The pathogen can survive as sclerotia or mycelium in dry soil for about 20 months but for 5-8 months in moist soil. It infects more than 188 crop species in 32 families. Sclerotia spread through irrigation water.
High relative humidity (96-97 per cent), high temperature (30-32OC), closer planting and heavy doses of nitrogenous fertilizers.
1. Rhizoctonia solani (Sexual stage : Thanetophorus cucumeris)
2. The fungus produces usually long cells of septate mycelium which are hyaline when young, yellowish brown when old.
3. It produces large number of globoses sclerotia, which are initially white, later turn to brown or purplish brown.
1. The fungus affects the crop from tillering to heading stage. Initial symptoms are noticed on leaf sheaths near water level. On the leaf sheath oval or elliptical or irregular greenish grey spots are formed.
2. As the spots enlarge, the centre becomes greyish white with an irregular blackish brown or purple brown border .
3. Lesions o
- Field sanitation: Removal of collateral hosts and infected debris in the field.
- Crop rotation, adjustment of planting time and proper fertilization are suggested.
- Use of slow release nitrogenous fertilizers is advisable.
- Use disease free seeds.
- Resistant variety: Grow disease tolerant varieties like Birsamati, Birsa Vikas Dhan 110, Birsa Vikas Dhan 109, Hazaridhan, Sadabahar, Birsa Dhan 108, Shivam, Virendra, Sugandha and Rajashri showed resistance against brown leaf spot of ri
1. The infected seeds are the most common source of primary infection. The conidia present on infected grain and mycelium in the infected tissue may viable for 2 to 3 years.
2. The fungus may survive in the soil for 28 months at 30OC and 5 months at 35OC. Airborne conidia infect the plants both in nursery and in main field.
3. Maximum flight of conidia take place at a wind velocity of
4.0 - 8.8 hr. Minimum temperature of 27 -28OC, Relative humidity of 90-99% and rainfall of 0.4 -14.4 mm
1. Temperature of 25-30OC with relative humidity above 80 per cent are highly favourable. Excess of nitrogen aggravates the disease incidence.
1. Helminthosporium oryzae (Syn : Drechslera oryzae) (Sexual stage : Cochliobolus miyabeanus).
2. H. oryzae produces greyish-brown to dark brown septate mycelium. Conidiophores may arise singly or in small groups.
3. They are straight, sometime geniculate, pale to brown in colour. Conidia are usually curved with a bulge in the centre and tapering towards the ends occasionally almost straight, pale olive green to golden brown colour and are 6-14 septate.
4. The perfect stage of the fungus
1. The fungus attacks the crop from seedling in nursery to milk stage in main field. Symptoms appear as lesions (spots) on the coleoptile, leaf blade, leaf sheath, and glume, being most prominent on the leaf blade and glumes.
2. The disease appears first as minute brown dots, later becoming cylindrical or oval to circular The several spots coalesce and the leaf dries up.
3. The seedlings die and affected nurseries can be often recognised from a distance by their brownish scorched
Remove and destory the weed hosts in the field bunds and channels.
Seed Treatment: with Carbendazim 50 WP or Beam (Tricyclazole) @ 2 gm/kg seed.
Seed treatment with biocontrol agent: Trichoderma viride@ 4g/kg or Pseudomonas fluorescens @ 10g/kg of seed.
Avoid close spacing of seedlings in the main field.
Spray the nursery with Carbendazim 25 g or Edifenphos 25 ml for 8 cent nursery.
Spray 0.1% solution of Carbendazim 50 WP (@ 1 gm/lt water) or 0.06% Beam (Tricyclazol