Managing Overwintered Pests in the Landscape

Dear friend,

I hope this letter finds you sipping something warm and watching the light shift ever so slightly day by day. Even though the wind can still bite, February has a way of hinting at changes to come. Around here, I’ll catch a glimpse of a daffodil shoot poking through the leaf litter or see the buds on the dogwood branches getting plump and pink. Spring’s approach is both subtle and insistent. But with it, I’m reminded of a less-welcome phenomenon: the return of garden pests. Yes, even as the snow might linger in shady spots, certain critters are already waking from their winter slumber, eager to munch on the fresh green bounty we’ve been dreaming about.

It might seem odd to think about pest management before your flowers have even bloomed or your veggies have sprouted. But in truth, a lot of insects and other pests overwinter in the soil, under leaf piles, or in the crevices of bark. By late winter, they’re gearing up for their own emergence, which often happens right alongside the tender new growth in our gardens. And if you wait until you see the holes in your cabbage leaves or the dreaded webbing on your shrubs, you’ve missed a valuable window of prevention.

Let’s start by talking about where overwintering pests like to hide. One classic example is the squash vine borer, which can wreak havoc on summer squash, zucchini, and pumpkins. The adult moths lay eggs at the base of the plants in mid-summer, and the larvae then burrow into the stems, often killing the plant. Once their feast is over, those larvae burrow into the soil to pupate, re-emerging as moths the following year. If you had a squash vine borer problem last summer, you can bet they may be wintering in your garden beds. Tilling the soil lightly (if you practice tilling) or even turning it with a spade can expose the pupae to cold temperatures and predators like birds, reducing their numbers.

Another common pest that overwinters is the Colorado potato beetle. These rascals burrow into the soil around the garden or hide in debris, waiting for spring to come out and chomp on your potatoes, eggplants, or tomatoes. Again, removing crop debris, rotating your crops, and lightly disturbing the soil can cut down on their comfy hiding spots. Crop rotation is especially helpful—if you don’t plant a host crop in the same spot, the emerging beetles might starve or at least have to travel farther to find their next meal.

Slugs and snails also harbor in cool, damp places, often under leaves, boards, or rocks. While they’re not insects, they can cause serious damage to seedlings and tender greens. A thorough garden cleanup in late winter, removing leftover plant material or piles of wet leaves, can reduce their hiding spots. As the weather warms, you can use slug traps, copper barriers, or even go on nighttime “slug hunts” (a headlamp and a bucket of soapy water in hand) to keep the population in check. And if you’re a fan of ducks or chickens, you’ll find they’re quite fond of snacking on slugs.

For tree and shrub pests—like scale insects or certain mites—you’ll often find them overwintering as eggs or adults tucked into bark crevices. A well-timed application of dormant oil spray can help smother them before they become active. Dormant oil is usually applied in late winter or early spring, when temperatures are above freezing but before the buds break. This oil effectively coats the pests and their eggs, cutting off their oxygen supply. It’s an old-school remedy but still widely used because it’s relatively gentle on beneficial insects (they’re mostly inactive in cold weather) and breaks down quickly. Just be sure to read the label instructions carefully, because some plants can be sensitive to oil sprays. And never apply it if there’s a risk of freezing that night or if the buds are already opening, because it can damage tender growth.

Now, let’s talk about beneficial insects, because they, too, overwinter. Ladybugs, lacewings, certain parasitic wasps, and other “good guys” often hibernate in leaf litter or hollow stems. That’s why it’s a balancing act when cleaning up the garden at the end of winter. On one hand, you want to remove hiding spots for pests. On the other hand, beneficials need safe harbors, too. One strategy is to leave some natural areas or designated “wild” spots where leaf litter and plant stems can remain, providing a habitat for helpful critters. In your main garden beds, though, you can still clear out diseased or pest-ridden material to reduce the threat next season.

Speaking of diseased material, plant diseases can also overwinter in the soil or on fallen foliage. If you had a bad case of powdery mildew or blight last year, removing and destroying affected leaves and stems in late winter can help prevent re-infection. Don’t compost them if they’re badly diseased (unless your compost pile gets hot enough to kill pathogens). Otherwise, you risk reintroducing the disease later on.

One more tip: look out for egg masses. Certain pests, like tent caterpillars, lay neat clusters of eggs on twigs that are easy to spot in winter. You can prune off those egg masses and dispose of them before they hatch into ravenous caterpillars. Take a stroll around your fruit trees or ornamental trees on a mild day, pruners in hand, and inspect for anything suspicious. Sometimes, you might find gypsy moth egg masses, which look like little patches of tan or buff-colored foam stuck to tree bark. Scraping them into a bucket of soapy water can save you a world of trouble later on.

It can be helpful to keep a garden journal or record of pest problems from the previous year. If you noticed that flea beetles were especially bad on your eggplants, or spider mites attacked your beans, jot it down. That way, you can focus your late-winter cleanup or preventive measures on those areas. By learning the life cycle of the pests that plague you most, you can time your interventions to when they’re most vulnerable. And believe me, intercepting them before they multiply can spare you a lot of grief once the garden is in full swing.

Now, you might be thinking, “Logan, this sounds like a lot of work—can’t I just wait until spring is in full bloom?” But taking steps now, while things are quieter, means you won’t be caught off guard. And, truth be told, I find a certain satisfaction in wandering the garden in late winter. The absence of leaves and flowers provides a clearer view of the structure: the bare branches, the contours of the land, the hidden nooks. If you’re willing to look closely, you’ll see the hints of life stirring—tiny buds forming, beneficial insects tucked away, perhaps a bird or two pecking at leftover seeds. This is a chance to commune with your garden in its resting state, to get a sense of what’s happening beneath the surface.

If, despite your best efforts, pests still show up come spring, don’t lose heart. No garden is ever completely pest-free. In fact, a healthy ecosystem includes a balance of pests and predators. The goal isn’t to eradicate every bug but to keep them in check so your plants thrive. If you manage the overwintering populations now, you give the beneficial insects a fighting chance to do their job when temperatures rise.

In closing, I encourage you to bundle up and take a quick stroll around your yard or garden beds. Peek under the leaf litter, take note of any egg masses, consider where pests might be hiding out. And then, make a plan—whether that’s raking away debris, turning the soil lightly, pruning off insect egg clusters, or lining up a dormant oil spray. These small efforts can pay big dividends when the warmth of spring finally settles in and we’re all dancing with delight at the sight of fresh sprouts and blossoms.

Stay cozy, stay vigilant, and remember that even in the quiet hush of February, your garden is alive with potential—both for good and for ill. By giving a little attention to overwintered pests now, you pave the way for a healthier, more vibrant growing season. And isn’t that what we all dream of when the days are still short and the wind howls around the eaves?

Yours in anticipation of a pest-aware spring,
Logan