Quick Guide: Overwintering Insects & Mites
Oct 08, 2025
Cold weather doesn’t mean mite and problem free. Many species of thrips, spider mites and more survive winter by hiding in soil, root balls, bark crevices, and infrastructure. If those stages aren’t disrupted now, they can fuel early-season outbreaks that overwhelm your biological program.
This guide answers real-world questions about winter pest survival and includes a downloadable response guide to help you take action before spring.
Want the full science behind overwintering and biological strategies? Read: Understanding Overwintering Mites, Insects and Control Options - Natural Enemies
What Is Overwintering and Why Does It Matter?
Overwintering is how pests bridge the off-season—through diapause, pupation in soil, eggs on woody tissue, or slow reproduction in protected structures. These hidden stages emerge early and amplify spring populations, especially where microclimates keep media and canopy protected.
Why it matters:
- Carryover pests = early outbreaks that overwhelm first releases
- Microclimate beats weather—insulated pots, mulch, and covered bays protect pests
- Winter ≠ pest-free—heated or minimally heated structures allow slow but steady activity
Winter Pest FAQs
Do fungus gnats survive winter in soil?
Yes—especially in moist media and dense root balls. Freezing knocks some back outdoors, but insulated containers and greenhouses let them persist.
Solutions:
- Apply Entonem (Steinernema feltiae) before media drops below 50 °F (10 °C)
- Dry down media and improve drainage
- Use Horiver Yellow Sticky Traps to monitor adult activity
- Remove algae films and standing water that attract shore flies and fungus gnats
Should I replace or reuse potting soil before winter?
Not always. The bigger issue is old roots and debris that shelter larvae and pupae.
Solutions:
- Skim or replace the top 1–2 inches of media if reusing
- Add Continuum to stabilize microbial balance after heavy irrigation or chemical inputs
- Apply Entonem before deep cold to target larvae and pupae
- Break up dense root balls and discard heavily infested media
Will freezing temperatures kill spider mites?
Not reliably. Diapausing females hide in crown tissue, bark, and mulch where cold bites less.
Solutions:
- Remove debris and weeds near crowns
- Introduce Anso‑Mite (Amblyseius andersoni) in greenhouses for low-temp activity
- Avoid over-fertilizing dormant stock—lush tissue favors mites when temps rise
- Inspect bark crevices and crown tissue during winter maintenance
Looking for more information on predatory mites for spider mites? Check out our guide to Solving Spider Mites.
Do thrips survive winter?
Soil-pupating species like Thrips parvispinus and Western flower thrips persist as pupae in media and emerge when conditions improve. Species that complete more of the cycle on foliage rely on canopy refuges.
Solutions:
- Entonem drenches to target soil-pupating stages
- Limonica or Anso‑Mite for canopy-level suppression
- Remove weeds and canopy debris that shelter pupae
- Maintain sticky traps to detect early adult movement
Looking for more information on predatory mites for Thrips? Check out our guide to Solving Thrips.
Do I need to clean out my greenhouse before winter?
It can certainly help! —benches, trays, algae films, and floor cracks harbor pests.
Solutions:
- Remove debris, algae, and weeds; improve drainage
- Store trays upside-down; vacuum cracks and crevices
- Use Entomite‑M for soil-level pests in hard-to-reach spaces, sprinkle in media and crevices
- Sanitize irrigation lines and flush algae-prone zones
Overwintering Pest Survival Chart
| Pest | Overwintering Stage | Outdoors (Hard Frost) | Protected Structures |
|---|---|---|---|
| Fungus gnats | Larvae in media/root balls | Sometimes (insulated) | Yes |
| Thrips (T. parvispinus, WFT) | Pupae in soil; foliage refuges | Rare | Yes |
| Spider mites | Diapausing females (crowns/bark) | Rare (kills most) | Yes |
| Whiteflies | Nymphs/adults | No | Yes |
| Aphids | Eggs on woody tissue; slow colonies | Yes | Yes (colonies persist) |
| Leafminers | Pupae in debris/media | Rare | Yes |
| Mealybugs & scales | Crown tissue, bark, plant crevices | Rare | Yes |
| Japanese beetle grubs | Deep soil below frost line | Yes | N/A |
Pro Tip
Cold slows pests, but microclimates always win. Don’t count on winter to do your pest control—pair sanitation with cold-active biologicals for best results.
Want the full science behind overwintering and biological strategies?
Check Out: Understanding Overwintering Mites, Insects and Control Options - Natural Enemies
Seeing two-spotted spider mites, thrips or other problems and need to know what to do? Download our actionable guide here.
Additional Resources on overwintering & seasonal concerns for growers:
Overwintering pests: diapause or hibernation and the wait for spring | Koppert Global
Protect your crop when temperatures drop: The benefits of early crop protection | Koppert Global
