Custard Apple Fruit Borer
Indarbela tetraonis (Moore)
📖 Description
Custard Apple Fruit Borer (Indarbela tetraonis), also called Fruit and Bark Borer or Arbela Borer, is an important chewing pest of custard apple across the Indian subcontinent, particularly severe in the major custard apple-growing belts of Maharashtra (Pune, Satara, Sangli, Solapur, Aurangabad, Nashik — India’s largest custard apple-producing state), Gujarat (Junagadh, Rajkot, Amreli, Bhavnagar, Surendranagar), Tamil Nadu (Theni, Dindigul, Virudhunagar, Ramanathapuram), Andhra Pradesh (Anantapur, Kurnool, Chittoor, Kadapa), Telangana (Mahabubnagar, Nalgonda), Karnataka (Ballari, Raichur, Koppal, Tumakuru) and Madhya Pradesh (Betul, Chhindwara, Hoshangabad) where India is the world’s largest producer of custard apple (over 100,000 hectares cultivated, producing over 200,000 tonnes annually — custard apple is a critical dryland fruit crop for the semi-arid regions of India, grown mostly as a rainfed crop with minimal inputs). The pest is unusual among fruit pests because (a) it is a dual pest — larvae bore both into fruits (causing direct fruit loss) and into tree trunks and main branches (causing decline and dieback of trees), (b) the larvae live inside their tunnels throughout the day and emerge only at night to feed on bark and nearby fruits, making them difficult to detect and control, (c) the webbed tunnels with frass and silken threads on the trunk are characteristic and allow easy diagnosis of trunk infestation, (d) the pest has a very long life cycle (8-12 months) — only one generation per year — meaning that a single missed season of management leads to multi-year infestation buildup, (e) the pest has a wide host range including pomegranate, mango, citrus, guava, ber, aonla, litchi and jamun allowing populations to persist between custard apple crops via other fruit trees, and (f) the pest is most severe in neglected orchards with inadequate pruning and orchard sanitation. IPM with light trap monitoring (most critical for early detection of adult activity), mechanical cleaning of webbed tunnels with a hooked wire (most effective control for trunk borers), biological control (Bt on young larvae before they enter fruit/stem, Beauveria bassiana as trunk paste), neem-based trunk pastes to deter oviposition, fruit bagging in small orchards, and need-based insecticide rotation (apply as full cover spray on fruits and trunk) provides effective and sustainable control. The pest is a particular concern for custard apple growers because of the long life cycle (8-12 months) and the dual fruit/trunk infestation mode — a single missed season of management can lead to multi-year infestation buildup that is difficult and expensive to control. The pest is most severe in neglected orchards and in dryland plantations where regular monitoring and orchard sanitation are difficult.
⚠️ Symptoms to watch for
- Webbed tunnels with frass on tree trunks and main branches (characteristic bark borer symptom), larval entry holes on fruit surface (1-3 mm diameter) with frass and silk around the opening, fruits with internal feeding (larvae consume the fleshy syncarp and seeds), premature fruit drop and shrivelling, secondary fungal infection (especially Colletotrichum, Botryodiplodia) through feeding wounds leading to fruit rot, decline and dieback of branches in severe trunk infestations, yield loss 20-40% in custard apple, 60-100% loss in late-stage outbreak with severe trunk damage
🩹 Treatment
- Install light traps @ 1/ha for monitoring adult moth activity, clean out webbed tunnels with a hooked wire and kill larvae inside, spray neem oil 1% on tree trunks to deter oviposition, spray Bt (Bacillus thuringiensis) @ 1 kg/ha on young larvae before they enter fruit/stem, use need-based insecticide at first sign of fruit infestation, bag fruits with paper or polythene bags to prevent oviposition (effective in small orchards)
🌿 Organic treatments
- Clean out webbed tunnels with a hooked wire and kill larvae inside (mechanical control — most effective for trunk borers), apply Bacillus thuringiensis (Bt) @ 1 kg/ha on young larvae before they enter fruit/stem, spray neem oil 1% + 5 g/L soap on tree trunks to deter oviposition, apply Beauveria bassiana @ 5 g/L as trunk spray or paste, spray NSKE 5%, apply Metarhizium anisopliae @ 5 g/L, apply azadirachtin 10000 ppm @ 2 ml/L, bag fruits with paper or polythene bags to prevent oviposition, paste tree trunks with cow dung + clay + neem oil mixture to deter oviposition
🧪 Chemical treatments
- Chlorantraniliprole 18.5 SC @ 0.3 ml/L, Emamectin benzoate 5 SG @ 0.3 g/L, Spinosad 45 SC @ 0.2 ml/L, Lambda-cyhalothrin 5 EC @ 0.5 ml/L, Profenofos 50 EC @ 1 ml/L — apply as full cover spray on fruits and trunk at first sign of infestation. Always rotate modes of action to slow resistance development. Note: avoid spraying insecticides close to fruit harvest to avoid residue issues
🛡️ Prevention
- Inspect orchards weekly for adult moth activity (use light traps @ 1/ha for monitoring), inspect tree trunks and main branches for webbed tunnels during pruning, clean out and destroy webbed tunnels during dormant season, prune and destroy heavily infested branches, destroy fallen and infested fruits, maintain proper tree spacing (5 m x 5 m) to reduce humidity buildup, balanced fertilization (avoid excess nitrogen which favours larval development), avoid mechanical injury to tree trunks (which attracts ovipositing females), paste tree trunks with cow dung + clay mixture to deter oviposition, plant resistant varieties where available, use fruit bagging in small orchards
🪴 Affected plants
- Custard Apple (Sitaphal), Pomegranate, Mango, Citrus, Guava, Ber, Aonla (Indian Gooseberry), Litchi, Jamun, Many Other Fruit Trees and Ornamentals
🦋 Natural predators
- Predatory Birds (Woodpecker, Drongo, Oriole), Predatory Beetles ( Clerid, Staphylinid), Parasitoid Wasps (Bracon, Ichneumon), Spiders, Ants (against young larvae), Predatory Bugs (Praying Mantis)
🌱 Host plants
- Annona squamosa, Punica granatum, Mangifera indica, Citrus spp., Psidium guajava, Ziziphus mauritiana, Phyllanthus emblica, Litchi chinensis, Syzygium cumini
🔄 Lifecycle
- Female lays 300-800 eggs in clusters of 30-100 in bark crevices or in the crevices between fused carpels of the fruit.
- Eggs hatch in 8-12 days.
- Larvae bore into the fruit (causing direct fruit damage) or into the trunk/branches (causing decline) and feed internally for 8-12 months.
- Pupation occurs inside the tunnel or in a silken cocoon at the tunnel entrance; pupal stage 20-30 days.
- Adult lifespan 7-15 days; female lays 300-800 eggs.
- Total life cycle 8-12 months; 1 generation per year in India.
📅 Season
- Year-round in tropical India; adult emergence peaks Apr-Jun (pre-monsoon) and Sep-Nov; fruit damage peaks Jul-Nov (main fruiting season)
🔎 Appearance
- Mature larva is a stout, brownish caterpillar with a dark brown head capsule and pale brown body marked with darker dorsal and lateral stripes; body covered with sparse short setae; prolegs well developed.
- Larvae are rarely seen as they feed inside the fleshy syncarps of custard apple fruits and inside woody stems and branches where they create characteristic webbed tunnels with frass and silken threads.
- Adults are large pale greyish-white moths (50-60 mm wingspan) with black dots and zigzag markings on the forewings — they are nocturnal and rest on tree trunks during the day.
- Eggs are laid in clusters of 30-100 in bark crevices or in the crevices between fused carpels of the fruit.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Slow
🗺️ Geographic regions
- Indian Subcontinent
- South Asia
- Southeast Asia
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