RICE BLAST

                                      RICE BLAST

(Pyricularia oryzae)

Mode of transmission/dissemination:  The pathogen is both seed and airborne.

Blast disease is a Fungal disease.It is most severe in areas with high humidity and rainfall.Mean max., min. temperature (26-27 and 19-10°C, respectively) and high humidity (RH 87%) or high rainfall (2766mm) during the past years favor the rapid blast development . In India Blast disease are most common in the southern part, particularly coastal areas.Excessive Dew can spread  blast disease.

Symptoms: 

• The blast is a foliage disease .
• Its all parts except root infected.   
• Disease can infect paddy at all growth stages and all aerial parts of plant (Leaf, neck and node).   

Fig: A.Leaf Blast

      Leaf Blast:

• Brownish lesion and spot are formed in the leaf blade, leaf sheath.
• The spot are spindle shaped with grey or white colour in central parts and brownish or reddish color of border.
• The spot are enlarge as the disease progresses.                       

     

        

      Rice collars:

• Symptoms of infection of the collars consist of a general area of necrosis at the union of the two tissues.
• Collar infections can kill the entire leaf and may extend a few millimeters into and around the sheath.               

        Neck Blast:

• Neck blast is the most destructive phase of the disease
• bluish patches are shown on the neck or stem.
• If infection of the neck occurs before milky stage, no grain is formed, but if infection occurs later, poor quality grains are formed.
• If infection of the neck occurs before milky stage, no grain is formed, but if infection occurs later, poor quality grains are formed.
• Neck and node blast can also cause whiteheads or white panicles, similar to stem borer infection.   

Node Blast

       Nodal Blast:  

• Node infection occurs in banded pattern. 
• Lesions on the node are blackish to grayish brown.
• Neck and node blast can also cause whiteheads or white panicles, similar to stem borer infection.

Management:

      Preventive measures:

• Use of disease free seeds.
• Use of resistant varieties like Rasi,Sasysree,kasturi,Gauthami, IR-36, IR-64, Parijatha,IR-20,KHITISH,  SAMBA-MASURI, etc.
• Adjustment of sowing time to avoid this disease. In general,the late planted crops suffer more from the blast infection.
• Avoid excess nitrogen.
• Application of fertilizer based on soil test report.

      Cultural practices:

• Apply N in three split doses (50% basal, 25% in tillering phase and 25% N in Panicle Initiation stage)
• Continuous maintenance of standing water to reduce the blast intensity.
• Silicon fertilizers (e.g., calcium silicate @120-200 kg/ha) can be applied to soils that are silicon deficient to reduce blast. (Cheap sources of silicon,such as straws of rice not removing the straw from the field following  harvest. Recycle rice straw (5-6% Si) and rice husks (10% Si).

     Biological control:

• Seedling root dip treatment with Pseudomonas fluoresces (4gm / 1 of water) for 20 min.
• Foliar spray of Pseudomonas fluorescence (4g / 1 of water) at 20-25 days after transplanting

      Chemical control:

• To treat the seeds with Carbendazim 50 % W.P @ 2gm/kg of seed or Tricyclazole 75 % W.P @ 3 g/kg of seed- dilute 2 gm of fungicide with 1.0 liter of water and soak 1 kg of seed for last 8-10 hrs, before sowing in seedbed.
• Pyraclostrobin 100 g/l @ 400 ml/acre.(Seltima) OR 
• Spray Tricyclazole 75 WP (Beam or Sivic) @ 0.6 g/l of water or 
• Spray Ediphenphos 50 EC (Hinosan) @ 1 ml/l  of water or
• Spray Iprobenphos 48 EC (Kitazin) @ 2g/l  of water or 
• Spray Isoprothiolane 40 EC (Fiji-One) @ 1.5 ml/l or 
• Spray Kasugamycin 3 SL (Kasu-B) @ 2.5 ml/litre or 
• Spray Carpropamid 300 SC (Protega) @ 1 ml/litre or
• Carbendazim 50 WP (Bavistin) @ 1 g/l.Lit Of Water.
• Spray Tebuconazole 50% + Trifloxystrobin 25% (75% WG)  @ 1.5 gm / 2 lit of water. (netivo). OR 
• Spray   Tricyclazole 18% + Mancozeb 62% ( 80% Wp) @ 2 gm  / Lit Of Water.  (Marger)
• Spray Tricyclazole 34.2% + Propiconazole 10.7% ( 44.9% Sc) @ 1 ml  / Lit Of Water.
• Tricyclazole 22% + Hexaconazole 3% SC @   1 gm/5 Lit. Water.