Cashew Apple Sucker (Cashew Thrips)
Scirtothrips dorsalis (Cashew Race)
📖 Description
Scirtothrips dorsalis — the Cashew Apple Sucker or Cashew Thrips — is the most damaging insect pest of cashew inflorescences in India, with economic significance centred on the cashew belts of Maharashtra (Ratnagiri, Sindhudurg — Konkan coast), Goa, Karnataka (Uttara Kannada, Dakshina Kannada), Kerala (Kollam, Thiruvananthapuram), Andhra Pradesh (Visakhapatnam, East Godavari), Odisha (Gajapati, Rayagada), and West Bengal (Purba Medinipur). India is the world’s largest cashew producer (~750,000 tonnes of raw cashew nuts from ~1 million ha), with cashew being a major export crop valued at ₹4,000–6,000 crore annually. The pest is part of the Scirtothrips dorsalis species complex — a group of morphologically indistinguishable but biologically distinct races that preferentially colonise different host plants (chilli race, mango race, cotton race, cashew race). The cashew race is native to India — it was first reported as a major pest of Indian cashew in the 1980s and has since become established as the most damaging thrips pest of Indian cashew, particularly during the flowering season (November–March). The pest’s biology makes it particularly damaging: (1) eggs are concealed inside plant tissue — protected from contact insecticides; (2) pupation occurs in soil or leaf litter — protected from foliar insecticides; (3) parthenogenetic reproduction — a single female can found a new population; (4) rapid reproduction — females lay 60–100 eggs and complete a generation in 14–18 days; (5) wide host range (over 100 plant species) — survives on alternative hosts (mango, chilli, cotton, tea, grape) between cashew flowering seasons; and (6) high insecticide resistance — the cashew race has documented resistance to organophosphates, pyrethroids, and even neonicotinoids in Maharashtra Konkan. The economic impact is severe: heavy infestations can cause 50–80% flower drop, directly reducing nut yield by 30–60% and apple quality by 40–70%. With raw cashew nuts valued at ₹80–120 per kg and cashew apples (used for Feni liquor in Goa) at ₹15–25 per kg, even moderate infestations cause disproportionate economic loss — for a typical Konkan cashew grower cultivating 4 ha (yield 800–1,200 kg/ha), a severe S. dorsalis infestation can wipe out ₹80,000–250,000 of annual income. Management is best achieved through IPM combining orchard sanitation (pruning and destroying curled leaves during the dormant season), tolerant varieties (Vengurla-4, Vengurla-7 — DCRS-released varieties), blue sticky trap monitoring, NSKE 5% or azadirachtin foliar sprays during peak oviposition, biological control (Amblyseius swirskii predatory mite releases), threshold-based spinetoram application (preserving susceptibility), conservation of natural enemies and pollinators (avoiding broad-spectrum insecticides during bloom), windbreaks, and alternative host weed management. The Directorate of Cashew Research (ICAR-DCRS, Puttur, Karnataka) is the primary research institution for cashew IPM in India.
⚠️ Symptoms to watch for
- Adults and nymphs rasp the surface of tender cashew leaves, inflorescences, and developing apples/nuts with their single mandibular stylet, sucking up the exuded cell sap. Feeding on tender leaves causes characteristic leaf curling, distortion, and a 'scorched' silvery-brown appearance — affected leaves remain small, distorted, and fail to expand normally. Feeding on inflorescences causes flower drop, reduced fruit set, and 'bunched' malformed panicles — heavy infestation can cause 50–80% flower drop, directly reducing nut yield. Feeding on developing apples and nuts causes surface scarring, browning, and reduced apple/nut size — apples become unmarketable as fresh fruit (the cashew apple is consumed as fresh fruit and used to produce Feni liquor in Goa). The pest also vectors Cashew Yellow Net Virus (CYNV) — a less common but serious disease. Heavy infestations can reduce nut yield by 30–60% and apple quality by 40–70%.
🩹 Treatment
- Apply spinetoram 11.7 SC at 0.5 ml/L — most effective thrips insecticide; translaminar activity. Apply cyantraniliprole 10 OD at 1.5 ml/L — systemic diamide. Apply imidacloprid 17.8 SL at 0.3 ml/L — systemic; effective against nymphs. Apply acetamiprid 20 SP at 0.4 g/L — systemic; less bee-toxic. Apply fipronil 5 SC at 1 ml/L — contact + systemic; avoid during bloom (toxic to bees). Apply diafenthiuron 50 WP at 1 g/L — mitochondrial ATP synthase inhibitor. Apply azadirachtin 1% at 2 ml/L — antifeedant. Use blue sticky traps at 8–12 per ha to monitor adult thrips migration. Rotate insecticide mode-of-action (IRAC groups) to prevent resistance — S. dorsalis has documented resistance to organophosphates and pyrethroids in Indian cashew belts.
🌿 Organic treatments
- Spinosad 45 SC — 0.3 ml/L; derived from Saccharopolyspora spinosa; effective against adults and larvae; OMRI-listed. Azadirachtin 1% (NeemAzal) — 2 ml/L; antifeedant and growth disruptor. Lecanicillium lecanii (1×10⁹ CFU/g) at 5 g/L — entomopathogenic fungus specific to thrips; effective under humid microclimate. Beauveria bassiana (1×10⁹ CFU/g) at 5 g/L — entomopathogenic fungus. Neem seed kernel extract (NSKE) 5% — repels ovipositing adults. Blue sticky traps at 8–12 per ha — mass-trap adults; blue is more attractive to thrips than yellow. Reflective mulch (silver-coloured polythene on orchard floor) — repels thrips from lower leaves. Release Amblyseius swirskii predatory mites at 50,000/ha — most effective biological control for thrips; commercially reared by NBAIR Bangalore. Conserve natural enemies by avoiding broad-spectrum insecticides during the bloom period.
🧪 Chemical treatments
- Spinetoram 11.7 SC (Radiant) — 0.5 ml/L; nicotinic acetylcholine receptor allosteric activator; translaminar; 7-day PHI. Cyantraniliprole 10 OD (Benevia) — 1.5 ml/L; anthranilic diamide; systemic; long residual (14–21 days). Imidacloprid 17.8 SL (Confidor) — 0.3 ml/L; neonicotinoid; systemic; effective against nymphs. Acetamiprid 20 SP (Mospilan) — 0.4 g/L; neonicotinoid; systemic; less bee-toxic than imidacloprid. Fipronil 5 SC — 1 ml/L; GABA-gated chloride channel blocker; TOXIC TO BEES — avoid during bloom. Diafenthiuron 50 WP (Polo) — 1 g/L; mitochondrial ATP synthase inhibitor. Abamectin 1.9 EC (Vertimec) — 0.5 ml/L; glutamate-gated chloride channel activator; translaminar. Avoid organophosphates (chlorpyrifos, quinalphos, monocrotophos) — restricted in many Indian states and banned under the Cashew Board of India's IPM guidelines; rotate IRAC groups strictly to preserve susceptibility.
🛡️ Prevention
- Practise regular orchard sanitation — prune and destroy all curled, distorted leaves during the dormant season (September–October) before adults emerge from overwintering sites. Maintain orchard hygiene — remove cashew crop debris, fallen leaves, and weed growth under the canopy (thrips overwinter on weed hosts between cashew flowering seasons). Use blue sticky traps at 8–12 per ha from panicle emergence (November–December) to monitor adult thrips density. Plant tolerant cashew varieties — Vengurla-4, Vengurla-7, Ullal-3 (DCRS-released varieties with reduced thrips susceptibility). Release Amblyseius swirskii predatory mites preventively at 50,000/ha during the vegetative flush — most effective biological control for thrips. Apply NSKE 5% as a foliar spray on cashew terminals during peak oviposition (November–December in Maharashtra Konkan). Conserve natural enemies by avoiding broad-spectrum insecticides during the bloom period (January–March) — pollinators (bees, flies) are critical for cashew fruit set. Plant windbreaks (Gliricidia, Casuarina) around cashew orchards — thrips are weak fliers and windbreaks reduce migration. Manage alternative host weeds (Mangifera, Capsicum volunteers) within and around orchards — these maintain thrips populations between cashew flowering seasons. Maintain 10 m × 10 m spacing between cashew trees — improves ventilation and reduces thrips build-up. Apply threshold-based insecticide sprays (5 thrips per panicle) rather than calendar sprays — preserves natural enemies and pollinators.
🪴 Affected plants
- Cashew (Anacardium occidentale — primary host, attacks tender leaves, inflorescences, and developing apples/nuts). Also on mango (Mangifera indica), chilli (Capsicum annuum), cotton (Gossypium hirsutum), tea (Camellia sinensis), grape (Vitis vinifera), and over 100 other host plants — the cashew race preferentially colonises cashew but can survive on alternative hosts between cashew flowering seasons. In India, the pest is most damaging in cashew belts of Maharashtra (Ratnagiri, Sindhudurg), Goa, Karnataka (Uttara Kannada, Dakshina Kannada), Kerala (Kollam, Thiruvananthapuram), Andhra Pradesh (Visakhapatnam, East Godavari), Odisha (Gajapati, Rayagada), and West Bengal (Purba Medinipur).
🦋 Natural predators
- Amblyseius swirskii (predatory mite — Phytoseiidae; the most effective biological control agent for thrips; commercially reared by NBAIR Bangalore; release rate 50,000/ha). Amblyseius cucumeris (predatory mite — Phytoseiidae). Orius insidiosus (minute pirate bug — predatory anthocorid; attacks all thrips stages). Orius laevigatus (minute pirate bug — European species used in Indian orchards). Coccinella septempunctata (7-spot ladybird — predator of nymphs). Chrysoperla zastrowi sillemi (green lacewing — predator of nymphs). Predatory thrips (Aeolothrips intermedius). Entomopathogenic fungi (Lecanicillium lecanii, Beauveria bassiana — effective under humid microclimate). Spiders (Thomisidae — crab spiders; Salticidae — jumping spiders). Predatory ants (Oecophylla smaragdina — weaver ant; effective predator on cashew in Kerala, Karnataka). Natural enemies are most effective in unsprayed cashew orchards and in orchards with intercropped cover crops (Pueraria, Centrosema) that provide habitat for natural enemies.
🌱 Host plants
- Cashew (Anacardium occidentale — primary host, attacks tender leaves, inflorescences, and developing apples/nuts). Also on mango (Mangifera indica), chilli (Capsicum annuum), cotton (Gossypium hirsutum), tea (Camellia sinensis), grape (Vitis vinifera), strawberry (Fragaria × ananassa), and over 100 other host plants. The cashew race preferentially colonises cashew but can survive on alternative hosts between cashew flowering seasons.
🔄 Lifecycle
- Egg → Nymph (2 instars) → Pre-pupa → Pupa (in soil) → Adult.
- Females lay 60–100 eggs singly inside plant tissue (tender leaves, inflorescences, developing apples) — eggs are concealed and not visible.
- Eggs hatch in 4–6 days.
- Nymphs feed on plant surface for 6–9 days, moulting twice.
- Pre-pupal and pupal stages occur in soil or leaf litter, lasting 2–4 days — pupae do not feed.
- Adults live 20–30 days; females begin oviposition 2–3 days after emergence.
- Parthenogenetic reproduction (males rare in some populations).
- Total cycle 14–18 days at 28 °C; 12–18 overlapping generations per year in Indian cashew-growing belts, with peak activity during the flowering season (November–March).
- Pest survives off-season (June–September) on alternative hosts (mango, chilli, cotton, tea, grape) and on cashew volunteers.
📅 Season
- Peak activity November–March (cashew flowering and fruiting season in Maharashtra Konkan, Goa, Karnataka, Kerala — southwest monsoon retreats and dry weather returns, ideal for thrips reproduction).
- Lower activity April–May (hot dry summer — adult activity reduced but populations persist).
- No activity June–September (southwest monsoon — heavy rain suppresses thrips populations; pest survives on alternative hosts and cashew volunteers).
- Secondary peak October–November (early post-monsoon — adult emergence from soil-borne pupae with first dry weather; attacks tender post-monsoon vegetative flush).
🔎 Appearance
- Minute, slender, yellowish-orange thrips 0.8–1.2 mm long with feathery fringed wings.
- Body is pale yellow to orange with darker brown bands on the abdominal tergites — the species name 'dorsalis' refers to these dark dorsal bands.
- Antennae are 7-segmented.
- The cashew race is morphologically indistinguishable from other S.
- dorsalis races (chilli race, mango race, cotton race) but differs in host preference and pesticide resistance profile.
- Nymphs are smaller, paler, wingless.
- Eggs are minute (0.2 mm), kidney-shaped, inserted into plant tissue and invisible to the naked eye.
- The species is parthenogenetic in some populations (males rare).
💥 Damage level
- Severe
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- South Asia
- Southeast Asia
- East Asia
- Africa
- Australia
- Pacific Islands. In India: Maharashtra (Ratnagiri
- Sindhudurg
- Raigad — Konkan coast)
- Goa (North Goa
- South Goa)
- Karnataka (Uttara Kannada
- Udupi
- Dakshina Kannada
- Kodagu)
- Kerala (Kollam
- Thiruvananthapuram
- Kozhikode
- Kasaragod)
- Andhra Pradesh (Visakhapatnam
- East Godavari
- Srikakulam)
- Odisha (Gajapati
- Rayagada
- Koraput)
- West Bengal (Purba Medinipur
- South 24 Parganas)
- Tamil Nadu (Cuddalore
- Villupuram)
- Tripura
- Meghalaya
- Mizoram. Pest is native to South Asia — first reported as a major pest of Indian cashew in the 1980s; now established in all major cashew-growing belts.
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