Rice Grassy stunt disease : Rice grassy stunt virus

Symptoms:

• Diseased hills are severely stunted with excessive tillering and a very upright growth habit
• Diseased hills has a grassy and rosette appearance
• Leaves short, narrow and yellowish green with numerous small rusty spots or patches, which form blotches
• Retention of green coloration of the leaves after application of sufficient nitrogenous fertilizers
• Infected plants usually survive until maturity but produce no panicles. Symptom develops 10-20 days after infection.

• The virus exists in the vector and in the rice crop. Brown plant hopper nymphs and adults transmit it where rice is grown year round. RGSV is generally endemic. The macropterous forms or the long winged adults of the insect are important in spreading the disease than the short winged forms. They feed on the diseased plant for at least 30 minutes to pick-up the virus. Higher infection is attained after prolonged inoculation feeding periods of up to 24 hours.
• The availability of the vector encourages the damage. Rice grassy stunt virus (RGSV) is a member of the Tenuiviruses. It has fine filamentous particles, which are 6-8 nm in diameter. It has a nodal contour length of 950-1,350 nm. The particles have one capsid protein and the genome is made up of four single stranded RNA.
  

Management:

• Avoid close planting .
• Grow varieties released by IRRI, which contain genes for BPH resistance, like IR26, IR64, IR36, IR56 and IR72.
• Plouging and harrowing the field to destroy stubbles right after harvest in order to eradicate other hosts

Apply any one of the following to control vector BPH

• Phosalone 35 EC 600 ml/acre
• Acephate 75 SP 250 ml/acre
• Chlorpyriphos 20 EC 500 ml/acre

Source of information:

• AICRIP rice, TNAU, Coimbatore, Rice diseases- online resource, IRRI, Phillippines.

Acknowledgements:

• IRRI, Phillippines