Brown leaf spot (Bipolaris oryzae)
This disease was previously called Helminthosporium leaf spot. Most conspicuous symptoms of the disease occur on leaves and glumes of maturing plants. Symptoms also appear on young seedlings and the panicle branches in older plants. Brown leaf spot is a seed-borne disease. Leaf spots may be evident shortly after seedling emergence and continue to develop until maturity.
Leaf spots vary in size and are circular to oval in shape. The smaller spots are dark brown to reddish brown, and the larger spots have a dark-brown margin and reddish brown to grey centres. Damage from brown spot is particularly noticeable when the crop is produced in nutritionally deficient or otherwise unfavourable soil conditions. Significant development of brown spot is often indicative of a soil fertility problem.
- Plant resistant varieties.
- Use certified high quality disease-free seeds.
- Ensure balanced fertilisation.
- Practise crop rotation.