At a glance
- Signs: Silvery or bronze streaking on leaves; tiny black fecal dots; distorted, curled new growth
- The insects: Very small (1-2mm), slender, tan or black; move fast; fly and jump
- Most effective treatment: Spinosad (Captain Jack's Dead Bug Brew); apply weekly for 6 weeks
- Catch adults: Blue sticky traps (thrips prefer blue over yellow)
- Treat soil too: Thrips pupate in the top soil layer; neem drench or diatomaceous earth
- Isolate immediately: Thrips fly and spread rapidly to other plants
What thrips are
Thrips (order Thysanoptera) are very small, slender insects, typically 1 to 2mm long, that feed by rasping plant tissue and sucking out the contents. Unlike spider mites (which are arachnids) or scale (which become stationary once settled), thrips are highly mobile: they fly, jump, and move quickly when disturbed. Both adults and nymphs feed on plant tissue, primarily on the undersides of leaves and on developing new growth.
Thrips are particularly damaging because they lay eggs inside plant tissue, where they are protected from surface sprays. This, combined with a soil-stage pupation phase, means that surface-only treatments rarely eliminate an infestation completely without sustained effort over several weeks.
How to identify thrips damage
The characteristic damage pattern is silvery or bronzy streaking on the upper leaf surface, caused by the thrips rasping open individual leaf cells and draining them. This is similar to spider mite stippling but tends to create longer streaks rather than individual dots, and appears shinier or more metallic. Close inspection of the affected areas often reveals small black specks: thrips fecal matter deposited on the leaf surface, which is a highly reliable diagnostic sign.
New growth is often most severely affected. Leaves that were forming while thrips were feeding emerge distorted, curled, or with unusual markings. If a plant consistently produces deformed new leaves, thrips are a likely cause. To confirm, hold a white piece of paper under a branch and tap the plant sharply: tiny moving specks that drop onto the paper are thrips or their nymphs.
Step 1: isolate immediately
Thrips can fly and jump from plant to plant. Move the affected plant away from all others the moment you suspect an infestation. Inspect every plant that was nearby for early signs: silvery leaf surfaces, black fecal spots, or distorted new growth. Check under leaves with a magnifying glass.
Step 2: blue sticky traps
Unlike aphids and whiteflies, which are attracted to yellow sticky traps, thrips are more strongly attracted to blue. Place blue sticky traps near the plant (or yellow traps if blue are not available; they also catch some thrips). Traps significantly reduce the adult flying population and help you monitor whether the infestation is declining as treatment progresses. Count the thrips caught each week; a consistent decline confirms the treatment is working.
Step 3: spinosad spray (most effective treatment)
Spinosad is a naturally derived insecticide from the soil bacterium Saccharopolyspora spinosa. It is highly effective against thrips at all above-ground life stages and works by disrupting the insect's nervous system. It is available as Captain Jack's Dead Bug Brew, Monterey Garden Insect Spray, and similar products.
Apply spinosad to all leaf surfaces, paying particular attention to the undersides where thrips feed and lay eggs, and to the growing tips and new growth where they concentrate. Follow the product dilution instructions. Apply every 5 to 7 days for at least 4 to 6 weeks to catch all hatching generations. Spinosad degrades relatively quickly in sunlight, so indoor application stays active longer; avoid spraying in direct sun.
Neem oil and insecticidal soap have some effect on thrips but are significantly less reliable than spinosad, particularly against the egg stage. Use spinosad as the primary treatment; neem can supplement it.
Step 4: treat the soil
Late-instar thrips nymphs drop from the plant into the top layer of soil to pupate before emerging as adults. Surface sprays on the plant leaves do not reach them during this stage. Addressing the soil is essential for breaking the full life cycle.
Options for soil treatment: apply a neem oil soil drench (mix neem oil with water and soap emulsifier, water the soil with it); top-dress the soil surface with diatomaceous earth (a powder that physically damages insects passing through it); or apply a spinosad soil drench. Any of these used consistently with the leaf treatment significantly shortens the time to full elimination.
What to expect during treatment
Thrips are one of the more persistent houseplant pests because of their multi-stage life cycle and the protection eggs receive inside plant tissue. Do not expect rapid results. Consistent weekly treatment for 4 to 6 weeks is typically required to eliminate an established infestation. During this time, continue isolating the affected plant and checking nearby plants weekly.
New growth produced during the treatment period may still emerge distorted if eggs were already laid in developing tissue before treatment began. Judge treatment success by the reduction in adult thrips on traps and the condition of the newest growth emerging after several weeks of consistent spraying.
Prevention
Thrips most commonly arrive on new plants brought indoors. Inspect any new plant carefully before bringing it home, and quarantine it separately for 2 weeks while watching for pest activity. Blue sticky traps placed near new arrivals help catch any adults quickly.
Thrips are also brought in through open windows during warm months, on cut flowers, and occasionally on clothing. Regular inspection of plants during your watering routine lets you catch infestations early, when they are much easier to treat.