Rice diseases and their control

Rice is one of the world’s major food crops. Rice is the staple food of more than half of the world’s population, so we must know about rice diseases and their control measures. Here we will know in detail about the diseases of rice, their symptoms, management and prevention measures.

Brown spot of rice

Brown spot of rice is caused by a fungus called Helminthosporium oryzae. It is a seed borne disease. In paddy crop, this disease can occur at any time from the seedling stage to the stage of grain formation.This disease occurs more commonly in potash deficient soil.This disease attacks the leaves and grains of plants, but the symptoms of the disease are more clearly visible on the leaves.

Symptoms

• Small, sesame shaped round or oval brown spots are formed on the leaves.
• A yellow circle is formed around these spots and the center of the spots is yellowish brown in color.
• As the disease progresses, the spots coalesce, enlarge and spread over the entire leaves and eventually the leaves dry up.
• Brown or black spots are also formed on the peels of the grains, due to which the grains appear discolored.

Management/control

• Use a balanced amount of plant nutrients (fertilizers) in the field.
• Sow the seeds after treating them with a fungicide.
• Spray Dithane M-45 (0.2%) or Dithane Z-78 (0.25%) solution to control the disease.

Rice blast

Rice blast is caused by a fungus called Magnaporthe grisea. Rice blast disease is also known as rotten neck and rice fever. This disease was first recorded in India in the year 1918. This disease is found in about 80 rice growing countries. In case of severe infestation of this disease, crop loss can be up to 70-80%.

Symptoms

The disease affects the leaves, nodes and neck (base of the panicle) of the plant but the symptoms of the disease are more clearly visible on the leaves.

Leaf blast
First small specks are formed on the leaves, later these specks enlarge and appear on the leaves as a spindle or eye shape (0.5 to 1.5cm length, 0.3 to 0.5cm width). The edges of these spots are brown in color and the middle part is gray in color. Later, many spots coalesce and form large irregularly shaped spots on the leaves, due to which the leaves get scorched and dry up.

Neck blast
In neck blast, the base of the panicle shrinks and dark spots are formed all around. If this type of infection occurs before the earrings emerge, then the earrings come out straight and the granules in the earrings are partially formed or not completely formed. But if the infection occurs after the emergence of earrings, then the panicle breaks and hangs due to the death of the tissues, which can cause a huge loss of grains.

Node blast
The nodes of the plants affected by the disease turn black and break.

Management/control

• Sow healthy seeds and transplant disease-free seedlings only.
• Nursery should not be grown in shady areas.
• Use balanced amount of fertilizers, avoid excess Nitrogen.
• Sow disease-resistant varieties like IR-64, Pusa Basmati-1637, Pankaj, Jamuna, and Pantadhan-10.
• Do not use nitrogenous fertilizer when symptoms of the disease appear.
• Seed should be sown after treating with Carbendazim 50% WP @ 2g/kg of seed.
• Spray the following chemicals when symptoms of the disease appear:
  • Carbendazim 50 wp @500g/ha  Or
  • Tricyclazole 75 wp @500g/ha Or
  • Metominostrobin 20 sc @500 ml/ha Or
  • Azoxystrobin 25 sc @500ml/ha

Tungro disease of rice

Tungro disease of rice is caused by viruses called Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV). In paddy, this disease is transmitted by leafhoppers. Where green leafhoppers are responsible for transmitting most diseases. Tungro disease affects the crop at all stages of growth but most commonly at the stage of vegetative growth.

Symptoms

• The growth of the plants affected by the disease is stunted and tillerings are also reduced.
• Older leaves begin to turn orange-yellow at the tips and extend down to the lower leaf portion.
• Flowering is delayed and small and weak panicles are also formed, which are dark brown in color.

Management/control

• In areas where the disease spreads more, crop rotation of oilseeds or leguminous crops should be adopted.
• After harvesting, do deep plowing to destroy stubbles.
• Light traps can be installed to attract and control leafhoppers.
• Spray Thiamethoxam 25 WDG 100g/ha or Imidacloprid 17.8 SL 100ml/ha at 15 and 30 days after transplanting of paddy.
• Spray insecticide on the weeds of the bunds as well.
• To reduce the yellowing of leaves caused by disease, spraying can be done by mixing 2% urea solution with Mancozeb 2.5 g/liter solution.

Khaira disease of rice

Khaira disease of rice is caused by the deficiency of zinc. Khaira disease of rice is a physiological disorder. In this disease, the lower leaves of the plants start turning yellow and after that, brown spots appear on the leaves. In case of severe outbreak of the disease, the leaves start drying. Plant growth is stunted and tillering is reduced. Symptoms of khaira disease are seen more in high yielding varieties of paddy.

Management/control

• To avoid the problem of this disease, 25 kg zinc sulfate per hectare should be applied before transplanting at the time of preparation of the field.
• For the control of Khaira disease, spraying of 5 kg Zinc Sulfate and 2.5 kg Lime in 600-700 liters of water per hectare should be done when the initial symptoms of the disease appear.
• If the disease is still not under control, then 10 days after the first spray, the second spray should be done at the same rate.
• Transplanting after soaking the ‘roots of plants’ in 2% zinc sulfate solution for 1-2 minutes is also beneficial.

Bacterial leaf blight

Bacterial leaf blight of rice is a bacterial disease, caused by Xonthomonas oryzae pv. oryzae. This disease can occur at any time from the seedling stage to the mature stage of the plants.

Symptoms

• In this disease, long dry lesions begin to form from the tip of the leaf and move towards the central part of the leaf through the edge.
• Wavy spots appear on the edges of the leaves.
• In case of severe infestation of the disease, the entire leaf dries up.

management/control

• Water should be drained from the field when symptoms of the disease appear.
• Use a balanced amount of fertilizers.
• If the crop shows signs of disease, apply less amount of nitrogen fertilizers.
• Sow only healthy and treated seeds.
• For the control of bacterial leaf blight, spray 75 grams of ‘Agrimycin-100’ and 500 grams of copper oxychloride in 700-800 liters of water per hectare.
• If ‘Agrimycin-100’ is not available, 100 g streptocycline can be used instead.

Sheath blight of rice

Sheath blight of rice is caused by a fungus called Rhizoctonia solani. The symptoms of this disease start appearing from the paddy nursery. After planting in the field, the symptoms of the disease appear at the last stage of tillering.

Symptoms

• In this disease, irregularly shaped spots are formed on the leaf sheath just above the ground or water surface.
• These spots are 2-3 cm long, green to brown in color, which later become straw colored (pale yellow color).
• Purple stripes are formed around the spots.
• In severe outbreak of disease, the mycelium is clearly visible on the lesions, on which semi or fully spherical brown sclerotia are formed.
• Circular spots are formed on the leaves.
• Under favorable conditions, many small spots coalesce to form large spots, due to which the sheath, stem, leaves become completely affected; Eventually the plants die.

Management/control

• Keep fields and bunds weed free.
• Use a balanced dose of fertilizers and apply the total amount of nitrogen in 2-3 times.
• Sow only healthy and treated seeds.
• Sow the seeds after treating with Carbendazim 50% wp @ 2 g/kg of seed.
• If the crop shows signs of disease, spray 1 kg Carbendazim or 1 liter Hexaconazole in 600-700 liters of water per hectare.

Note: Any recommendations regarding the use of chemicals are for informational purposes only. Before using any type of chemical for weed, disease and pest control, consult the nearest agriculture shop or a local agricultural consultant.

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