Winter pest control is quiet work. Most insects are dormant, hidden in soil, bark and debris, and the pests that matter in winter are the ones you can see: mice, voles and rabbits gnawing bark, pests in stored crops, and the insects that thrive in the warm, still air of a greenhouse. Winter is also the season to plan next year's pest control, to clean and prepare, and to check the garden regularly, since a problem caught in winter is far easier to deal with than a problem that has had all spring to grow.
The winter pest routine is: protect bark, check stores, inspect the greenhouse, clean up, and plan. Each job is small, but together they stop winter damage and set up a cleaner spring. This guide covers the pests that matter in winter, what to do about each, and how to use the quiet months well. If a pest problem is severe or you are unsure what you are dealing with, use our pest identifier helper and check your local extension service.
Mice, voles and rabbits: protecting bark
Mice, voles and rabbits are the main winter pests in the open garden, because they gnaw bark when other food is scarce, and they do it unseen, under snow, mulch or long grass. A young tree girdled — bark eaten all the way around the trunk — will die, since water and nutrients can no longer move between roots and leaves, and the damage is often not noticed until spring, when the tree fails to leaf. Protect the trunks of young fruit trees and shrubs with a guard: a spiral guard, wire mesh or hessian wrap, fitted snugly and checked regularly. Our fall fruit care guide covers trunk guards, and our guides to voles in garden, mice in garden and rabbits in garden cover those animals in detail.
Keep mulch and long grass away from the base of young trees, since they shelter animals and hide their damage. Mow or strim grass around trees in fall, and keep mulch a few inches from the trunk. Check guards and trunks regularly through winter, especially after snow, since snow can let animals reach higher up the trunk than they otherwise could, and a guard that has slipped or been damaged is no protection at all. Remove guards in spring, once growth resumes, so they do not harbour pests or damage bark as the tree grows. If bark has been gnawed, clean the wound, remove loose bark, and let the tree heal; a tree girdled all the way around will not recover, and it should be replaced.
Checking stored crops
Stored crops are vulnerable to pests all winter. Potatoes, onions, garlic, squash and apples stored for winter can be damaged by mice and rats, which eat them and spread disease, and by insects that thrive in warm stores. Check stores regularly through winter, removing anything soft, mouldy or smelly before it infects the rest, and look for droppings, gnaw marks and other signs of rodents. Our fall harvesting guide covers storing the harvest, and our fall pest control guide covers the fall pest routine that leads into winter storage.
Keep stores cool, dry and ventilated, since warm, damp stores invite rot and insects, and use sealed containers or wire mesh where mice are a problem. Store only sound, undamaged produce, since damaged items rot first and spread rot to the rest. Do not use poison in a food store, since it can contaminate produce and harm pets and wildlife; use traps and exclusion instead, and check your local extension service for rodent control that is safe around food. In zones 11 to 13, where plants keep growing year-round and there is no dormant season, stored-crop pests are less of a winter issue, since the garden keeps producing — see the zone 11 winter gardening guide.
Greenhouse and indoor pests in winter
A greenhouse in winter is warm, still and humid, which suits pests far better than it suits plants. Aphids, whiteflies, spider mites and mealybugs can all thrive in a greenhouse through winter, building up numbers on overwintering plants and spreading to new seedlings in spring. Inspect greenhouse plants regularly, checking leaf undersides and stems, and remove infested leaves at once. Ventilate on mild days, since still air favours pests and disease, and keep the greenhouse clean, removing dead leaves and debris. Our guides to aphids control, whiteflies control, spider mites on plants and mealybugs on plants cover the main greenhouse pests.
Houseplants can also suffer pest problems in winter, since dry indoor air favours spider mites and the pests that came in with the plant in fall can build up over winter. Check houseplants regularly, isolate any plant with pests, and wash leaves to remove them. Fungus gnats thrive in damp compost indoors in winter — see our fungus gnats guide — and letting compost dry out between waterings is the best control. Our fall houseplant care guide covers bringing plants in and the indoor rules for winter. Do not spray broad-spectrum insecticide indoors or in a greenhouse as a routine, since it harms beneficial insects and can be unsafe in an enclosed space.
Dormant pests and planning for spring
Many pests spend winter dormant in the garden: aphid eggs on bark, scale insects on stems, vine weevil grubs in pots, and disease spores on fallen leaves and debris. Winter is the time to reduce those numbers by cleaning up. Clear fallen leaves from under fruit trees and roses, remove mummified fruit from trees, and cut out diseased wood when you prune — see our winter pruning guide for the method and our brown rot fruit guide for why mummified fruit matters. Check pots for vine weevil grubs when you repot or move them, and remove and destroy badly affected plants rather than composting them.
Winter is also the time to plan next year's pest control. Note which pests were a problem this year, so you can watch for them early next year, and plan rotations so the same crop does not go back into the same bed, which lets soil-borne pests and disease build up. Plan to encourage predators — ladybirds, lacewings, hoverflies and birds — by leaving some undisturbed corners and planting flowers that attract them. Order biological controls early if you use them, since they need to be applied at the right time and in the right conditions. And check your local extension service for advice on pest cycles in your area, so spring control starts at the right moment rather than too late.
Common winter pest mistakes
The most common mistake is forgetting to protect young trees from animals, so a tree is girdled in a single winter. The second is neglecting stored crops, so a single rotting item spoils a whole store. The third is ignoring greenhouse pests through winter, so they build up and attack spring seedlings. The fourth is leaving diseased material and fallen leaves in the garden, which lets disease overwinter and reinfect plants in spring. The fifth is using poison in a food store, which is unsafe. The sixth is spraying broad-spectrum insecticide in winter, which kills beneficial insects and is often wasted on dormant pests. And the seventh is doing nothing all winter and hoping pests will disappear, when a little checking and cleaning in winter saves a great deal of fighting in spring.
Frequently asked questions
What pests are a problem in winter?
Mice, voles and rabbits gnawing bark, rodents in stored crops, and aphids, whiteflies, spider mites and mealybugs in greenhouses and indoors. Most outdoor insects are dormant in winter.
How do I protect young trees from mice and voles?
Use a trunk guard, keep mulch and long grass away from the base, and check guards and trunks regularly through winter, especially after snow. Remove guards in spring.
How often should I check stored crops in winter?
Regularly, at least every couple of weeks. Remove anything soft, mouldy or smelly at once, look for droppings and gnaw marks, and keep stores cool, dry and ventilated.
Should I spray for pests in winter?
Usually not. Winter pest control is mostly protection, checking and cleaning up, not spraying. Broad sprays kill beneficial insects and are often wasted on dormant pests.
How do I plan pest control for spring?
Note which pests were a problem this year, plan rotations, encourage predators, and order biological controls early. If you are unsure, check your local extension service.