Tungro disease of rice, it’s Economic Importance & Management Practice’s

Rice Tungro Disease(RTD): Rice tungro bacilliform virus & Rice Tungro Spherical virus

Economic importance

The mentak disease of Indonesia is also identified as Tungro. Tungro is commonly found in Bangladesh and India. In India, it is seen in states of West Bengal, Kerala and other parts of India. Tungro is one of the most widely distributed and most destructive diseases in tropical Asia. The loss was estimated during 1940 as 30% or 1.4 million hectares annually. In Thailand a severe epidemic occurred in 1966 affecting more than 3 lakh hectares. An
outbreak of Tungro in 1971 affected hudred and thousands of hectares in Phillippines. In Nepal Rice Tungro virus which is commonly known as rate rot (red disease )Or tungro which was firstly reported from parawanipur of Bara
district. Rice tungro virus disease infected plants gave 88.9% of loss grain than that of grain from healthy plants. The loss upto 22.9% is obtained due to shorter plant height, 16.3 % from smaller panicles, 67% from smaller number of effective tillers and 85.9% from lesser filled grains when plants are infected by tungro virus compared to that of healthy plants.

Symptoms

Infection occurs both in the nursery and in the main field. Plants are markedly stunted. Stunting is more severe on susceptible varieties and slight on more resistant varieties. Leaves show yellow to orange discoloration and interveinal chlorosis. Yellow discoloration is commonly seen in “Japonica” varieties, while “Indica” varieties show orange discoloration. Yellowing starts from the tip of the leaf and may extend to the lower part of the leaf blade. Young leaves are often mottled with pale green to whitish interveinal stripes and the old leaves may have rusty streaks of various sizes. The plants may be killed if infected early. Tillering is reduced with poor root system. The infected plants have few spikelets and panicles are small with discoloured grains.

Special detection techniques :

Collect leaf samples early morning before 6 a.m.

The top 10 cm portion of the leaf is immersed in a solution containing 2g of iodine and 6g of potassium iodide in
100ml of water for 15-30 minutes or 10 ml of tincture iodine + 140 ml of water for one hour, washed in water and
when examined.

Tungro infected leaves develop dark blue streaks.

Disease cycle
The virus causes severe damage only in area where the host plants and the insect vector multiply the year round. In the areas where the rice is not grown continuously, collateral hosts, especially wild rice are probable sources of
inoculum. Stubbles of infected plants from the previous season also serve as a source of inoculum. Grassy weeds such as Eleusine indica, Echinochloa colonum, Echinochloa crusgalli may be infected occasionally. The leafhoppers
viz, Nephotettix virescens, N. nigropictus, N. parvus, N.malayanus and Recilia dorsalis transmit the virus in a non-persistent manner.

Management of Rice tungro virus :

Cultural methods :

Summer deep ploughing and burning of stubbles.

Destroy weed hosts of the virus and vectors.

Grow disease tolerant cultivars .

Need seed cake applied at 5 kg/0.032ha of nursery followed by foliar spray of 5% neem karnal extract in main field reduces vector or population and incidence of tungro.

Mechanical methods:

Light traps are to be set up to attract and control the leaf hopper vectors as well as to monitor the population.
This should be practiced every day.

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 resistance also because of high potassium content.

Green leaf hoppers as vectors are to be controlled effectively in time by spraying.

Spray insecticides twice, 15 and 30 days after transplanting

Spray two rounds of any one of the following insecticides :
Monocrotophos 36 wse (40ml/ha)
Fenthion 100 EC (40ml/ha) may be sprayed 15 & 30 days after transplanting. The vegetation on the bounds should also be sprayed with the insecticides. Maintain 2.5 cm of water in the nursery and broadcast anyone of the following is 20 cents, Carbofuran 3G 3.5 kg or phorate 10G 1.0 kg or Quinalphos 5G 2kg in nursery when virus infection is low. Apply Carbofuran granules @1kg/ha to control population.

During pre-tillering to mid-tillering when one affected hill/m is observed apply Carbofuran granules @3.5kg/ha or spray Monocrotophos @1.6 to 2.2ml/lit to control insects vector.

Biological methods :

Two fungi,Beauveria bassiana & paecilomyces a moeneroseus are reported as parasites of rice green leaf hopper, Nephotettix virescence. Spray of conidias suspension of the fungi on rice plants kills the
vector.

Causal Organism Biocontrol agents
Tungro – Rice Tungro virus – P. Fluorescence
Vector – Nephotettix ssp. For vector

Writer : Sirpat Badhai, Bsc (hons)Ag from institute of agricultural sciences Banaras Hindu university u.p.221005, India