Rice blast is a fungal infestation known to occur in all the rice growing areas of the county. The disease attacks all the parts of the crop growing above the soil. It is broadly classified into three types, leaf, collar and neck blasts.
Initially elliptical or spindle shaped lesions occurs with brown borders and grey canters. Under favourable conditions, lesions enlarge and coalesce eventually killing the leaves. Leaf blast usually increases early in the season and then declines later as leaves become less susceptible.
Collar blast occurs when the pathogen infects the collar that can ultimately kill the entire leaf blade. The pathogen also infects the node of the stem known as node blast that turns blackish and breaks easily.
Neck blast occurs when the pathogen infects the neck of the panicle. The infected neck is girdled by a greyish brown lesion and the panicle falls over if the infection is severe. If neck blast occurs before the milk stage (rice forming stage), the entire panicle may die prematurely, leaving it white and completely unfilled.
Later infections may cause incomplete grain filling and poor milling quality.
Varietal resistant to blast is the most practical and economical approach for management. The most common resistant varieties are Aditya, CSR27, IR64, KRH2, Krishna, Hamsa, Naina, Pusa sugandha3, Rasi, Vasumati, PA6129, DRRH2, Dhan80, PR113, Swati, Narendra, Sumati, Swarnadhan, Triguna, Tulasi, IR-36 etc.
Use disease free seeds. Apply recommended dosage of nitrogen application in 3 to 4 splits and avoid final application in infested plots.
Burn previous crop residues if the crop is found infested. Early sowing helps prevent this infestation spread from neighbouring fields. Avoid water stagnation.
Treat seeds with Pseudomonas fluorescence 10g/lit of water for 30 min, dip the seedlings in Pseudomonas fluorescence 5gm/lit for 20 minutes before transplanting. Foliar spray of the Pseudomonas fluorescence 5gm/lit can be done at an interval of 15-20 days after transplanting.
(Mallikarjun Kenganal & V. R. Joshi, Assistant Professors, Plant Pathology, Agricultural Extension Education Centre, Koppal, Karnataka: 583 231, Ph: 09845364708, email: mallikarjun_nss@rediffmail. com)