Seedling blight/leaf blight/leaf spot: Helminthosporium nodulosum
Symptom:
- The pathogen affects both seedling and the adult plants
- Minute, oval, light brown lesions on the young leaves and become dark brown
- Several such lesions coalesce to form large patches of infection on the leaf blade. The affected blades wither prematurely and the seedlings may be killed.
- Linear oblong and dark brown spots appear on the leaves of grown up plants. The leaves give the blightening appearance.
- Prominent brown to dark brown discoloration in the neck region and followed by weakening of neck tissue that causes it to break and the ears hanging down from the plant
- While nursery infection causes heavy damage due to the seedling blight, neck infection causes heavy chaffiness and severe loss in grain yield.
- It is seed-borne and primary infection is through seed
- Secondary infection through airborne conidia and stubbles.
Identification of pathogen:
- The mycelium is intra and inter-cellular septate and light brown in colour
- Conidia are erect or curved septate and dark brown. They are borne at the tip of conidiophores
- Conidiophores are thick walled cylindrical or obcavate straight or curved and light green in color and 3-10 septate
- The spores germinate either through the stomata or epidermal cells.
- 11 spores may be formed in one conidiophore
Management:
Chemical method:
- Treat the seeds with Captan or Thiram @4g/Kg
- Spray Mancozeb @ 1.25Kg/ha
- Spray 1% Bordeaux mixture or Copper oxychloride or Dithane Z-78 (2g/lit. water).
Source-
- TamilNadu Agritech Portal.
