Mustard Sawfly
Athalia lugens proxima
📖 Description
Mustard Sawfly is a major pest of mustard and other Brassica oilseed crops across the Indian subcontinent, particularly in Rajasthan, Uttar Pradesh, Madhya Pradesh, Haryana, and Punjab. Adults are wasp-like insects that lay eggs inside leaf tissue. Larvae feed gregariously on leaves, eating round holes and skeletonizing leaves. Heavy infestation can defoliate entire fields, reducing photosynthesis and yield. The pest is most damaging to seedling crops in October-November when plants are small and vulnerable. Unlike Lepidopteran caterpillars, sawfly larvae have 8 pairs of prolegs (more than 5 pairs in caterpillars) and can be distinguished by their gregarious feeding behavior and characteristic defensive posture (curling the rear end over the back). Deep ploughing after harvest exposes overwintering pupae in soil to predators and sun, reducing carryover populations.
⚠️ Symptoms to watch for
- Round holes in leaves
- skeletonized leaves with only veins remaining
- defoliation in patches
- damaged leaves appear net-like
- stunted plants in heavy infestation
- yield loss 30-50% in severe cases
🩹 Treatment
- Handpick larvae in small plots
- apply neem oil 5ml/L
- dust carbaryl 10% on foliage
- apply recommended insecticides at early larval stage
- deep plough after harvest to expose pupae
🌿 Organic treatments
- Handpick larvae in small plots (drop into kerosenated water)
- apply neem oil 5 ml/L with sticker
- spray 5% NSKE
- apply Bacillus thuringiensis @ 2 g/L
- apply Beauveria bassiana @ 5 g/L
- deep plough after harvest to expose pupae
- light traps @ 1/ha for adult monitoring
🧪 Chemical treatments
- Dust Carbaryl 10% @ 25 kg/ha on foliage
- spray Quinalphos 25 EC @ 1 ml/L
- Dichlorvos 76 EC @ 1 ml/L
- Lambda-cyhalothrin 5 EC @ 1 ml/L
- Indoxacarb 14.5 SC @ 1 ml/L (apply at early larval stage)
🛡️ Prevention
- Plant early to escape peak larval activity
- deep plough after harvest to expose overwintering pupae in soil
- handpick larvae in small plots
- monitor adult activity with light traps
- rotate with non-Brassica crops
- balanced fertilizer use
- conserve predatory bugs and birds
- inspect crop weekly during seedling stage when damage is most critical
🪴 Affected plants
- Mustard
- Rapeseed
- Toria
- Sarson
- Taramira
- Other Brassicas
- Sometimes Radish and Turnip
🦋 Natural predators
- Spiders
- Predatory Bugs
- Birds
- Frogs
- Parasitic Wasps
- Ground Beetles
🌱 Host plants
- Brassica juncea
- Brassica napus
- Brassica rapa
- Eruca sativa
- Raphanus sativus
🔄 Lifecycle
- Female lays 30-150 eggs singly inside leaf tissue using her saw-like ovipositor.
- Eggs hatch in 4-7 days.
- Larvae feed for 10-18 days, passing through 5-6 instars.
- Mature larvae drop to soil and pupate in earthen cocoons, lasting 10-20 days (or overwinter for 3-4 months).
- Adults live 7-15 days.
- Total life cycle 25-40 days; 3-5 generations per year.
📅 Season
- Active Oct-Mar during Rabi oilseed season, peaks Nov-Dec on seedling crops
🔎 Appearance
- Adults are small, orange-yellow wasp-like insects with black markings on the head and thorax.
- Larvae are dark greenish-black with a glossy black head and 8 pairs of prolegs (more than caterpillars which have 5 or fewer pairs), growing up to 16 mm.
💥 Damage level
- High
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- East Asia
- Southeast Asia
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