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BROWN SPOT OF PADDY
Brown spot of paddy is caused by the fungus Bipolaris oryzae. It causes small reddish-brown spots on rice leaves, sheaths, and grains. The fungus spreads through infected seeds and can survive in collateral hosts. It thrives under warm, wet conditions between 25-30°C and 80-100% humidity. Management strategies include using disease-free seeds, resistant varieties, seed treatments, fungicide sprays, and avoiding excess nitrogen fertilization.
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BROWN SPOT OF PADDY
- 1. Brown spot ofpaddy A.Nitha Reddy 111718012002 DAG-A
- 2. Brownspot: PATHOGEN: Bipolarisoryzae (breda de hann) shoemaker ( syn.Helminthosporium oryzae) This disease was considered to be the major factor contributing to the “Great Bengal Famine”in 1942. It is used by USA as biological weapon in JAPAN during WORLD WAR II
- 3. SYMPTOMS: • The symptomsof disease appear on the coleoptile,the leaves,leaf sheath and also the glumes. • Small circular to oval reddish- brown spots with gray center surrounded by a dark to reddish-brown margin. • The fungus may also infect glumes,causing dark brown to black oval spots and may also infect the grain,causing a black discoloration.
- 4. ETIOLOGY: Greyish brownto dark brown septate mycelium. Conidiophore may arise singly or small group. They are striaght or geniculate(curved)-pale to brown. Conidia are curved with a bulge in centre & tappering towards end Olive green to golden brown,6-14 septate. Sexual fruiting body in sexual stage: perithecia with asci
- 5. DISEASECYCLE: • Externally seedborne disease. • Primary infection is through seed. • Disseminated by air currents. • Collateral host : Digitaria sanguinalis,Echinocloa colonum.
- 6. FAVOURABLECONDITION: Temperature rangingfrom 25°c-30°c. Water stress and high humidity(80-100%). Poorly drained or abnormal soils, which are deficient in nutrient elements. Leaves which are wet for 8-24 hrs are prone to infection.
- 7. MANAGEMENT: use ofdisease free seeds. Use of resistant varieties. Avoid excess use of N application Use of silicon fertilizers(eg.calcium silicate slag). Hot water seed treatmemt (54-54°c)for 10-12min. Seed treatment with captan,thiram or carbendazim. Spray Mancozeb@0.2% after flowering and milky stage.