As daylight shortens and temperatures cool, pest dynamics in greenhouses and homes begin to shift — Thrips, whiteflies, fungus gnats, and other pests do not disappear in winter; they adapt. Many move into sheltered microclimates, linger in root zones, or persist in the smallest crevices of a structure.
For growers, this seasonal shift marks a critical time to reset, refresh, and reinforce your Integrated Pest Management (IPM) strategy. A robust fall and winter IPM program ensures a smooth transition into spring with fewer pest pressures and a healthier biological balance.
🍂 Why Winter IPM Matters
Even though pest populations tend to slow down in cooler temperatures, greenhouses and indoor environments provide warmth and humidity that pests can exploit. Many species continue to breed in smaller numbers or diapause throughout winter, waiting for the first increase in temperature or light to surge again.
Not acting now can result in sudden pest explosions in the following season — catching growers off-guard just as production ramps up. By contrast, growers who keep a steady preventive approach in winter often start spring ahead of the curve, with fewer outbreaks and stronger beneficial populations.
Key pest challenges that persist in winter include:
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Thrips: Populations decline more slowly than expected in warm greenhouse conditions. Most life cycle stages can survive winter in protected areas, like under plant debris or in soil.
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Whiteflies: Adults stay active at moderate greenhouse or indoor temperatures and can quickly rebound as temperatures increase.
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Fungus gnats: These thrive in damp media, especially when watering frequency stays high despite reduced plant uptake.
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Aphids: Indoors or in greenhouses, aphids can survive the winter in all life stages, continuing to reproduce on suitable host plants. Outdoors, most species overwinter as eggs laid on host plants in late fall, allowing them to hatch and re-establish populations when temperatures rise in spring.
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Spider Mites: These pests can enter indoor environments by hitchhiking on new plants, as well as survive on existing plants in a dormant state known as diapause. Additionally, they can overwinter as eggs in protected areas, ready to appear when conditions become favorable.
Understanding the above allows growers to plan their winter IPM program around prevention rather than spring reaction.
🪱 Entonem — Soil-Level Control That Works in the Cold
Entonem (Steinernema feltiae) offers consistent control of fungus gnat larvae, thrips pupae, and black vine weevil larvae even when soil temperatures drop.
Trials simulating fluctuating day/night regimes (5–13°C) show that Entonem stays active from a lower threshold of 5°C, making it a reliable cold-weather biocontrol agent.
Application Tips:
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Apply Entonem to moist soil; nematodes move through thin water films between soil particles.
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Avoid application in dry or waterlogged substrates.
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Maintain consistent moisture for at least two weeks post-application to ensure movement and infection.
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Reapply every 3–4 weeks if pest pressure or environmental conditions persist.
🕷️ Predatory Mites That Thrive in Cooler Conditions
While some beneficial insects slow down in colder months, several predatory mite species stay active and continue suppressing pest populations.
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If your greenhouse stays above 13°C and keeps humidity over 70%, these predatory mites can set up and provide early protection throughout winter.
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For home growers with warmer (above 18°C) but drier environments (below 70% RH), use Swirski & Spical Ulti-Mite sachets every 4 weeks to provide a continuous release of Amblyseius swirskii and Neoseiulus californicus for the prevention and control of whitefly, spider mites, and thrips.
🧭 Winter Pest Prevention Checklist
Building a proactive prevention plan now keeps your IPM program strong throughout the cold months.
1. Introduce Preventive Beneficials
If your greenhouse or home conditions are favorable, continue to use predatory mites throughout the fall and winter months. By the time pest activity picks up, your beneficials will already be in place and feeding.
2. Monitor Flying Insects
Hang yellow Horiver cards or roller traps throughout your growing space. These traps capture flying pests such as whiteflies, fungus gnats, aphids, and thrips, helping you track early infestations. Check and replace them regularly.
3. Treat the Soil
Apply Entonem when soil temperatures stay above 5°C. Even if pest numbers appear low, larvae or pupae may be dormant unseen in the substrate. Preventive soil treatments reduce the next generation before it appears.
4. Adjust Watering Practices
As daylight decreases and plants slow their metabolism, their water uptake also declines. Continue watering at summer frequency, and you risk over-saturating the soil — creating ideal conditions for fungus gnats, root disease, and algae. Reduce watering frequency and check soil moisture levels carefully.
5. Maintain Sanitation
Remove plant debris, algae, and fallen leaves from benches and walkways. Clean irrigation lines and gutters where pest eggs or larvae can hide. Sanitation remains the most overlooked — yet most effective — pest prevention tool.
6. Quarantine Incoming Plants
Any plants brought into your greenhouse or home can carry hidden pests such as aphids, spider mites, whiteflies, or thrips. Always isolate new plants for at least two weeks and inspect the undersides of leaves closely before integrating them with your main collection.
7. Maintain Environmental Stability
Greenhouses: Fluctuating humidity or temperature can stress beneficial insects and encourage pest reproduction. Where possible, keep humidity between 65–75% and avoid temperature drops below 13°C for predatory mites. Small adjustments can have a significant impact on the success of your IPM program.
Indoor Homes: Maintain 18-25°C. Do not worry about humidity, as the Ulti-Mite sachets were specifically designed to be used in low-humidity growing conditions. They will release new predatory mites onto your plants over a 4–5-week period.
8. Inspect Structural Areas
Pests often overwinter in greenhouse cracks, under benches, and around fan housings. Conduct a thorough inspection and clean these areas before winter sets in.
9. Review and Record
Use winter downtime to analyze pest monitoring data from the past year. Find hotspots and patterns to adjust your biocontrol strategy. Good records help you plan releases more effectively next season.
🌱 Supporting Beneficial Populations in Winter with Supplementary Feeding
Even in winter, supporting healthy populations of beneficial insects and mites is key to preventing pest outbreaks. When pests are scarce, beneficials may struggle to survive or reproduce — which is where supplementary feeding comes in. Providing alternative food sources keeps your natural enemies active and ready to respond once pest populations increase.
Koppert Canada offers a range of supplementary feeding products designed to support your biocontrol agents throughout the fall/winter months:
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Nutari – A feeder mite supplement for predatory mites, encouraging feeding and reproduction even when pest densities are low.
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Entofood – Provides essential nutrients for various predatory insects, supporting survival and activity in low-prey conditions.
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Nutemia – A mix of ingredients that sustains mites and small predators over longer periods, reducing the need for frequent applications.
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Artefeed – Brine shrimp cysts for beneficials, ensuring consistent development and longevity of predator populations.
Key benefits of supplementary feeding:
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Keeps predatory mites and insects active when prey is limited.
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Boosts reproduction and establishment, ensuring your biocontrol system stays strong.
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Supports early-season preventive releases, giving you a head start on pest suppression.
By integrating these products into your winter IPM program, you provide your beneficials with the resources they need to thrive — read more here: Supplementary Feeding for Biological Control: A Complete Guide | Koppert Canada
🍂 Staying Ahead of the Season
Every season brings new pest challenges — but nature provides year-round allies. By aligning your biocontrol releases with environmental conditions, you strengthen your IPM program from the ground up.
Whether you are managing a commercial greenhouse or tending to a winter crop at home, a proactive approach now will set the stage for healthy, resilient plants in spring.
Let us keep fighting nature with nature — all year long. 💪🌱
