Valentine’s Day orders are (finally) out the door, and it’s time to shift focus to what’s next: gearing up for spring production. But if you're growing potted flowers like chrysanthemums, geraniums, begonias, or gerberas, you know one thing for sure: Western Flower Thrips aren’t taking a break just because it’s cold outside.
Winter production brings unique challenges with managing Western Flower Thrips: slower life cycles, darker color morphs that blend in better, and populations congregating in warmer microclimates inside the greenhouse. Staying ahead of thrips doesn't have to be complicated, and taking action now will mean fewer headaches when spring crops hit full swing.
Here are 5 key strategies for keeping thrips, and unnecessary costs, at bay while maintaining high production quality that your customers will love.
Understanding Thrips Behavior in the Winter (And Why They’re Still a Problem)
Thrips don’t disappear in winter — they just adapt. Slower life cycles and reduced movement might make thrips seem like they’re less of an issue, but that’s not the case.
Sneaky Survival
With greenhouse heat zones creating microclimates, thrips congregate in warm spots, especially flower buds and under foliage, making them hard to reach with sprays.
Slower Development
Cooler temperatures drastically extend the thrips lifecycle. At 60°F (15°C), thrips can take up to 44 days to go from egg to adult. That means populations can build up gradually, and by the time you see real damage, you’re already behind.
Darker Morphs
Thrips adapt to the cold. You'll often see darker colored adults during the winter months. They may seem less active, but they're still feeding and reproducing, albeit slower.
1) Monitoring: Scout Smarter, not Harder
Keeping an eye on thrips now prevents surprises when temperatures warm up. A strong monitoring program makes all the difference in deciding when and where to act.
Sticky Trap Placement
This is your first line of defense. Position blue or yellow sticky traps strategically — near heat sources, doorways, and areas with a history of thrips infestations. Remember, thrips might be sluggish in winter, so check traps regularly, but don't expect huge numbers.
Blue traps are more effective at detecting low densities of Western Flower Thrips, while yellow traps catch a broader range of thrips species. Use green sticky traps if you are concerned about Echinothrips americanus.
For side-venting greenhouse structures, place traps within 2 to 13 ft. of vent openings to optimize monitoring and trapping of incoming thrips populations.
White Tray Tapping
Tap foliage and flowers over a white tray to dislodge thrips and get an accurate count. Focus on new growth and buds.
Increase inspection frequency to at least twice a week for high value varieties as the weather becomes warmer.
Record Keeping
Track your findings! Note thrips counts, locations, and plant damage. This data will help you identify hotspots and evaluate the effectiveness of your preventative measures.
2) Biological Control: What Works (And What Needs a Boost) in Winter
Biologicals are still a powerful first line of defense against thrips in the winter, but they work slower due to colder temperatures. Here’s how to make it work in winter, and reduce the need for chemical controls:
This predatory mite is your primary weapon against thrips larvae, and these mites can easily target thrips that newly hatches from eggs.
Amblyseius cucumeris are active predators above 50°F (10°C), but their development is slower. To compensate, increase release rates and prioritize releases in warmer greenhouse areas or during the warmest parts of the day.
Routinely check for the presence of active predatory mites in the crop.
These soil-dwelling predatory mites target Western Flower Thrips pupae in the growing media (as well as Onion Thrips and Thrips parvispinus pupae, but not Echinothrips americanus).
Since thrips development is slower in the winter, these predators are useful for longer periods. Targeting thrips pupae will reduce the number that will develop into adults.
Beneficial nematodes, like Steinernema feltiae, can be highly effective at controlling thrips pupae in the growing media. Apply them via boom spray or drench, ensuring good coverage of the growing media.
Maintain adequate soil moisture for optimal nematode activity.
3) Cultural Controls: Small Changes, Big Impact
Adapting cultural practices is crucial for managing thrips populations cost-effectively in winter conditions, as thrips can exploit gaps in key processes – leading to excessive biological and chemical control costs just to get populations under control.
Sanitation
Remove plant debris promptly, as it can harbor thrips populations.
Implement strict hygiene measures for workers and equipment moving from separated greenhouse zones with higher levels of thrips infestation to cleaner zones.
Temperature Zones
While maintaining optimal growing temperatures for your varieties, consider creating "hot spots" in the greenhouse.
Use localized heating to create areas where thrips can congregate, making them easier to target with control measures.
4) Chemical Intervention: Targeted and Timed
If thrips pressure increases and you need to spray, make it count. Thrips populations in winter are more exposed due to slower movement and feeding, so well-timed applications are highly effective.
Product Selection:
Choose products with translaminar activity to reach thrips hiding in the plant structure. Rotate between different modes of action to mitigate resistance. Insect growth regulators (IGRs) can be particularly effective against slower-developing winter populations of thrips.
Thrips move less in cooler weather, but they’re most active in warmer parts of the day. Schedule sprays accordingly to maximize impact.
Keep your biocontrol populations in mind — some chemicals and application methods are relatively safer for your bios, such as localized drenches of Flonicamid (Beleaf® 50SG Insecticide), but others can wipe out bios populations, and leave residuals that can impede further establishment.
5) Fine-Tuning the Strategy for the Push to Spring
Now’s the time to dial-in your thrips management strategy before spring production kicks into high gear. Here’s how to stay proactive, and prevent unexpected costs from straining your budget:
Track What's Working, and What's not
Keep a simple spreadsheet or use a pest monitoring app to log trap counts, sprays, biocontrol releases, and discards due to thrips damage — so you can correlate crop protection input costs to the level of control achieved. Data-driven decisions save money.
On a weekly or monthly basis, evaluate the performance of your strategy with 4 simple questions to drive continuous improvement:
What's working, and how much money or production are we saving?
What's not working, and how much are we at risk of losing?
What have we learnt?
What are 3 quick improvements we can make, to save more money or production?
Refresher Training
Now’s a good time for refresher training on thrips identification, best scouting practices, and correct biocontrol application techniques for your team.
Make sure everyone is on the same page, and focused on making this spring's production as successful as possible.
Final Thoughts
Winter thrips control isn’t about elimination — it’s about cost-effective containment so populations don’t explode when warmer weather arrives. You’ve got production targets to hit, and every decision you make now sets the tone for a smooth, profitable spring season.
By adjusting monitoring, dialing in biocontrol usage, and making strategic chemical choices, you can save more of your production from thrips damage, without spending over your budget.
If you want a customized thrips management plan tailored for your varieties, location, and budget, connect with our Technical Consultants. All you need to do is schedule a call or visit today, and we’ll walk through your current program, identify gaps, and make sure you’re set up with a cost-reducing thrips management plan before temperatures rise.
Spring’s coming fast — make sure you’re ready.