8 ways to keep garden pests under control
Protect your precious veggies from enemy bugs, birds, rabbits, and more
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It’s a familiar scene: You step outside to look at your garden one sunny morning, and find that your beautiful tomatoes have been gnawed, your broccoli leaves are full of holes, and your seedlings have disappeared altogether.
You’re not alone in your garden. Rabbits, groundhogs, squirrels, chipmunks, and hungry bugs are happy to devour those nice, juicy, tender young young vegetables and delicate flowers.
Here are ways to protect your plants so that you can enjoy them, and not just feed the critters in your hard.
1. Know your enemy
Check your plants at least once a week for damage. Look underneath the leaves, at the stems, at the base of the stem, and at any fruits or vegetables that you’re growing. If you can catch signs of infiltration early, you’ll have a much better chance of saving the rest of your garden.
The University of Florida’s guide to insect pests can help you narrow down the suspects quickly. Finding holes in your leaves? Look for caterpillars. Are the leaves turning yellow or brown? Look for insects that pierce and suck on plants’ leaves, such as aphids, flea beetles, scale insects, spider mites, and whiteflies. Are the leaves “skeletonized,” mostly eaten with a few strips of fiber remaining? Consider caterpillars or leaf miners.
Have you found a bug, and you’re not sure what it is? Check out your local agricultural extension’s website for info about the pests in your region. Northern gardeners can start with the University of Minnesota’s insect ID site, which has plenty of pictures of plant-eating critters sorted by size. You can also take a look at their “What’s wrong with my plant?” page to check if your problem is insect damage or a disease.
If the bites look too big to be caused by a bug, consider a larger animal. When deer stop by, your leaves will look torn and ragged because deer don’t have upper incisors. Rabbits and groundhogs have upper and lower teeth, and make a much cleaner bite.
2. Cover up with cloth or netting
A lot of bugs, animals, and birds can be stopped by putting a cloth or net on top of your crops. The most versatile cover for your crops is floating row cover, a thin fabric usually made of spun polyester or polypropylene. It looks a little like packing material, but it’s highly effective at keeping insects, birds, and bunnies out of your garden patch.
Using floating row cover on low-growing plants like lettuce or spinach is easy. Drape the fabric over your plants—leaving enough slack for the plants to grow and push it up—and secure the edges of the fabric to the ground with rocks, bricks, boards, shovels of dirt, or whatever else you have that’s convenient.
Note that floating row cover also keeps pollinators off, so if you’re growing a fruiting vegetable like tomatoes, peppers, eggplant, or squash, you need to remove the row cover when it starts flowering. It can also retain heat—up to 15 degrees warmer during the day—so be aware that plants like beans, tomatoes, and peppers can start sustaining damage at 90°F.
If you’re growing any kind of fruit on trees (apples, peaches, cherries), bushes (blueberries) canes (raspberries, blackberries), or the ground (strawberries), you are going to attract the attention of your ravenous local bird population. After your fruit plants have flowered, when they have started developing fruit, use bird netting to protect your crop.
Make sure to secure it to the ground, and check your nets often to make sure a desperate bird didn’t find its way inside. A bird’s definition of “ripe” is a lot greener than human standards.
3. Give them a bath
Some of the most common insect pests can be deterred by the common garden hose. Aphids, spider mites, and lace bugs can all be knocked off your plants with a stream of water, and they often don’t return. Make sure you spray the undersides of the leaves as well as the tops. (Insects commonly shelter and lay their eggs on the bottoms of leaves, which is one reason humans don’t see them until after they’ve done significant damage.)
If the bath doesn’t seem to be working, try adding some soap. Insecticidal soap sprays potassium salts of fatty acids, which damage insects’ cell membranes on contact. Insecticidal soap is mostly harmless (unless you’re a soft-bodied insect), but it can cause skin and eye irritation, and it can damage some types of plants, including begonias and cucumbers. Read the manufacturer’s instructions before you apply it. Don’t substitute dish soap, which can dissolve the waxy outer coating of plants’ leaves.
4. Bring in some friends to do your dirty work
For every bug that eats plants, there’s another bug that will return the favor. Ladybugs and lacewings will eat all kinds of soft-bodied insects, including aphids, scale insects, spider mites, and mealybugs.
If you’re dealing with deer, groundhogs, or rabbits, the Michigan State University suggests that even getting a dog can help. The dog’s size doesn’t seem to matter, but the dog has to be outside when the animals are eating at night.
5. Build the right barrier
The best way to keep deer, rabbits, groundhogs, and other four-legged frenemies out of your garden is to build a fence. The type of fence you build will depend on whether you’re worried about deer, which jump, or rabbits and groundhogs, which dig.
White-tailed deer can jump 8 ft., but they can’t jump that high and clear much horizontal distance. The University of Vermont Extension suggests several fencing schemes for discouraging deer: 8 ft. tall; 6 ft. tall and slanting outward at a 45-degree angle; or installing two shorter fences 4 ft. apart.
Cottontail rabbits can jump, but they’re not all that ambitious about digging. A 2-foot-tall fence made of chicken wire or 1-inch mesh should keep them out if you bury 3 to 4 inches of fence below the surface. For jackrabbits, build a 3-foot fence with 4 inches buried.
Groundhogs and woodchucks are energetic garden destroyers. Most experts recommend building a 4-foot fence with another 1 ft. buried underground, and the last 6 inches bent outward parallel to the ground in an L-shape.
If you’re thinking of building fences, take a good look around your yard. Are there places where rabbits or rats would be able to hide or nest? Consider tall grass, weeds, brush, low-growing shrubs, or piles of wood or rocks. Remove the rabbits’ happy place, and the rabbit may decide your yard isn’t worth the bother.
And while not a physical fence, the right materials can also keep slugs at bay. You can catch slugs with a bowl of beer, but throwing out a bowl of dead slugs is an unpleasant task—and a waste of beer. To keep slugs away from your favorite plants, surround them with something that slugs can’t cross.
Diatomaceous earth isn’t a poison per se. It has tiny prickly bits that scrape slugs enough that they stay away, and it makes a slug-proof barrier around plants. Or, consider putting a damp burlap bag or board out in your garden: The slugs will crawl underneath the dark, moist area in the night, and you can dispose of them as you wish.
6. Try natural animal repellents
If you have rabbits, groundhog, deer, or any other herbivore chewing up your yard, and you don’t want to put up a fence, you can try using an animal repellent. Don’t bother with alarms or flashing lights; hungry animals will ignore them once they figure out they’re not harmful.
Most animal repellents are made of a combination of rotten eggs (“putrescent whole egg solids” on the label), garlic, and sometimes capsaicin, the chemical that gives chili peppers their heat. You simply spray the repellent on the leaves you want left alone. It may smell terrible for a few hours, but the aroma slowly dissipates, leaving a scent and taste that only animals can sense.
The main problem with repellents is that it’s extremely hard to find one approved for use on anything you’re planning to eat. You can spray any stem or foliage you won’t eat, but if squirrels have been nibbling your tomatoes, you’re out of luck. Repellents also aren’t very long-lasting. Be prepared to re-apply your repellent after every rainstorm if you want animals to stay away—and be prepared to lock up your dogs if they enjoy sniffing and digging for the sources of strange new odors.
7. Make your garden an unpleasant place to be
Cats can be a nuisance in the garden. They roll on plants, smashing them and breaking the stems, and use fresh-dug soil as an outdoor litter box. You can try keeping cats away with deer and rabbit repellent, or cat and dog repellent (check the label to see if it’s safe to put on plants, especially edible plants). And you can try to put up fencing, especially with loose chicken wire at the top; cats don’t like to climb wobbly things. But what can be really effective is making the ground less attractive to walk on.
Cats love smooth soil and open space. To keep cats away from open soil, make it less comfortable. Put down netting, chicken wire, or mesh, or pine cones. You can put them on the surface of the soil, or bury them under a thin layer of soil if you prefer a more rustic look. When the cat scratches, it will get an unwelcome surprise. Strips of outdoor carpeting can also help.
If you don’t have mesh lying around, you can also stick plastic forks, chopsticks, plant stakes, or other detritus upright in the soil every 8 inches or so, so there aren’t any clear areas for scratching and rolling.
8. If all else fails, use chemical sprays
Nobody wants to spray their garden with poison. If your plants are being devoured by insects, there are some chemical sprays that won’t damage your plants, your pets, your families, or the bees and other pollinators that plants depend on.
Bacillus thuringiensis kurstaki (BTK), commonly sold under the name Thuricide, is a bacteria that attacks caterpillars. It only works if the caterpillar eats it, so you have to spray it on a plant that’s already infested while the caterpillars are still eating it. It’s safe to use near bees and beneficial insects like lacewings. It’s approved for use on organic farms, and it’s considered safe to use on edible crops. Follow the label directions, and remember to reapply it after a rain.
Three other common pesticides — horticultural oil, spinosad, and azadirachtin — are considered safe for humans and most other species, but are toxic to bees. Never spray these chemicals during mid-day hours when bees are out foraging: Spray them at dusk or dawn. Use these substances wisely, and you can protect your garden and the earth.
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