Jute Stem Weevil
Apion corchori Wagner
📖 Description
Jute Stem Weevil (Apion corchori) is a serious pest of jute across the Indian subcontinent. Particularly severe in the major jute-growing belts of West Bengal (Murshidabad, Nadia, North 24 Parganas), Bihar (Purnia, Katihar), Assam, Odisha, and eastern Uttar Pradesh. India is the world’s largest jute producer with over 1.5 million tonnes annually, with the jute industry supporting over 40 lakh farm families. The pest is unusual among jute pests because (a) it is host-specific to jute — not feeding on other plants, making it a specialist pest, (b) larvae tunnel inside jute stems — making them protected from contact insecticides and biological control agents (only systemic insecticides can reach them), (c) a single female lays 30-60 eggs inside jute stems (bored with the rostrum), with larvae developing over 20-30 days inside the stem and pupating in pupal chambers within the stem, (d) larval feeding causes characteristic swollen galls (5-15 mm diameter) on the stem — disrupting nutrient and water transport and reducing fibre yield and quality, (e) the pest is most damaging during July-August (peak monsoon — exactly when jute plants are in active vegetative growth), and (f) the pest persists year-round on volunteer jute plants and in crop residue — making crop sanitation essential for control. IPM with early planting, resistant varieties (tossa jute less susceptible), crop rotation, crop residue destruction, neem cake soil application, light trap monitoring, biological control (limited efficacy on larvae inside stems), and need-based systemic insecticide application (carbofuran, monocrotophos — hazardous, use sparingly) provides effective control. The pest is a particular concern for Indian jute farmers because (i) India is the world’s largest jute producer, (ii) larvae are protected inside jute stems — making control difficult and requiring hazardous systemic insecticides, (iii) the pest is most damaging during July-August (peak monsoon — exactly when jute is in active growth and when field operations are most difficult), (iv) much Indian jute farming is done by small and marginal farmers with limited access to IPM knowledge, and (v) damaged fibre is shorter and weaker — directly reducing farmer income.
⚠️ Symptoms to watch for
- Direct damage: adult weevils feed on tender jute leaves and shoots (minor damage — small holes in leaves); female weevils bore small holes in jute stems with the rostrum and lay eggs inside the stem tissue. Larvae tunnel inside the jute stem, feeding on pith and vascular tissue, causing characteristic swollen galls (5-15 mm diameter) on the stem, disrupting nutrient and water transport. Damaged plants: yellowing and stunting, reduced fibre yield (20-40% reduction in severely infested crops), reduced fibre quality (shorter and weaker fibre due to disrupted vascular tissue), premature drying of plants. Crop loss: 10-25% fibre yield loss in unprotected crops; ₹50-100 crore annual loss to Indian jute industry.
🩹 Treatment
- Install light traps @ 1/ha in jute fields (adults attracted to light — monitoring and mass trapping), apply carbofuran 3G @ 10 kg/ha to soil at sowing (systemic insecticide — controls stem weevil larvae inside stems, but highly toxic to mammals and restricted use), spray monocrotophos 36 SL @ 1 ml/L on stems (systemic — reaches larvae inside stems), spray chlorpyriphos 20 EC @ 2 ml/L on stems (limited efficacy — contact action only), destroy infested plants and crop residue after harvest (removes overwintering larvae and pupae).
🌿 Organic treatments
- Apply neem cake @ 500 kg/ha to soil at sowing (repels adults and deters oviposition — also fertilises the crop), apply Beauveria bassiana @ 5 g/L as stem spray (entomopathogenic fungus — limited efficacy on larvae inside stems but kills adults), spray NSKE 5% on stems (azadirachtin-based — deters oviposition), spray Vitex negundo leaf extract 5% on stems (repels adults), use light traps @ 1/ha (adults attracted to light), collect and destroy infested plants (removes larvae and pupae), apply wood ash on stems in early morning (smallholder practice — deters oviposition), conserve natural enemies (predatory bugs, spiders — limited efficacy against larvae inside stems), practice crop rotation with non-hosts (rice, pulses — breaks weevil life cycle), destroy crop residue after harvest (removes overwintering larvae and pupae).
🧪 Chemical treatments
- Carbofuran 3G @ 10 kg/ha to soil at sowing (systemic insecticide — controls stem weevil larvae inside stems, but highly toxic to mammals and birds — restricted use in India, avoid where possible), monocrotophos 36 SL @ 1 ml/L stem spray (systemic organophosphate — reaches larvae inside stems — effective but highly hazardous — restricted use), chlorpyriphos 20 EC @ 2 ml/L stem spray (contact organophosphate — limited efficacy on larvae inside stems), phorate 10G @ 10 kg/ha to soil at sowing (systemic — controls larvae inside stems — highly toxic — restricted use). Note: Stem weevil larvae are protected inside jute stems — contact insecticides have limited efficacy. Systemic insecticides (carbofuran, monocrotophos, phorate) are effective but hazardous — use only when pest population crosses ETL and follow all safety precautions. Avoid spraying during flowering to protect pollinators. Observe withholding period before harvest.
🛡️ Prevention
- Plant jute early (mid-March to mid-April in eastern India — early planting allows plants to establish before peak stem weevil activity in July-August), use resistant jute varieties (tossa jute Corchorus olitorius varieties are generally less susceptible than white jute Corchorus capsularis — JRO-524, JRO-8432), practice crop rotation with non-hosts (rice, pulses — breaks stem weevil life cycle), destroy crop residue after harvest (burn or plough under — removes overwintering larvae and pupae), avoid continuous jute cultivation in same field (builds up stem weevil population), apply neem cake @ 500 kg/ha to soil at sowing (repels adults and deters oviposition), install light traps @ 1/ha (monitoring and mass trapping of adults), use balanced fertilization (avoid excess nitrogen which favours weevil population buildup), conserve natural enemies (predatory bugs, spiders, parasitic wasps — limited efficacy against larvae inside stems but kill adults), avoid broad-spectrum insecticides (kill natural enemies), plant trap crops (early-planted jute around field borders to attract and concentrate weevils — then destroy), implement Integrated Pest Management (IPM) with monitoring, biological control, and need-based insecticide application, harvest jute at proper maturity (120-150 DAS — over-mature crops are more susceptible to weevil damage).
🪴 Affected plants
- Jute (Corchorus capsularis — white jute, more susceptible; Corchorus olitorius — tossa jute). Not commonly reported on other plants — relatively host-specific to jute. India is the world's largest jute producer with major growing belts in West Bengal, Bihar, Assam, Odisha, and eastern Uttar Pradesh.
🦋 Natural predators
- Predatory bugs (Geocoris, Orius — feed on adults), spiders (capture adults), parasitic wasps (Eulophidae — limited efficacy on larvae inside stems). Natural enemies are limited because larvae are protected inside stems — conservation of natural enemies is still important for adult control.
🌱 Host plants
- Corchorus capsularis (white jute — more susceptible), Corchorus olitorius (tossa jute — less susceptible)
🔄 Lifecycle
- Adult female lays 30-60 eggs inside jute stems (bored with the rostrum).
- Egg incubation 4-7 days.
- Larva tunnels inside jute stem, feeding on pith and vascular tissue, over 20-30 days; larval feeding causes characteristic swollen galls (5-15 mm diameter).
- Mature larva pupates in a pupal chamber within the stem.
- Pupal stage 7-12 days.
- Adult lifespan 30-60 days (continues to feed on leaves and lay eggs).
- Total life cycle 35-50 days at 25-30°C; 4-5 overlapping generations per year in tropical India.
- Adults overwinter in crop residue and emerge in March-April to infest new jute crop.
📅 Season
- Year-round in tropical India; peaks Jul-Aug (peak monsoon — exactly when jute is in active vegetative growth and most vulnerable to weevil damage).
- Pest activity is lowest during the dry winter (Dec-Feb).
🔎 Appearance
- Adult is a small, black, pear-shaped weevil (family Apionidae) with a long slender snout (rostrum) typical of weevils; antennae clubbed and elbowed, located midway on the snout; elytra smooth with fine punctures; legs dark with paler tarsi.
- Larvae are creamy-white, legless grubs with a brown head capsule, curved body (C-shaped when disturbed), found inside jute stems.
- Pupae are creamy-white inside pupal chambers in the jute stem.
- Distinct from other weevils by small size, pear shape, and occurrence inside jute stems.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- South Asia
- Southeast Asia
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