News
Managing Thrips Parvispinus: New Research on Cultural and Biological Control
June 20, 2025
Over the past few years, Thrips parvispinus has emerged as a serious threat to ornamental greenhouse crops across North America. First reported in Florida in 2020 on Hoya and Anthurium, this invasive thrips has now been detected in greenhouse ornamentals, peppers, and landscape plants in the southeastern U.S., and more recently in Ontario. While it can’t survive winters outdoors in Canada and parts of the northern U.S., its wide host range—including Mandevilla, Dipladenia, Schefflera, Ficus, and peppers—means it has the potential to cause significant damage wherever susceptible crops are grown.
Growers have reported stunted growth, leaf streaking, and floral damage that reduce crop quality and marketability. Complicating matters, T. parvispinus is suspected of developing pesticide resistance, making conventional chemical controls less reliable. Biological control programs designed for other thrips species, like Frankliniella occidentalis (western flower thrips), also appear less effective against this pest.
With support from the American Floral Endowment, researchers Dr. Rose Buitenhuis (Vineland Research and Innovation Centre) and Dr. Sarah Jandricic (Ontario Ministry of Agriculture, Food and Agribusiness) have launched a multi-year effort to develop practical, sustainable IPM strategies tailored specifically for T. parvispinus. The first year of research focused on three main areas: cutting dips, thrips biology and behavior, and evaluating biopesticides and predators. Here’s what they found:
Clean Start: Cutting Dips and Phytotoxicity
Because T. parvispinus does not yet appear to be spreading outdoors in most of North America, infested plant material, particularly unrooted cuttings, is likely the primary source of new introductions. Clean start practices like cutting dips are a critical first line of defense.
Researchers evaluated the phytotoxicity of several dip treatments on unrooted and rooted cuttings of Mandevilla, Hibiscus, and Anthurium. These included commercial biopesticides like Suffoil-X, Botanigard, BioCeres, Mycotal, and LalGuard M52, as well as experimental treatments like UV-C light plus hydrogen peroxide or ozone.
Key findings:
- Most treatments were safe for unrooted Mandevilla and Anthurium.
- Hibiscus plugs were more sensitive, especially to oil-based products and LalGuard M52, which caused damage at all rates tested.
- Mycotal was safe on unrooted Hibiscus but not on rooted plugs.
- Short UV-C exposure combined with hydrogen peroxide caused no significant damage; longer exposures damaged rooted plugs but were tolerated by unrooted cuttings.
Takeaway: Cutting dips offer a promising way to intercept thrips before they enter production, but product selection and crop-specific sensitivity must be considered.
Understanding Thrips Behavior to Improve Control
Standard biological control agents used for western flower thrips often underperform against T. parvispinus. To improve management strategies, researchers are investigating this thrips’ unique biology and behavior, focusing on activity patterns, host plant effects, and developmental timing.
Flight Activity (Diel Behavior)
Monitoring in a commercial Anthurium greenhouse showed that flight activity increases steadily throughout the day and remains high into the late afternoon. Thrips showed directional preferences, favoring southeast-facing trap surfaces in the morning and northwest-facing sides in early afternoon, suggesting potential windows for targeted interventions.
Oviposition and Development on Different Hosts
When reared on bean, pepper, and Mandevilla:
- Egg-laying was highest on beans and lowest on Mandevilla.
- Later-stage development slowed significantly on Mandevilla, with only 40% of thrips reaching adulthood (vs. 85% on pepper).
- Older Mandevilla leaves delayed development even more, suggesting they are less suitable for thrips development.
Takeaway: Mandevilla, particularly older leaves, may be less favorable hosts for T. parvispinus, which could guide scouting efforts and cultural strategies.
Biocontrol Agents Show Promise
New trials focused on evaluating two predatory species: Orius insidiosus (minute pirate bug) and Anystis baccarum (a predatory mite known as the crazee mite). Both showed strong potential to suppress T. parvispinus.
In 24-hour lab trials:
- O. insidiosus reduced adult thrips populations by 86%.
- A. baccarum achieved 91% control.
In 8-week-long greenhouse cage studies:
- Predator releases reduced T. parvispinus populations by ~80%, with O. insidiosus producing offspring by week 4 and A. baccarum by week 8.
Takeaway: Both predators could be viable options in an IPM program targeting T. parvispinus, especially when used proactively and in combination with clean plant material protocols.
What’s Next?
The research team is now expanding their work for years 2 and 3 of this project:
- Testing dip efficacy and safety in commercial greenhouse conditions.
- Continuing T. parvispinus behavioral studies to identify key intervention points.
- Evaluating additional biopesticides and predator species for compatibility and effectiveness in T. parvispinus control.
Impact for the Industry
This research will deliver much-needed tools for ornamental growers facing this fast-spreading pest. By integrating cutting dips, biological insights, and compatible control agents, the goal is to build a reliable, resistance-conscious management strategy for T. parvispinus. Clean plants, reduced pesticide use, and targeted biocontrol can translate into real savings (and peace of mind) for growers.
Stay tuned for further updates and practical recommendations as this work progresses over the next two years. Also, don’t miss Dr. Buitenhuis’s tHRIve session on this AFE-funded research at Cultivate, where she will be presenting on Sunday, July 13th from 11:15 – 12:15 pm in room C170. We’d love to see you there!
