Tiêu đề Pathology Part-3.pdf ✅

www.iaritoppers.in Whatsapp : +91-9694095242 Page | 1 Plant Pathology 4 th Edition 2023-24
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 2 Diseases of Rice Disease Causal organism 1. Blast Pyricularia oryzae 2. Sheath Blight Rhizoctonia solani 3. Brown spot Heminthosporium oryzae 4. Foot rot or bakane disease Fusarium moniliforme 5. Bacterial leaf blight Xanthomonas oryzae pv. Oryzae 6. False smut Ustilaginoidea virens 7. Udbatta disease Ephelis oryzae 8. Bunt or Kernel Smut or black smut Tilletia barclayana 1. Blast - Pyricularia oryzae:  Most severe disease of rice, also known as rich men’s disease. Symptoms:  Leaf Blast, Nodal Blast & Neck Blast are the major symptoms.  On the leaves, the lesions appear as small bluish green flecks, which enlarge under moist weather to form the characteristic spindle shaped spots with grey centre and dark brown margin (Leaf blast).  Severely infected nursery and field appear as burnt.  Infected pedicels result in non-production of seeds (blanking). 2. Brown leaf Spot - Helminthosporium oryzae: Symptoms:  This disease is responsible for The Great Bengal Famine in 1943.  The fungus attacks the crop from seedling to milky stage in main field.  Symptoms appear as minute circular to oval spots on the coleoptile, leaf blade, leaf sheath, and glume, being most prominent on the leaf blade and glumes.  This disease is severe on potash deficient soils.
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 3 Favourable Conditions:  Temperature of 25-30 ̊C with relative humidity above 80 per cent are highly favourable.  Excess of nitrogen aggravates the disease severity. 3. Foot rot or Bakanae disease - Fusarium moniliforme: Symptoms:  Infected seedlings in nursery are lean and lanky, much taller and die after some time. In the main field, the affected plants have tall lanky tillers.  The plants are killed before earhead formation or they produce only sterile spikelets. When the culm is split open white mycelial growth can be seen.  This disease is also known as 'foolish seedling disease'. Management:  The fungus is externally seed-borne.  Treat the seeds with Thiram or Captan or Carbendazim at 2 g/kg. 4. Bacterial leaf blight - Xanthomonas oryzae pv. oryzae Symptoms:  The disease is usually noticed at the time of heading but it can occur earlier also. Seedlings in the nursery show circular, yellow spots in the margin that enlarge, coalesce leading to drying of foliage.  “Kresek” symptom is seen in seedlings, 1-2 weeks after transplanting. The bacteria enter through the cut wounds in the leaf tips, become systemic and cause death of entire seedling.  'Blighting starts from tip of leaves to the base'. 5. False smut - Ustilaginoidea virens Symptoms:  The fungus transforms individual ovaries / grains into greenish spore balls of velvetty appearance. Only a few spikelets in a panicle are affected.
www.iaritoppers.in Whatsapp : +91-9694095242 Page | 4 Favorable conditions:  Rainfall and cloudy weather during flowering and maturity 6. Udbatta disease - Ephelis oryzae Symptoms:  The entire ear head is converted into a straight compact cylindrical black spike like structure since the infected panicle is matted together by the fungal mycelium. Management:  The pathogen is internally seed borne.  Hot water seed treatment at 45 ̊C for 10 min. effectively controls the disease. 7. Khaira Disease:  Due to Zinc deficiency.  Chlorotic/yellow patches at leaf base on both sides of midrib; restricted root growth and usually main roots turn brown.  Apply ZnSO4 @ 25 kg/ha. at the time of sowing. Viral Diseases Disease Symptoms/ Remark Rice Tungro Disease (RTD) - Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV)  Infection occurs both in the nursery and main field.  Plants are markedly stunted. Leaves show yellow to orange discoloration and interveinal chlorosis.  Panicles not formed in very early infection, if formed, remain small with few, deformed and chaffy grains.  Transmission mainly by the leaf hopper vector Nephotettix virescens  Disease can be Identified by Iodine test.