Key takeaways
- 4,500+ species in order Thysanoptera — tiny, fringed-wing insects that scrape and suck cell contents from plant tissues.
- Damage signature: silvery scarring, distorted foliage, aborted fruit, and tiny black fecal specks on leaf undersides.
- Thrips transmit serious plant viruses — INSV (impatiens necrotic spot virus) and TSWV (tomato spotted wilt virus) are the worst offenders.
- Lifecycle includes soil-dwelling pupal stages for most species — meaning soil predators like Stratiolaelaps are part of the solution, not just foliar predators.
- Preventive go-to controls: Amblyseius (Neoseiulus) cucumeris, Stratiolaelaps scimitus in the media, Orius insidiosus for outbreaks, and blue or yellow sticky traps for monitoring.
Thrips are tiny insects of the order Thysanoptera — over 4,500 species, many of which pose major risks to greenhouse and floral crops. They feed by scraping plant cells, leave silvery scars, and transmit viruses that can destroy a crop independent of feeding damage alone.
Introduction
Thrips pests are tiny insects from the order Thysanoptera, posing significant risks to growers worldwide. With over 4,500 species, these insects frequently invade greenhouses and indoor plants — especially on floral crops. Thrips cause extensive plant damage and transmit serious diseases, making their management vital.
Why Thrips Are Problematic
Thrips enter growing environments through several routes. They often hide year-round within greenhouse structures or hitch rides on new plants brought in from outside. Their ability to fly long distances on fringed wings further complicates management — emphasizing the importance of early detection and immediate control.
Damage Caused by Thrips
Female thrips reproduce rapidly, embedding eggs inside plant tissues with a saw-like ovipositor. Although the act of egg-laying itself doesn’t cause major harm, thrips do their primary damage through feeding: scraping plant cells and sucking out sap. This leaves silvery scars and distorted patterns on leaves.
Thrips also transmit harmful plant viruses, including impatiens necrotic spot virus (INSV) and tomato spotted wilt virus (TSWV). Once a crop is infected, no biocontrol can reverse the virus — the only defense is to keep thrips populations below the transmission threshold from the start.
Life Cycle and Habits
The lifecycle of thrips pests is rapid, especially in warm conditions — as little as 14 days from egg to adult. In cooler weather, the lifecycle extends to a month. Thrips spend their larval stages deeply embedded in flowers or buds, complicating chemical treatments because the larvae are physically shielded by plant tissue.
For most thrips species, the prepupal and pupal stages take place in the soil or growing media. The larva drops from the plant to pupate underground, then emerges as an adult to fly back up and feed. This is why a full thrips program treats both foliage and soil.
Effective Scouting
Regular monitoring is vital for the early detection of thrips. Growers typically use yellow or blue sticky traps — blue tends to be more thrips-selective when you’re running other biocontrols that yellow would also catch. Direct plant inspections, plus gentle shaking or blowing into flowers, help reveal hidden thrips. Indicator plants such as petunias, asters and fava beans show silvery feeding damage early and can serve as early-warning stations within a larger crop.
IPM for Thrips Pests
An effective integrated strategy against thrips includes exclusion methods such as fine insect screens and careful inspection of incoming plants. Using trap crops to concentrate and identify infestations is also helpful. Targeted chemical treatments timed for peak activity, combined with biological controls, provide a comprehensive program.
Biological agents — including predatory mites Amblyseius cucumeris (foliar) and Stratiolaelaps scimitus (soil) — target different stages of the thrips lifecycle. Together with Orius insidiosus for outbreaks, these preventive and curative biocontrols significantly improve outcomes.
Some Advice
Thrips have an unusual development — somewhere between complete and incomplete metamorphosis. For at least some species, two stages (prepupa and pupa) are spent in the soil, growing medium or other friable materials. They fall off the plant to pupate underground. The good news is that with the right tools they can easily be controlled down there. Predatory soil mites — particularly Stratiolaelaps scimitus — hunt thrips pupae efficiently and persist in the media as a standing defense.
Not all thrips species drop to the soil to pupate, but the majority of those that growers worry about do — including western flower thrips (Frankliniella occidentalis), the most economically damaging species and the primary vector of INSV and TSWV.
Signs of Thrips Infestation
Look for silvery or distorted foliage, aborted fruits and vegetables, and tiny black fecal specks on leaf undersides. Recognizing these early signs allows prompt intervention, preventing broader infestation. Curled, deformed new growth from feeding inside developing buds is another classic giveaway.
Growers can use a wide range of monitoring tools. Yellow sticky traps are effective, but if you’re running biological control agents for other pests, blue sticky traps are also very good at capturing thrips while sparing some of the beneficials that yellow tends to attract.
A thrips program that ignores the soil is half a program. Pair foliar predators with Stratiolaelaps in the media and you’ll close the lifecycle loop.
For over 30 years, Green Methods has been a leader in the production and application of beneficial organisms used in biological pest control and integrated pest management programs.
