PATH 372 Diseases of Horticultural Crops

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Minute yellow spots surrounded by a grayish margin appear on leaflets. Gradually, the centre of the spots turns grayish white with dark brown margins and a yellow halo. Spots coalesce into irregular necrotic patches Complete drying and shrivelling of leaf blade occur giving a blighted or burnt appearance. Large number of globose or ovoid black acervuli appears on the upper surface of affected leaves. Pathogen The fungus produces conidia inside the acervuli. The acervuli are black in colour, cushion shaped, sub-epidermal and break open to expose conidia and black sterile structures, setae. The conidiophores are hyaline, short and simple, bear conidia at the tip singly. The conidia are five celled, the middle three cells are dark coloured, while the end cells are hyaline with 3-5 slender, elongated appendages at the apex of the spore. Disease cycle P.I: Conidia in plant debris S.I: Conidia carried by wind splashed rain water Management Remove older affected leaves and burn Apply heavy disease of potash and improve drainage condition of soil Spray foliage with BM@1% COC or captan @0.2% 1) Bunch rot: Marasmius palmivora DISEASES OF OILPALM Symptoms: Strands of mycelium are seen spreading over the bunch surface in initial stages Mycelium is profuse at the back of the bunch. Mycelium grows over the fruit surface and penetrates the mesocarp and leads to wet rot. Disease spreads rapidly within 2 to 3 months after initiation of monsoon rains. Management: Crown cleaning by removing aborted and dried bunches and inflorescences. Spraying of Carbendazim 0.1% or Bordeaux mixture 1%. 2) Spear rot: Phytoplasma disease Spear rot is an endemic disease in Kerala state. Symptoms: Disease is characterized by chlorosis of young whorl of leaves followed by necrosis. Rotting of spear leaves Reduction is leaf size 78
As the disease advances the trunk gradually tapers. Emergence of inflorescence is arrested leading to loss in productivity. Spread: The disease is infectious, vector borne and lethal. Management: Avoid obtaining seedlings from infected areas to healthy areas. Tetracycline injection 500ppm to trunk reduces the disease. Rougueing of affected plants. Planting of barrier trees to isolate the infection source of other palms. 3) Curvularia leaf spot - Curvularia lunata, C. geniculata Symptoms Small circular translucent yellow spots appear on both the leaf surfaces Lesions turn dark brown with sunken centre and yellowish orange halo A narrow rim of raised tissue with oily appearance is produced around the lesions Persistence of primary lesions within the dead tissue is a diagnostic feature for distinction from other leaf spots. Management Prophylactic spray with Thiram @ 2g/lt 79
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COURSE MATERIAL FOR PATH 372 DISEAS
Page 3 and 4:
Management Preventive measures: Se
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Symptoms: The disease attacks leav
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Tristeza affected trees look chloro
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Symptoms: The disease starts with
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Spraying with Karathane 0.1% or cos
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1. Use of disease free planting mat
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The seedling radicle is negatively
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The finer roots show black streaks
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DISEASES OF PAPAYA Powdery mildew
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4. Leaf curl: Tobacco leaf curl vir
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Management Removal and destruction
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Disease cycle P.I: Through disease
Page 27 and 28: 6) Banana Mosaic / Infectious chlor
Page 29 and 30: Management Spray carbendazim@0.1% o
Page 31 and 32: Cool dry weather Maximum temperatu
Page 33 and 34: 3. Anthracnose / Birds eye disease:
Page 35 and 36: 6. Rust: Phakopsora vitis GLR is co
Page 37 and 38: • Fruit set - 0.15% captafol 2) P
Page 39 and 40: Symptoms Small outgrowths on stem
Page 41 and 42: Severely infected leaves defoliate
Page 43 and 44: Tomato Spotted Wilt Virus. The dise
Page 45 and 46: 1) Little leaf - Phytoplasma LECTUR
Page 47 and 48: stage produces perithecia in which
Page 49 and 50: LECTURE 9 DISEASES OF POTATO 1) Lat
Page 51 and 52: Infected auxillary bud or the leaf
Page 53 and 54: Favourable conditions High soil te
Page 55 and 56: Also transmitted by pollen and seed
Page 57 and 58: Disease cycle P.I: Mycelium or con
Page 59 and 60: Management All collateral hosts in
Page 61 and 62: LECTURE 11 DISEASES OF CRUCIFERS 1)
Page 63 and 64: The fungus is seed borne and cause
Page 65 and 66: DISEASES OF CUCURBITS 1) Downy mild
Page 67 and 68: Disease cycle P.I: Collateral host
Page 69 and 70: 1) Purple blotch - Alternaria porri
Page 71 and 72: DISEASES OF BEANS 1) Anthracnose -
Page 73 and 74: Aphis craccivora, Macrosiphum pisi,
Page 75 and 76: Incorporate green manure crops like
Page 77: Provide proper drainage during rain
Page 81 and 82: The centers of the spots eventually
Page 83 and 84: Disease cycle P.I: Infected plant
Page 85 and 86: Black minute pycnidia develop in th
Page 87 and 88: On stems, infected areas are blacke
Page 89 and 90: 1) Blotch - Septoria chrysanthemell
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PATH 372 Diseases of Horticultural Crops

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