Rice ragged stunt

Causal agent:  Ragged stunt virus   

The brown plant hopper transmits the disease. The early in star nymphs of the insect are more efficient in transmitting the disease than older ones. Five-day-old nymphs are the most efficient transmitters. The virus is acquired within a feeding period of 24 hours.

Viral particles are 63-65 nm in diameter and consist of five proteins. They are mostly found in phloem and gall cells. The genome consists of ten double-stranded RNA segments.

The virus is circulative and propagative in the insect vectors.

Symptoms:

1. Infected plants severely stunted during early growth stages of the crop
2. Leaves short and dark green with serrated edges
3. Leaf blades twisted at the apex or base, which result in the spiral shape of the leaves
4. Leaf edges uneven and the twisting give the leaves a ragged appearance
5. Ragged portions of the leaves are yellow to yellow-brown
6. Vein swellings develop on the leaf blades and sheaths
7. Swellings pale yellow or white to dark brown
8. Flag leaves twisted, malformed, and shortened at booting stage
9. Flowering is delayed
10. Incomplete panicle emergence
11. Nodal branches produced at upper nodes
12. Partially exerted panicles and unfilled grains

Management practices:

1. There are no specific control measures for the ragged virus disease except for the use of resistant varieties.
2. Because some rice varieties are resistant to the brown plant hopper, to the virus, and to both.
3. Cultivars resistant to the vector have low disease incidence.
4. The application of insecticides to migratory plant hoppers is being used in temperate countries to reduce disease incidence.