Rice Blast( Pyricularia grisea )

Symptoms

• Noticed generally on leaves, nodes, panicles and grains, and rarely on leaf sheath.
• Leaf blast:- Symptoms appear as minute brown specks at first,which enlarge to form spindle shaped lesions with pointed ends in susceptible cultivars.
• The centre of the spot is grey or white with brown or reddish brown margin and with conspicuous yellow halo around the spots.
• Fully developed lesions are 1 to 1.5 cm in length and 0.3 to 0.5 cm in width. However, in resistant cultivars only minute brown pinheads are noticed.
• Heavily infected leaves soon become blighted and die.
• Nursery blast:- Severe infection in the nursery stage causes death of seedlings.
• Badly affected nurseries can be recognized from a distance by their brownish, scorched appearance.
• Node blast:- When infection occurs on nodes it rots leading to death of the parts above the node.
• The most destructive phase of the disease is when the pathogen infects panicles.
• Neck blast:- The symptom is characterized by the appearance of black or grayish brown lesions at the base of the panicle(neck).
• If the symptoms occur at the time of panicle emergence, entire grains of the panicle turn chaffy.
• The attack at later stages,causes partly filled grains.
• Brown to black spots is also sometimes seen on the infected glumes.

Management

• Use certified and healthy seeds. Kanchana, Makom, Onam, Swarnaprabha, Athira, Aiswarya, Jaya, IR-8 etc. are resistant varieties.
• Remove and destory the weed hosts in the field bunds and channels.
• Avoid excess use of nitrogenous fertilizers.
• Seed treatment with Pseudomonas fluorescens (10 g/litre of water for 1 kg of seed), seedling dipping in and prophylatic spraying of Pseudomonas fluorescens (20 g/litre of water) is effective in preventing the incidence of the disease.
• Soak seed for 12 to 16 hours in Carbendazim 50 WP (2 gram / kg of seed per litre of water).

Chemical Control

Sl.No	Generic Name	Trade Name	Color code	Dosage/litre	Knapsack Sprayer (Capacity 10L)	Dosage/acre (200 L)	Dosage/hectare (500 L)	Remarks
1	Carbendazim 50 WP	Bavistin, Benfil, Bengard, Benlate, Benmain, Bensaan, Carben, Carziim50, Dhanustin, Dhanustin 50 WP, Fungiguard, Gancarzin50, Glizim, Mintho, Tagstin, Tiara, Zoom	Green	1 g/ litre of water	10 g	200 g	500 g
2	Carpropamid 27.8 SC	Arcado , Protega	Green	1 ml/ litre of water	10 ml	200 ml	500 ml
3	Isoprothiolane 40 EC	Fuji-one 40 E, Isomain, Rhizo M-45 Manzate, Luzen-45, Macoban, Macoban M-45, Mancosaan, Mancosaan M-45, Maneb Manzane, M-Guard, Savour M 45, Tata M-45 Eurofil-NT, Uthane M-45, Veera, Zinthane	Blue	1 ml/ litre of water	10 ml	200 ml	750 ml
4	Tebuconazole 25.9 EC	Folicur, Orius, Tebustar	Blue	1-1.5 ml/ litre of water	10-15 ml	200-300 ml	500-750 ml
5	Hexaconazole 5 EC	Alert Creeper, Contaf, Corazole, Danzole, Force 5C, Hexaan, Hexacone, Hexadhan, Hexamax, Hexan, Hexazole, Mainex EC, Sitara, Strike, Titan, Topper, Topper plus EC, Xantho	Blue	1 ml/ litre of water	10 ml	200 ml	500 ml

Extremely Toxic

Highly Toxic

Moderately Toxic

Slightly Toxic