RICE

Sown across 45 million hectares as India’s primary kharif crop, rice is the food security anchor of eastern, southern, and coastal India.

5 Major Threats and Their Control

For educational purposes only. Recommended crop varieties are location-specific. Always verify chemical and variety recommendations with your local KVK or State Agriculture Department.

1. Blast Disease

(Magnaporthe oryzae)

The Threat:

  • Rice blast is the most destructive fungal disease of rice worldwide.
  • The pathogen attacks all above-ground parts of the plant — leaves, nodes, and panicle neck — but is most devastating during the seedling and panicle-filling stages.
  • On leaves, it produces distinctive grey, diamond-shaped lesions with brown margins.
  • At the node stage, it can girdle individual nodes and kill the entire branch above.
  • When it attacks the panicle neck (“neck blast”), it severs the nutrient supply, causing grains to remain empty and hollow even on a visually healthy-looking plant.
  • The disease spreads explosively under high humidity, prolonged leaf wetness, and cool nights below 24°C.
  • It can cause 10–30% yield loss in a single season.

The Solution:

  • Grow blast-resistant varieties as recommended by ICAR-NRRI, Cuttack, and the state agricultural universities for your specific agro-climatic zone — resistance ratings change as new pathogen races emerge, so always get the current season’s variety advisory.
  • Maintain adequate silicon nutrition through silica-rich organic matter or slag application; silicon physically toughens leaf cell walls against fungal penetration and is one of the most cost-effective preventive measures available.
  • At the first appearance of leaf lesions or at panicle emergence in blast-prone areas, spray Tricyclazole 75 WP (Systemic Fungicide — Melanin Biosynthesis Inhibitor, FRAC Group U1) @ 0.6 g/litre of water.
  • A second spray at full panicle emergence is recommended in high-humidity seasons.

2. Brown Planthopper

(Nilaparvata lugens)

The Threat:

  • The Brown Planthopper (BPH) forms dense colonies at the base of rice plants and sucks phloem sap directly from the stem, depleting the plant’s carbohydrate reserves faster than they can be replenished.
  • The result is “hopperburn” — the plant turns yellow, then brown, appears scorched, and dies in circular patches across the field.
  • BPH thrives in humid, shaded environments created by dense planting and excessive nitrogen use, and is most active from the booting to the maturity stage.
  • Broad-spectrum insecticide sprays made on a calendar basis destroy natural enemies such as spiders and mirid bugs, which normally regulate BPH populations.
  • This leads to explosive outbreaks that are often worse than if no intervention had been made.

The Solution:

  • Prevention begins with cultural management — use BPH-resistant varieties developed by ICAR such as Ptb-33 derivatives, MTU-7029, and Swarna; maintain 30 cm row spacing; reduce nitrogen below excessive levels; and drain fields intermittently to disrupt the pest’s preferred environment.
  • Conserve natural enemies at all times, particularly spiders, which are highly effective predators and should never be sacrificed to a prophylactic spray.
  • Monitor the base of plant stems weekly, not the top of the canopy.
  • Apply a chemical spray only when the population crosses the Economic Threshold Level of 1 hopper per tiller (where no predators are visible) or 2 per tiller (where spiders are present).
  • Use Buprofezin 25 SC (Insecticide — Insect Growth Regulator, IRAC Group 16) or Pymetrozine 50 WG (Insecticide — Feeding Blocker, IRAC Group 9B) directed at the base of the plant.
  • Never apply pyrethroids (IRAC Group 3A) — they are the primary cause of BPH resurgence by eliminating natural enemies.

3. Khaira Disease

(Zinc Deficiency)

The Threat:

  • Khaira is the visible expression of zinc deficiency in transplanted rice — rusty-brown spots and bronzing appear on young leaves within 2–3 weeks of transplanting.
  • Plant growth slows dramatically, and the crop remains stunted throughout the season with reduced tiller number and poor panicle initiation.
  • It is most common in the calcareous (alkaline) and waterlogged soils of eastern India, where zinc is chemically immobilised at high pH and is unavailable to roots even when adequate amounts are present in the soil.
  • Severe Khaira can reduce yield by 10–20% and is frequently misdiagnosed as a disease.

The Solution:

  • Apply Zinc Sulphate (ZnSO₄) 21% (Micronutrient Fertiliser) @ 25 kg/ha as a basal dose in both the nursery bed and the main field before transplanting — this is the ICAR-recommended standard for zinc-deficient rice soils.
  • For visible symptoms in a standing crop, spray a 0.5% ZnSO₄ solution (5 g per litre of water) on young plants twice, at a 15-day interval, ensuring thorough coverage of young leaves.
  • Maintaining soil organic matter through FYM incorporation naturally improves zinc solubility and availability across seasons.
  • Soil testing for available zinc every 3 years allows precise, need-based application.

4. Bacterial Leaf Blight

(Xanthomonas oryzae pv. oryzae)

The Threat:

  • Bacterial Leaf Blight (BLB) spreads most aggressively when strong winds and continuous heavy rain carry bacterial cells through water droplets from lesion to lesion across a field.
  • It causes water-soaked, yellow-to-white stripes along leaf margins that progressively dry from the tip downward — a symptom easily confused with drought damage in early stages.
  • In seedlings, it can cause complete wilting — the “kresek” symptom — destroying transplanted crops before they establish.
  • The disease peaks between 25–34°C with humidity above 70%, and is dramatically worsened by excessive nitrogen application, which produces the lush, dense canopy the bacteria multiply in.
  • Yield losses can reach 20–30% in severe cases, with quality losses even in milder infections.

The Solution:

  • There is no reliable curative spray once BLB is well established — prevention and crop management are the only effective tools.
  • Grow resistant varieties recommended by ICAR — IR-64, Pusa Basmati-1, and Improved Samba Mahsuri carry field-level BLB resistance.
  • Apply nitrogen in moderate, split doses and never exceed the recommended level for your variety.
  • Maintain good field drainage and keep fields clean of weed hosts and rice ratoons that serve as bacterial reservoirs between seasons.
  • Allow fallow fields to dry completely before the next crop to reduce soil-borne bacterial populations.
  • For nursery protection in high-risk areas, use Streptomycin Sulphate 90% + Tetracycline Hydrochloride 10% SP (Bactericide — Antibiotic combination) as seed treatment or nursery spray, or Copper Oxychloride 50 WP (Bactericide / Contact Fungicide — Inorganic Copper) as a preventive foliar spray applied before symptom onset.
  • Kasugamycin 3 SL (Bactericide / Fungicide — Antibiotic, registered for both BLB and blast) is also recommended by ICAR for dual-purpose management in high-pressure seasons.

5. Deep Flooding / Submergence

The Threat:

  • Complete submergence of the rice crop for more than three days — a regular annual event in the flood-prone districts of Assam, Odisha, Bihar, and eastern Uttar Pradesh — can destroy a standing crop entirely, particularly at the vulnerable tillering stage.
  • The oxygen-deficient (anaerobic) conditions created by deep flooding weaken root systems and sharply reduce the number of productive tillers that will eventually bear grain.
  • Flooding creates a warm, stagnant environment in which fungal and bacterial diseases amplify rapidly after flood recession.
  • Prolonged water stagnation leaches key nutrients — particularly nitrogen and potassium — from the root zone.
  • Submergence stimulates methane production by soil microbes, making this both an agronomic and an environmental concern.

The Solution:

  • The most reliable response is varietal — ICAR’s IRRI collaboration produced submergence-tolerant varieties carrying the Sub1 gene, of which Swarna-Sub1 is the most widely adopted, capable of surviving up to 14 days of complete submergence without significant yield loss under Indian field conditions.
  • FR43B and Ciherang-Sub1 are additional options for specific states.
  • Maintain well-constructed field bunds to control the depth and duration of flood entry.
  • Practice Alternate Wetting and Drying (AWD) water management between flood events — allowing the field to partially dry before re-flooding improves root aeration, enhances nutrient uptake efficiency, and measurably reduces methane emissions, a benefit recognised under India’s National Action Plan on Climate Change.
  • There is no chemical intervention for submergence damage — varietal and structural preparedness is the only reliable protection.
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