Thrips on calathea
What's Happening
Thrips (Thysanoptera) are minute sap-sucking insects that infest Calathea by hiding in dense foliage and pupating in soil, enabling rapid population explosions. Unlike spider mites that prefer dry conditions, thrips thrive in Calathea's preferred 60-70% humidity range. Infestations often begin after periods of plant stress when defenses are compromised—recently 'happy and healthy' plants suddenly show damage as thrips exploit the high-humidity microclimate. Damage appears as silver stippling, distorted new growth, and black frass (excrement) specks on leaf undersides. Pupae in soil render foliar-only treatments ineffective.
How to Fix It
- 1
Isolate infested Calathea immediately; thrips spread via air currents and contact with nearby plants
- 2
Rinse all foliage thoroughly under strong water stream, focusing on undersides, to dislodge adults, nymphs, and frass
- 3
Prepare bucket with lukewarm water, insecticidal soap, and neem oil; dunk foliage for 10-15 minutes (wrap soil in plastic to protect roots)
- 4
Apply thrips-specific biocide like spinosad or pyrethrin-based treatment, ensuring coverage of undersides and crown
- 5
Repeat treatments every 5-7 days for 3 weeks minimum to target multiple life cycles—eggs, larvae, pupae, adults
- 6
Deploy yellow sticky traps continuously for 4+ weeks to monitor and capture emerging adults from soil pupae
- 7
Prune heavily damaged leaves to reduce hiding spots and encourage new healthy growth; Calathea's rhizomatous structure supports robust regrowth
What You'll Need
How to Prevent It
Quarantine new plants 2-4 weeks with weekly inspections focusing on leaf undersides and new growth. Deploy yellow sticky traps near plants to capture adult thrips before egg-laying begins. Ensure good airflow between plants—thrips spread via air currents and physical contact. Inspect during active growth phases when new tissue is most vulnerable. Maintain consistent care to prevent stress-induced vulnerability.