9 Worst Garden Pests and How to Get Rid of Them
Updated: Jul. 25, 2024
As if weeds and weird weather weren't bad enough, gardeners also have to face insect pests. Here's how to deal with them.
Do you garden? I do, and every year, I watch my tomatoes and lettuce get nibbled or stripped down to the dirt by critters of all stripes. Garden pests reduce harvests and frustrate gardeners who spend time and money trying to keep them away, often to no avail. “Animal damage is one of the most common questions we get in the Plant Clinic,” says Spencer Campbell, who manages the clinic at the Morton Arboretum in Lisle, Illinois.
Knowing the animal that’s causing the damage will determine the action you can take to remedy it, Campbell says. Campbell and Plant Clinic staff answer 10,000 questions a year from all over the world, and you can bet many of those are about garden pests.
Ahead, we talk to Campbell about the various animals at work in your yard and what you can do about them so you can spend less time being annoyed and more time enjoying your tasty garden harvest.
Deer
You’ll see deer damage mostly in the fall during rutting season “when they’re trying to take the velvet off their antlers,” Campbell says. Deer love young, pliable trees that have a little stiffness to them, like oaks. “Ones you can kind of wrap your hand around, like about an inch caliper,” Campbell says.
“The best way to manage for that is to put corrugated plastic pipe around the trunk of the trees,” the expert says. These flexible tubes split lengthwise and wrap right around the trunk. Another good choice is to create a physical barrier around the tree with stakes and/or hardware cloth, which is similar to chicken wire but with a finer mesh.
“During the winter, deer might like to eat little buds on young trees,” Campbell says, but building a blocker around your trees can get deer to move on. Get some 2×2 stakes, about 4-6 feet tall, and stake them around your tree. Often, Campbell doesn’t even use the cloth. Just the act of bumping into the stakes can be enough for deer to look elsewhere.
Another tip that works for many garden pests is strategic planting, aka sacrificial lambs. Campbell often places his more desirable plants further back in the garden or behind plants that he doesn’t mind losing.
Chipmunks
“Chipmunks eat your tomatoes, and they’ll just take one bite and run away,” Campbell says. “They’re the bane of my existence.” For these crafty critters, Campbell suggests a physical barrier such as a fine mesh insect or bird netting. Drape it over your vegetable garden and ensure they can’t get under.
“Chipmunks also like to dig, so they’ll often go in your container plantings, like annuals,” Campbell says. Place hardware cloth around your plantings to keep the digging to a minimum. “They’re not going to dig from underneath, but if they run into that metal, they may not want to keep eating there,” Campbell says.
Chipmunks can wiggle under your garage door, so make sure the rubber gasket is intact and keep birdseed tightly covered. Sometimes, you’ll see repellents based on smell, but Campbell isn’t sold on their effectiveness. “I would only use those in conjunction with another method because by themselves, the rain will wash them away, and you’ll have to reapply.”
Moles
Moles spend most of their lives underground searching for insects, so you likely won’t see them. But you will see their tunnels. This can really disturb your turfgrass, Campbell says. “The best management is, frankly, to have a service come out and manage for them.”
“There’s a reason the game’s called Whack-a-Mole,” Campbell says. They’re difficult to eradicate, to say the least. Ecology experts at the University of Wisconsin say traps are effective and humane, so if you’re willing to do that dirty work, mole traps are widely available, but it’s important to set them correctly. Poisons are ineffective because moles will sniff it out and avoid the tunnel.
Finally, indirect control can work. Since moles are always looking for food, controlling the grub population under your lawn can make them move on and look elsewhere for their meals.
Squirrels
Cute, clever squirrels are highly adapted to life around people, so this one you’re likely going to have to live with. “They’ve figured out a solution to thrive in the environments we’ve constructed,” Campbell says. You can minimize the damage to your garden and container plantings like you do chipmunks, with physical barriers like fine-mesh hardware cloth.
As far as trees go, they’re mostly just a nuisance. “Squirrels will chew off branches to make their nests, so you’ll see small branches in your yard from your mature trees,” Campbell says. “If you notice two teeth marks on the edge of the branches, that’s a tell-tale sign of a squirrel.” They also eat some woody plants and chew on the bark of mature trees.
Keeping your home sealed up tight will prevent them from stashing acorns in your attic and garage, so look for holes and other potential entry points. Feeding them peanuts or trying to lure them away from your plants will bring in more squirrel friends. “At the end of the day, a dog’s still a dog, and a squirrel’s still a squirrel,” Campbell says. “The best thing to do is have sacrificial plants, or just plan on picking up the branches they leave behind.”
Rabbits
Rabbits will eat almost anything. Flowering plants, veggies, you name it. “They will chew it down to the ground,” Campbell says. “You’ll just see the stumps left over or the stems without any leaves.” In larger gardens, Campbell likes using “sacrificial lambs,” aka planting things you know you’ll lose. “I have this one hosta that they just love, so I just put it around the edges and say, ‘That’s yours.'”
But while he likes feeding the wildlife, Campbell knows many people don’t have that much real estate. If that’s the case, “the only way to keep them out is a physical barrier,” Campbell says. Use chicken wire or hardware cloth, and if you don’t like the look of it, dress it up a bit. “You can always paint the screening black, so it doesn’t reflect light and it blends in better.”
One more tip that works with bunnies: If you have a dog, let him in the backyard often so the rabbits sense a threat and move elsewhere.
Woodpeckers
When woodpeckers go to town on your trees, they’re looking for insects. “Sometimes when they do that, they can cause lasting impacts by removing bark on trees and making large holes and cavities,” Campbell says. “But that’s kind of good for other wildlife in some regards.” Plus, woodpeckers have the most luck finding insects on sick or diseased trees, so their presence is often a sign something else is wrong.
“You’d be surprised at the number of woodpecker questions we get here,” Campbell says. People try all sorts of things to get rid of them, and many of them are wrong. Never wrap your tree in tin foil or insulating foam. These can cause serious impacts to your tree and wildlife. If your tree is diseased, removing it will help redirect woodpeckers to other habitats, but Campbell says one of the best things you can do is provide food, like suet cakes, that woodpeckers like.
Slugs
Slugs love hostas, Campbell says, as well as other ornamental plants, and they leave behind large, irregular holes in the leaves. Slugs prefer shady, cool and moist areas, so they’re less likely to bother plants that grow in full sun. Because they don’t have shells like a snail, they exude a slime that leaves a visible trail. Look under leaves or in damp areas in the morning. (They often feed at night.)
Campbell says the best way to get rid of them is to use old beer. Set out a jar or shallow dish of beer, and “they’ll die in a watery grave.” Removing prime slug habitat, like constant damp or shady areas, can also help. Of course, you can always just pick them off with your fingers and dispatch them if you’re so inclined.
Voles
Campbell says the Plant Clinic gets many questions about voles, which are small rodents that tunnel through your grass. (Not to be confused with moles, which tunnel underground and are not rodents.) “They’re like little tiny mice,” Campbell says. Voles are herbivores, and “they’re going after things with tubers and thick root systems.”
To stop them, Campbell says exclusion helps. “If you notice they keep eating specific plants, bury hardware cloth underneath, where you know you’re going to plant them every year.” Another clever deterrent is called a “cloche,” which is a bell-jar looking contraption that goes over a plant. This will deter squirrels, chipmunks, birds and many other pests, Campbell says.
Japanese Beetles
These transplants aren’t a pest in their native country, but in North America they can wreak havoc on a garden by defoliating leaves. “They can just take over,” Campbell says. Japanese beetle larva develop underground — they’re those white, plump, comma-shaped grubs that are buried under your turf grass — so managing starts with getting rid of the grubs.
The best way to control them is with chemical or biological agents. “Commercial traps and pheromone lures have shown to attract more beetles to your area, so we do not recommend them,” Campbell says. Instead, Campbell recommends applying beneficial nematodes in late July, which will infest the turf and kill the grubs. Or, you can apply a commercial insecticide (make sure to read the label.)
About the Expert
Spencer Campbell is the plant clinic manager at the Morton Arboretum in Lisle, Illinois, where he and Plant Clinic staff answer more than 10,000 plant questions each year from the public. Campbell got his start in environmental advocacy before turning to plant care and education.
Originally Published: June 24, 2020
