Ray blight : Phoma ligulicola var. inoxydablis
- 16. Symptoms: ➢ Pre emergencedamping off. ➢ Water soaked lesions on collar region, leading to rottening and damping off. ➢ Stem size reduction. ➢ Toppling over of seedlings & death. ➢ Post emergence damping off and rotting of roots of stem cuttings. ➢ Plants will die suddenly Damping off : Pythium spp. and Phytophthora spp.
- 18. Disease Cycle: PSI: Oospores/Chlamydosporesin soil. SSI: Sporangia spread by rain splashes. Management: ➢ Pre-plant sterilization of soil medium. ➢ Better drainage and avoid excessive shade. ➢ Soil drench with Thiram/Captan @2.5 gm/lit or Copperoxychloride @3g/lit.
- 19. Symptoms • Infection appearsinitially in the form of dark brown, necrotic lesions on the roots and basal parts of the plant, which later turn into root rot and wilt symptoms, leading to premature death and desiccation of infected plants. • Stolons exhibit pinkish brown lesions initially. Which gradually turns into dark brown lesions. • Later turns from dark brown to black patches that increase in size resulting in soft decay. Root rot and wilt - Rhizoctonia solani
- 21. Management • Affected debrisdestruction • Summer ploughing • Crop rotation • Soil sterilization • Biological agent Trichoderma spp. • Carbendizim 0.1% or Mancozeb 0.25% as soil drenching. • Seedlings should be grown in disease-free soil. • Raised nursery beds should be prepared. • Nursery beds should be drenched with 0.15% benomyl or 0.1% zineb.
- 22. Symptoms • Infected plantscan be symptomless, especially during hot and dry conditions. Symptoms usually appear during cooler, wet weather and it may take up to 8 weeks before infected plants show symptoms during periods of hot weather. • Symptoms appear as small white to yellow spots up to 4 mm wide on the upper surface of the leaf. • These spots may be slightly dimpled and become brown as the disease progresses. Pustules form on the underside of the leaf just beneath the small spots observed on the upper surface of the leaf. Rust : Puccinia horiana
- 23. • These pustulesoriginally appear as buff to pink-coloured. As they age, they become white. • Pustules are most common on young leaves and flower bracts but can be found on any part of the foliage including flowers. A. Early symptoms of yellow white, dimpled spots on the upper leaf surface B. Young pink brown pustules on under surface of the leaves
- 24. A. Young pinkbrown pustules on under surface of the leaves B. Mature white pustules on under surface of the leaf
- 25. Pathogen- Microcyclic andautoceious rust, Uredial stage is absent Management: ➢ Use of healthy suckers for planting. ➢ Picking off lower leaves at planting and replanting. ➢ Spraying with Wettable Sulphur 0.2% or Zineb 0.2% or mancozeb 0.25 % or Hexaconazole 0.1 % at 10-15 days gap. ➢ Crop rotation with non host crop.
- 26. Symptoms: ➢ Initially smallcircular/irregular brownish black spots on leaves with an yellow halo. ➢ Large patches are formed due to merging of such spots covering major portion of leaf. ➢ Leaves remain small and curl. ➢ Leaves shed or hang on the stem for some time ➢ Severe in rainy weather. Leaf blotch : Septoria chrysanthemella
- 28. Disease Cycle: PSI: Survivesin crop residue or through use of disease suckers. SSI: Wind borne/Rain spread conidia. Etiology • Mycelium is septate inter and intrecellular haustoria, • Sexual spores are Ascospores borne in pseudothecium. • Primary source of inoculum is Ascospores (pseudothecium) • Secondary source of inoculums is pycnidiospores • Mode of spread is infected debris in the soil and rain splash.
- 29. Management: ➢ Adoption ofsanitary measures. ➢ Controlled irrigation. ➢ Spray Carbendazim/Benomyl 0.1% or Mancozeb 0.2% or COC 0.3% at fortnightly intervals.
- 30. Symptoms: ➢ Leaf symptomsstart from margins and spread to center and base a semicircular band. ➢ Infected stems appear bleached and often are associated with the presence of cottony mycelium and sclerotia. ➢ Stem girdling, death of upper plants portions ➢ On flowers, infection starts as brown water soaked spots on lower petals and flowers covered with greyish brown powdery mass of spores. ➢ Flower buds do not open. Sterile buds Grey mold : Botrytis cinerea
- 32. Disease Cycle: PSI: Haswide host range. Also produces sclerotia. SSI: Wind/rain spread conidia or contact between healthy and diseased. Management: ➢ Adoption of proper spacing. ➢ Spray of Captan 0.2% or Blitox 0.3% as and when necessary.