Rice Swarming Caterpillar
Spodoptera mauritia
📖 Description
Rice Swarming Caterpillar (also called Armyworm or Paddy Armyworm) is a sporadic but devastating outbreak pest of rice across the Indian subcontinent, particularly in coastal and delta regions. Adult moths migrate long distances and lay eggs in masses on rice leaves. Young larvae feed gregariously, skeletonizing leaves; older larvae disperse and ‘swarm’ across fields at night, completely defoliating young rice crops. Outbreaks typically occur in years with prolonged drought followed by heavy monsoon rains, when natural enemy populations are suppressed and grassy weeds (alternate hosts) proliferate. Early detection through light trapping and weekly monitoring, combined with field drainage and biological control, is essential for outbreak management.
⚠️ Symptoms to watch for
- Skeletonized leaves and cut seedlings in patches
- complete defoliation of seedbeds
- frass on remaining plant parts
- swarming larvae visible at night
- plants sheared off at base in severe cases
🩹 Treatment
- Drain field water to expose larvae
- apply neem oil 5ml/L in evening
- set up light traps @ 1/ha
- apply Bacillus thuringiensis @ 2g/L
- use recommended insecticides at early infestation
🌿 Organic treatments
- Drain field water to expose larvae
- apply neem oil 5 ml/L in evening
- set up light traps @ 1/ha
- apply Bacillus thuringiensis @ 2 g/L
- handpick gregarious larvae at night
- apply NPV @ 250 LE/ha
- broadcast ash and lime mix
🧪 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
- Quinalphos 25 EC @ 1 ml/L
- Spinosad 45 SC @ 0.5 ml/L (apply in evening when larvae are active)
🛡️ Prevention
- Inspect seedbeds weekly
- drain field water during infestation
- control grassy weeds
- set up light traps during moth flights
- conserve predatory bugs and birds
- avoid excessive nitrogen
- deep plough after harvest to expose pupae
- monitor weather for conditions that trigger swarming (drought followed by heavy rain)
🪴 Affected plants
- Rice (Seedbeds and Young Crops)
- Maize
- Sugarcane
- Some Grasses (Poaceae)
🦋 Natural predators
- Predatory Bugs
- Spiders
- Birds
- Frogs
- Ground Beetles
- Parasitic Wasps
🌱 Host plants
- Oryza sativa
- Zea mays
- Saccharum officinarum
- Echinochloa spp.
- Leersia hexandra
🔄 Lifecycle
- Female lays 300-1000 eggs in masses covered with scales on leaves.
- Eggs hatch in 3-5 days.
- Larvae feed for 14-25 days, passing through 6 instars.
- Pupation occurs in soil, lasting 7-14 days.
- Adults live 7-15 days.
- Total life cycle 25-40 days; 4-6 generations per year.
📅 Season
- Sporadic outbreaks during Jul-Sep with onset of monsoon, particularly after drought
🔎 Appearance
- Adults are dark brown moths with a distinctive white streak on forewings.
- Larvae are dark greenish-brown with white dorsal and lateral stripes, growing up to 35 mm.
- Young larvae feed gregariously and 'swarm' across fields at night.
💥 Damage level
- High
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- Southeast Asia
- East Asia
- Australia
- Pacific Islands
Have an Insect to Identify?
Upload or take a photo of an insect on your plant and our AI will identify it and recommend treatments.
📷 Diagnose from Image