BROWN SPOT DISEASE
Causal organism: Helminthosporium Oryzae / Drechslera Oryzae
Symptoms:
· Brown spot disease symptoms in rice occurs on nursery as well as on main crop.
· Round or oval brown colored spots are formed on the leaves.
· Spots measures 0.5-2.0mm in breath and resemble sesame seeds.
· Spots are eye shaped with conspicuous dark brown at center and light margin.
· Later on, the spots enlarge and emerged to from patches on leaves.
· Several leaves show blight symptoms.
· Brown colored spots also develop on grain.
· Panicle neck show brown discoloration.
Favourable condition:
· Temperature= 25-30 degree.
· Relative humidity= above 80%
· Excess of nitrogen aggravates the disease severity.
Disease cycle:
Perennation:
· through seeds and plant debris.
Primary infection:
· from infected seeds and plant debris.
Secondary infection:
· through conidia spread from plant to plant with the help of wind, water and rain splashes.
Diagram of brown spot disease cycle:
Management:
Culture method
· Remove plant debris and weed host before field preparation.
· Grow resistant varieties: Co44 and Bhavani etc.
· use disease free seeds.
· Proper sanitation application applies in the field. E.g.: soil solarization.
· Proper spacing maintain row to row and plant to plant.
· Remove infarcted part of the plant.
· Apply good weed management practices.
· Apply good irrigation application in the filed area.
Chemical method
· Use of sloe release nitrogenous fertilizers is advisable.
· Treat the seeds with Thiram or Captan at 4g/kg. Spray the nursery with Edifenphos 40ml or Mancozeb 80g for 20% nursery.
· Spray the crop in the main field with Edifenphos 500ml or Mancozeb 2kg/ha when grade reaches3. If needed repeat after 15 days.
