Agricultural crops :: Cereals :: Rice
Identification of Pathogen:
- Tungro virus disease is transmitted by leafhoppers, wherein the most efficient vector is the green leafhopper,Nephotettix virescens . The disease complex is associated with rice tungro baciliform virus (RTBV) and rice tungro spherical virus (RTSV). RTBV cannot be transmitted by leafhoppers unless RTSV is present.
- Insects could acquire the virus from any part of the infected plant. After acquiring the virus, the vector can immediately transmit to the plants.
- RTBV particles are rod-shaped and 100-300 nm in length and 30-35 nm in width. It contains DNA of 8.3 kb. RTSV particles are isometric and 30 nm in diameter. It has a polyadenylated single-stranded RNA of about 12 kb.
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Management:
Trap methods:
- Light traps are to be set up to attract and control the leaf hopper vectors as well as to monitor the population.
- In the early morning, the population of leafhopper alighting near the light trap should be killed by spraying/dusting the insecticides. This should be practiced every day.
Cultural methods:
- Planting of resistant varieties against tungro virus disease is the most economical means of managing the disease.
- Use resistant varieties like IR 36, IR 50, ADT 37, Ponmani, Co 45, Co 48, Surekha, Vikramarya, Bharani, IR 36 and white ponni .
- Among the cultural management practices, adjusting the date of planting is recommended.
- Likewise, observing a fallow period of at least a month to eliminate hosts and viruses and vectors of the disease.
- In epidemic areas follow rotation with pulses or oil seeds.
- Apply neem cake @ 12.5 kg/20 cent nursery as basal dose.
- Plouging and harrowing the field to destroy stubbles right after harvest
- Eradicate of other tungro hosts are also advisable.
- Destruction of weed hosts on bunds.
Chemical methods:
- Leaf yellowing can be minimized by spraying 2 % urea mixed with Mancozeb at 2.5 gm/lit.
- Instead of urea foliar fertilizer like multi-K (potassium nitrate) can be sprayed at 1 per cent which impart disease resistance because of high potassium content.
- Green leaf hoppers as vectors are to be controlled effectively in time by spraying.
- Vegetation on the bunds should also be sprayed with the insecticides. Maintain 2.5 cm of water in the nursery and broadcast anyone of the following in 20 cents Carbofuran 3 G @ 3.5 kg (or) Phorate 10 G @ 1.0 kg (or) Quinalphos 5 G @ 2.0 kg.
- In nursery when virus infection is low, apply Carbofuran granules @ 1 kg/ha to control vector population.
- During pre-tillering to mid-tillering when one affected hill/m is observed start application of Carbofuran granules @ 3.5kg/ha to control insect vector.
- Spray Two rounds of any one of the following insecticides
- Thiamethoxam 25 WDG @ 100 g/ha (or)
- Imidacloprid 17.8 SL @ 100 ml/ha at 15 and 30 days after transplanting. The vegetation on the bunds should also be sprayed with the insecticides.
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Source of information:
- AICRIP rice, TNAU, Coimbatore Rice diseases- online resource, IRRI, Phillippines.
Acknowledgements:
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