Rice Armyworm
Mythimna separata
📖 Description
Rice Armyworm (also called Rice Ear-cutting Caterpillar) is a sporadic but serious outbreak pest of rice across the Indian subcontinent. Adult moths migrate long distances, and females lay eggs in masses between leaves. Young larvae scrape leaf tissue, while older larvae defoliate plants, cut panicles from the stem, and feed on developing grains. Outbreaks typically occur in years with prolonged drought followed by heavy rainfall, when natural enemy populations are suppressed. Large areas of rice can be defoliated within days during outbreaks. Early detection through light trapping and weekly monitoring, combined with conservation of natural enemies, is essential for outbreak prevention.
⚠️ Symptoms to watch for
- Skeletonized leaves and cut panicles
- defoliation in patches
- feeding on developing grains
- hidden larvae in leaf whorls during day
- frass at base of plants
- severe defoliation in outbreak years
🩹 Treatment
- Apply neem oil 5ml/L
- dust carbaryl 10% on foliage in evening
- drain field water to expose larvae
- set up light traps @ 1/ha
- deep plough after harvest to expose pupae
🌿 Organic treatments
- Drain field water to expose larvae
- apply neem oil 5 ml/L
- set up light traps @ 1/ha
- apply Bacillus thuringiensis @ 2 g/L in evening
- release predatory bugs
- handpick gregarious larvae
- apply Metarhizium anisopliae
🧪 Chemical treatments
- Chlorantraniliprole 18.5 SC @ 0.3 ml/L
- Emamectin benzoate 5 SG @ 0.5 g/L
- Lambda-cyhalothrin 5 EC @ 1 ml/L
- Carbaryl 50 WP @ 2 g/L
- Quinalphos 25 EC @ 1 ml/L
🛡️ Prevention
- Synchronous planting
- deep plough after harvest to expose pupae
- control grassy weeds
- drain field during infestation
- conserve predatory bugs and birds
- use light traps during moth flights
- avoid excessive nitrogen
- monitor crops weekly during tillering
🪴 Affected plants
- Rice
- Maize
- Sorghum
- Wheat
- Sugarcane
- Oats
- Barley
- Grasses
🦋 Natural predators
- Predatory Bugs
- Spiders
- Birds
- Frogs
- Ground Beetles
- Parasitic Wasps
🌱 Host plants
- Oryza sativa
- Zea mays
- Sorghum bicolor
- Triticum aestivum
- Saccharum officinarum
🔄 Lifecycle
- Female lays 300-1500 eggs in masses on leaves.
- Eggs hatch in 4-7 days.
- Larvae feed for 15-25 days, passing through 6 instars.
- Pupation occurs in soil, lasting 7-14 days.
- Adults live 7-15 days.
- Total life cycle 30-45 days; 4-6 generations per year.
📅 Season
- Aug-Oct during Kharif rice, sporadic outbreaks during drought years
🔎 Appearance
- Adults are yellowish-brown moths with a dark speck on each forewing and a darker renal mark.
- Larvae are greenish-brown with a dark dorsal stripe and two lateral stripes, growing up to 40 mm.
- They hide in soil or leaf sheaths during the day.
💥 Damage level
- High
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- Southeast Asia
- East Asia
- Australia
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