Predatory Thrips
Scolothrips sexmaculatus
📖 Description
Scolothrips sexmaculatus, the six-spotted thrips, is one of the most important specialised predators of spider mites in Indian agriculture and a key natural enemy of the two-spotted spider mite (Tetranychus urticae) and red spider mite (Tetranychus cinnabarinus) in cotton, vegetables, and ornamentals. The species has 8–12 overlapping generations per year in tropical Indian conditions. Both adults and nymphs are voracious predators, each consuming 30–60 mite eggs or 10–20 mobile mites per day. The species is highly mobile and can locate mite colonies from a distance of several metres using volatile kairomones released by mite-damaged plants. S. sexmaculatus is mass-reared by several Indian biocontrol laboratories (NBAIR Bengaluru, IIHR Bengaluru, UAS Bengaluru) and released in polyhouse cucumber and rose crops for mite management. Estimated value of biological control services provided by S. sexmaculatus and related predatory thrips (Franklinothrips, Aeolothrips) in Indian agriculture exceeds ₹1,500 crore per year — primarily through avoided miticide costs and reduced mite-related yield losses.
⚠️ Symptoms to watch for
- No plant damage — this is a beneficial predator.
- Visible presence of six-spotted thrips on leaves previously infested with spider mites, gradual reduction in mite colonies, and absence of webbing on previously infested leaves.
- The species is a key natural enemy of the two-spotted spider mite (Tetranychus urticae) and red spider mite (Tetranychus cinnabarinus) in Indian cotton and vegetable crops.
🩹 Treatment
- No treatment needed — this is a beneficial insect.
- Conserve by avoiding broad-spectrum insecticides during its peak activity (June–October).
- If pest mites need control, use selective miticides (bifenazate, etoxazole, acequinocyl) that are safe to predatory thrips.
- Provide flowering plants (marigold, mustard, buckwheat) as pollen and nectar sources to support adult longevity and fecundity.
- Avoid applying sulphur, abamectin, or chlorfenapyr — these are toxic to predatory thrips.
🌿 Organic treatments
- Conservation biological control: avoid broad-spectrum insecticides
- provide flowering companion plants (marigold, mustard, buckwheat) as pollen/nectar sources
- maintain refugia (hedgerows, groundcovers) for overwintering
- release commercially reared Scolothrips sexmaculatus at 5–10 thrips/m² in polyhouse crops where natural colonisation is insufficient.
🧪 Chemical treatments
- No treatment needed — beneficial insect.
- If pest mites need control, use selective miticides safe to predatory thrips: bifenazate 24 SC @ 0.5 ml/L
- etoxazole 10 SC @ 0.5 ml/L
- acequinocyl 15 SC @ 1.0 ml/L.
- Avoid: sulphur, abamectin, chlorfenapyr, pyrethroids — all toxic to predatory thrips.
🛡️ Prevention
- No prevention needed — this is a beneficial predator that should be conserved.
- To attract and sustain populations: maintain diverse groundcover in crop fields to provide alternative prey and shelter
- provide flowering companion plants (marigold, mustard, buckwheat) as pollen/nectar sources
- avoid broad-spectrum insecticides during its peak activity (June–October)
- use selective pest-control tools (Bt, NPV, neem, pymetrozine) that are safe to predatory thrips
- maintain refugia (hedgerows, field margins) for overwintering.
🪴 Affected plants
- Polyphagous predator of spider mites (Tetranychus spp.)
- broad mites (Polyphagotarsonemus latus)
- thrips larvae
- and other small arthropods on cotton
- vegetables
- fruit crops
- ornamentals
- and field crops throughout India.
🦋 Natural predators
- As a predator itself, S. sexmaculatus has few significant natural enemies.
- Anthocorid bugs (Orius spp.) and predatory mites (Amblyseius spp.) occasionally prey on early instar nymphs
- entomopathogenic fungi (Beauveria bassiana, Lecanicillium lecanii) can cause mortality under humid conditions.
🌱 Host plants
- Polyphagous predator — does not feed on plants.
- Found on cotton, vegetables (tomato, brinjal, cucumber, okra), fruit crops (citrus, mango, grape), ornamentals (rose, chrysanthemum), and field crops where spider mites and other small arthropods occur.
🔄 Lifecycle
- Eggs laid in leaf tissue hatch in 4–6 days; nymphs feed on mites for 7–10 days (2 instars); two non-feeding pupal instars in leaf litter or soil for 3–5 days; adult lifespan 20–30 days.
- Total lifecycle 14–21 days at 28°C; 8–12 overlapping generations per year in tropical Indian conditions.
📅 Season
- Active year-round in tropical Indian conditions; populations peak during the warm dry months (April–June and October–November) when spider mite populations are highest.
🔎 Appearance
- Adult is a small, slender, dark brown to black thrips with three pairs of distinctive dark spots on the otherwise pale forewings — giving the species its common name 'six-spotted thrips'.
- The body is elongate and somewhat flattened; legs are pale yellow with dark femora.
- Nymphs are pale yellow to creamy-white with red eyes.
- Unlike pest thrips, predatory thrips have stout, sharply pointed mouthparts for piercing prey, and they move actively and rapidly across leaf surfaces in search of mite colonies.
💥 Damage level
- Beneficial
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent (pan-India in cotton, vegetable, fruit crop tracts)
- pantropical and warm-temperate worldwide.
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