Ramie Shoot Borer
Sphenarches caffer
📖 Description
Sphenarches caffer, the Ramie Shoot Borer, is a pterophorid (plume) moth pest of ramie (Boehmeria nivea), one of the strongest natural bast fibres known. Ramie is a minor but commercially important fibre crop in India, grown primarily in Assam, West Bengal, and the north-eastern hill states, with smaller plantations in Maharashtra and Tamil Nadu. The fibre is valued for its exceptional tensile strength, lustre, and resistance to microbial degradation, and is used in high-value textile blends, fishing nets, and industrial sewing threads. Ramie is a perennial crop harvested 3–4 times per year by cutting the stems at ground level and allowing regrowth from the crown — this harvesting system means the crop is in continuous tender regrowth, providing year-round food supply for shoot-boring pests. The shoot borer is most damaging in the first 30 days after each cutting, when the new shoots are tender and the larva can kill the apical meristem. Damage forces lateral bud break, producing multiple weak stems that yield shorter, coarser fibre unsuitable for premium textile use. IPM packages developed by ICAR-CRIJAF for ramie emphasise weekly shoot pruning during the post-cutting regrowth period, balanced nutrition, and Btk applications as the core management tactics. The pest has 5–6 overlapping generations per year, with peak activity during the warm humid months of April–October. Population crashes during the cool dry winter (December–February) when ramie growth slows.
⚠️ Symptoms to watch for
- Bore-hole at the base of the tender apical shoot with frass pushed out
- wilting and drooping of the central shoot ('dead-heart' symptom)
- lateral bud break below the damage point producing multiple weak shoots
- stunted main stem and reduced fibre yield.
- In ramie plantations in Assam, West Bengal, and the north-eastern hill states, heavy infestation can reduce fibre yield by 15–25 % by stunting the main stem and reducing the number of harvestable cuttings per year.
🩹 Treatment
- Cultural: prune off and destroy infested shoots below the bore-hole at weekly intervals.
- Mechanical: install light traps at 2/ha to monitor adult activity.
- Biological: spray Bacillus thuringiensis var. kurstaki (Btk) at 1 g/L on tender shoot growth at 15-day intervals
- release Trichogramma chilonis at 50,000/ha for egg parasitism.
- Chemical: spray quinalphos 25 EC @ 1.5 ml/L or lambda-cyhalothrin 5 EC @ 0.5 ml/L directed at the tender shoot growth, repeated at 15-day intervals during peak infestation.
🌿 Organic treatments
- Spray neem oil (Azadirachta indica) at 3 % emulsion on tender shoot growth at 15-day intervals
- apply Beauveria bassiana at 5 g/L on the shoot tip
- install light traps at 2/ha for adult monitoring
- prune and burn infested shoots weekly.
🧪 Chemical treatments
- Quinalphos 25 EC @ 1.5 ml/L, Lambda-cyhalothrin 5 EC @ 0.5 ml/L, Emamectin benzoate 5 SG @ 0.4 g/L.
- Direct spray at tender shoot growth.
- Pre-harvest interval 21 days for quinalphos, 7 days for pyrethroids.
🛡️ Prevention
- Prune off and destroy infested shoots weekly during the period of tender regrowth after each cutting
- avoid excessive nitrogen fertilisation that promotes continuous tender flushes
- maintain plantation sanitation — remove and burn pruned material
- install light traps at 2/ha to monitor adult activity
- remove wild Urticaceae hosts around plantation margins
- in new plantations, plant resistant or tolerant varieties where available.
🪴 Affected plants
- Ramie (Boehmeria nivea) — primary host
- also reported on other Urticaceae and occasionally on hemp (Cannabis sativa).
🦋 Natural predators
- Trichogramma chilonis (egg parasitoid — 20–30 % field parasitism in unsprayed plantations)
- Apanteles spp. (larval braconid parasitoids)
- predatory pentatomid bugs (Eocanthecona furcellata)
- lacewing larvae (Chrysoperla zastrowi)
- and spiders.
🌱 Host plants
- Boehmeria nivea (ramie — primary)
- other Urticaceae
- and occasionally Cannabis sativa (hemp).
🔄 Lifecycle
- Adult female lays 60–150 eggs singly on tender leaves and shoot tips.
- Egg stage 4–6 days.
- Larva passes through five instars over 14–20 days, boring into the shoot.
- Pupation occurs on the leaf surface or stem, attached by a silken pad; pupal stage 7–10 days.
- Adult longevity 7–12 days.
- Total lifecycle 28–40 days.
- Five to six overlapping generations per year.
📅 Season
- Active April–October across the Indian ramie belt; peak infestation May–August during the warm humid months when regrowth after cutting is most rapid.
- Population crashes during the cool dry winter.
🔎 Appearance
- Adult is a small brownish-grey pterophorid (plume moth) — the forewings are divided into two plumes and the hindwings into three, giving the resting moth a distinctive T-shape with wings held at right angles to the body.
- Body is slender and long-legged.
- Larva is a greenish-yellow caterpillar with a dark head capsule and sparse pale setae; the larva bores into the tender apical shoot of ramie.
- Pupa is dark brown, attached to the leaf surface or stem by a silken pad.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Medium
🗺️ Geographic regions
- Indian Subcontinent (Assam, West Bengal, north-eastern hill states)
- South Asia
- parts of Southeast Asia and Africa.
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