Not all garden pests have called it quits

Garden pests can do plenty of damage in spring and summer, but they can come close to destroying a garden in winter.

Instead of tiny bugs and beetles, the pests you're likely to encounter this time of year will be the four-footed kind that can munch on small branches or eat the bark off young trees. If you notice something going after your trees and shrubs this winter, it's probably one of the usual suspects: voles, rabbits or deer.

Once we've got a layer of snow on the ground, it's fairly easy to tell the difference between the damage caused by these critters. Voles tunnel beneath the snow and chew on tree or shrub bark at the surface of the soil. Rabbits feed a little bit higher. Instead of tunneling, they hop on top of the snow. So you'll notice signs of their gnawing just above the snow line.

Deer take a two-pronged attack. They chew on twigs and small branches and bucks can rub their antlers on trees to attract females. Signs of deer damage typically show up higher in a tree or shrub than rabbits can reach.

Wrapping

OK, I've helped you identify the culprits. Now, you probably want to know what you can do about it.

The simplest and surest way to prevent damage from voles and rabbits is to wrap your tree trunks. The tree wraps that work best are made of plastic and spiral around the trunk. There are paper wraps, but if an animal is hungry enough, it will chew right through the paper to reach the tender bark underneath.

If you do wrap your trees, make sure you remove the wrap in mid-spring. If you wait too long to remove the wrap, the tree won't be able to grow properly and may actually grow around the wrap. And wrap left on permanently can even strangle a tree to death.

Did that scare you off using them? There are a few other ways you can protect your trees.

Trapping, repellents

Trapping voles and rabbits is an option, but not a very effective one. In most yards, the ones you trap and remove will just be replaced by others.

A better bet is to try using repellents. The castor-oil based repellents available at garden centers work quite well against little critters and can last for up to six months. And there are many different kinds of repellents that may keep deer at bay. There's hot pepper, dried blood, human hair, dog urine and a whole host of others.

Several researchers have tested these concoctions and found that the ones with "putrescent egg solids" (which is a cute way of saying rotten eggs) work most reliably. So if you want to shoo deer away, pick up a commercial repellent with eggs in it.

You also can mix up a deer repellent yourself. Just blend four eggs with a quart of water, pour into a spray bottle, and go to it. A homemade spray like this may repel deer for up to two weeks before you need to reapply.

And that leads us to one of the problems with using repellents in winter: Spraying in freezing temperatures isn't as effective as spraying when it's warmer. And, when it's really cold, going outside to spray isn't much fun. If possible, try to apply repellents when it's above freezing.

Remember, there's no sure-fire way to completely rid your garden of pests, even in the winter. But with time and a never-say-die attitude, you can prevent them from doing their worst.

Jeff Gillman is an associate professor of horticulture at the University of Minnesota. He's also the author of three books, "How Trees Die," "The Truth About Garden Remedies" and "The Truth About Organic Gardening" (Timber Press, $12.95).

--Jeff Gillman