Thrips tabaci
6
Damage Signs
4
Organic Methods
3
Chemical Options
5
ID Tips
2
FAQs
6
Crops Affected
Updated February 2026
Vede Onion Thrips sulle sue piante?
Carichi una foto per l'identificazione istantanea con metodi di controllo biologici e chimici.
Overview
The most damaging pest of onion, garlic, and leek worldwide. Thrips tabaci feeds by rasping leaf tissue and sucking up cell contents, causing silvery white patches that reduce photosynthesis and create wounds for disease entry (particularly purple blotch). Heavy infestations can reduce onion bulb size by 30-50%. Thrips also transmit Iris yellow spot virus (IYSV).
Field Guide
Adults are tiny (1-1.5 mm), slender, pale yellow to light brown insects with fringed wings. Nymphs are wingless, smaller, and pale yellow. Both stages feed deep in leaf axils and between tightly packed leaves, making them difficult to reach with sprays. Use a hand lens to see them clearly.
Peel back leaf axils (where leaves join the bulb neck) — thrips hide deep inside where sprays cannot easily reach
Tap leaves over a white piece of paper — thrips fall and are visible as tiny moving specks
Silvery-white feeding damage on onion leaves is highly characteristic of thrips
Use a 10× hand lens to see the fringed wings and slender body shape
Blue sticky traps catch thrips preferentially over yellow traps
Scouting Guide
Silvery white patches and streaks on leaves (feeding damage)
Leaves appear whitish or bleached from heavy feeding
Tiny black fecal spots on leaf surfaces near feeding sites
Distorted and curled leaf tips
Increased purple blotch severity due to feeding wounds providing disease entry
Reduced bulb size and delayed maturity
Biology
Egg inserted into leaf tissue (5-10 days) → 2 nymphal instars feeding on leaves (8-12 days) → pre-pupa and pupa in soil (3-5 days) → adult (14-30 days). Generation time 2-4 weeks. Populations build rapidly in hot, dry weather.
Pest Management
Spinosad (Tracer 480SC)
Apply spinosad at 0.5 ml/L every 7-10 days targeting nymphs in leaf axils. Organic-approved spinosad formulations are available.
Neem oil
Apply neem oil at 3-5 ml/L with spreader-sticker. Must contact thrips — thorough coverage of inner leaves is critical.
Blue sticky traps
Install blue (not yellow) sticky traps at canopy height — thrips are preferentially attracted to blue. Useful for monitoring rather than control.
Overhead irrigation
Brief overhead irrigation during hot dry periods physically dislodges thrips and increases humidity, slowing reproduction. Balance against increased foliar disease risk.
Use as last resort. Follow label instructions. Wear protective equipment.
Spinetoram (Radiant 120SC)
Apply at 0.5 ml/L every 7-10 days. More persistent than spinosad, excellent thrips activity.
Fipronil (Regent 200SC)
Apply at 0.5 ml/L as soil drench at transplanting for systemic protection during early establishment.
Cyantraniliprole (Benevia 10OD)
Apply at 1 ml/L. Novel mode of action effective against thrips populations resistant to older chemistries.
Host Range
Onion Thrips can attack 6 crop species.
Common Questions
Onion leaves are smooth and waxy, causing sprays to run off. Thrips hide deep in the leaf axils (the tight spaces where leaves join the neck), where spray droplets cannot penetrate. Using a spreader-sticker surfactant with insecticide, and applying with high-volume directed sprays, improves coverage. Some growers add 0.1% non-ionic surfactant to all thrips sprays.
Yes, dramatically. Thrips feeding creates thousands of tiny wounds in the leaf epidermis. These wounds serve as entry points for Alternaria porri (purple blotch) and other foliar pathogens. Research shows 3-5× more purple blotch on thrips-damaged leaves versus undamaged leaves. Managing thrips is therefore also essential for disease management.
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