BROWN SPOT OF PADDY

DISEASE OF FIELD CROPS

1. Brown spot of paddy A.Nitha Reddy 111718012002 DAG-A

2. Brown spot : PATHOGEN: Bipolaris oryzae (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 symptoms of 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 brown to 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. DISEASE CYCLE: Externally seed borne disease. Primary infection is through seed. Disseminated by air currents. Collateral host : Digitaria sanguinalis , Echinocloa colonum .

6. FAVOURABLE CONDITION : Temperature ranging from 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 of disease 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 [email protected]% after flowering and milky stage.