Control Garden Pests

In part three of our four-part gardening series, we deal with the pests that want to dine on your produce.

Summer’s finally here, and your vegetable garden should be lush and productive. But wait! What are those holes in the kale leaves? And weren’t there baby lettuces here last night?

Welcome to the organic garden, where your fabulous food crops aren’t only on your radar. A whole army of critters—from microscopic soil pests to flying, slithering, and crawling brigades of aphids, beetles, leaf miners, and slugs—have their sights on your produce too.

There’s nothing more discouraging to the new vegetable gardener than to see healthy, beautiful plants stripped of foliage and squirming with unappetizing aphids, or carrots laced with yucky tracks and tunnels made by carrot rust fly larvae.

Do nothing extreme

Get out the organic dusts and sprays? Not necessarily, most long-time organic gardeners will tell you. The best tack is to do nothing extreme, as even natural insecticides and sprays can upset the balance in your garden by killing both bad and good insects.

That’s because the bad bugs are often a food source for good bugs; the best scenario is to find a balance between the two. You may lose a few plants, but damage will be minimal because the destructive pests will have been eaten by the good guys. Besides, says gardening expert and columnist Anne Marrison, “I don’t like to eat food that’s been sprayed with anything.”

Successful gardening requires experience. You’ll learn which pests want to undo your work and when they’re most prominent. Make note of this, and time your planting to avoid the worst periods of infestation.

One heartening thing to remember is that healthy plants are less likely to be attacked by pests. If a particular plant has been badly damaged, remove it, and destroy it immediately, Marrison suggests. The rest of your crop will still be top quality.

Know thy enemy

The reality is that insects inhabit every nook and cranny of our environment, and it’s folly to think they can ever be completely controlled. So the best thing to do is to learn what they like to eat, where they live, how they develop, and at what stage they do the most damage.

Many garden pests develop through several stages from eggs to larvae (caterpillar, worm, or nymph stage) to adult (moth, beetle, et cetera), and you need to identify which stage poses a threat to your crops. Those pretty little white butterflies that flit through the kale and cabbage don’t do any damage at that stage. But the eggs they are busy laying on your cabbages will hatch into little green worms with voracious appetites (see end of article).

Companion planting

Marrison says she’s had problems with the carrot rust fly. Last year she threw a handful of carrot seeds in amongst her garlic plants. The result? No rust fly damage. This is called companion planting. Many strong-smelling plants, such as herbs and flowers, will throw off a pest’s sensitive smell receptors.

Crop rotation

Another key practice to incorporate into your gardening plan is crop rotation, says Marrison. Bugs get comfortable and don’t want to move. So planting the same crop in the same space year after year is like opening a 24-hour restaurant for them. By moving your beans, beets, or carrots at least 30 feet from where they are this year, “pests will have to work for what they get,” says Marrison.

The bottom line is this: encourage balance by allowing the good bugs—spiders, ladybugs, predator wasps, lacewings, assassin bugs—to take care of the bad guys, practise crop rotation, and keep your garden beds clean so pests won’t overwinter. It’s a sure recipe for successful organic gardening.

Natural bug zappers

Organic insecticides, such as pyrethrum, rotenone, and sabadilla, are broad-spectrum killers, meaning they destroy both good and bad bugs. Garlic, onions, hot peppers, rhubarb leaves, strongly scented herbs such as mint, and even orange peels can be used as more benign bug sprays and deterrents.

Some of these substances—rhubarb leaves specifically—are toxic to humans, while hot peppers can irritate skin and eyes, so use caution in preparing and applying such mixtures.

All-purpose bug spray
Use this liquid as a spray to kill bugs on vegetables, roses, and azaleas.

In a blender combine 3 whole cayenne peppers, 1 large onion, and 1 bulb of garlic with 1/4 cup (60 mL) water. Cover mixture with 1 gallon (4.5 L) water. Let stand for 24 hours, then strain. Spray plants to control bugs; bury the pulp among the plants where infestation occurs.

—Source: CEED Centre Society

Common garden pests

Although most bugs are beneficial to your garden, the few that do cause destruction can seem daunting. Here are some of the most common pests.

Aphids
These soft-bodied creatures attack most vegetables and come in a host of colours from black to yellow, green, purple, and pink. Aphids reproduce rapidly and can weaken or destroy a plant if not kept in check.
What to do: A strong spray of water can usually dislodge them, but if the infestation is serious, a natural insecticidal soap (commercial or homemade) will do them in.

Beetles
Cucumber beetles also attack melons and squash. Colorado potato beetles love tomatoes, eggplant, and peppers, and Mexican bean beetles like cabbage, kale, collards, and mustard greens. There are also various species of tiny flea beetles that attack young tomatoes, eggplant, spinach, beets, radishes, and turnips.
What to do: Row covers can help keep these pests away from your plants. Hand-picking can also reduce their impact.

Slugs and snails
Slugs and snails do their damage at night, preferring to hide out in cool damp places during the day.
What to do: If there’s a bad infestation, head out at dusk with a flashlight and pick them up by hand, dropping them into a bucket of soapy water as you go. Slug and snail bait is effective too, but make sure it’s a variety that’s nontoxic to pets and people.

Caterpillars
Butterflies and moths are the final stage in a life cycle that includes being a caterpillar. Most caterpillars prefer specific wild plants, but a few can cause serious damage to food crops, including the tomato hornworm, cabbage worms, loopers, and corn earworms.
What to do: Each has its predator in the well-balanced garden, so avoid using any broad-spectrum insecticides to eradicate them because these kill good bugs too. Hand-picking is safer than using insecticides.

Cutworms
These pests do their damage underground. Cutworms are the caterpillar stage of different varieties of moths, and those destructive to your garden will feed on a wide variety of young vegetable plants, usually at night. Once the cutworms move onto their next stage of development (moths), they’ll lose interest in your plants.
What to do: Plant collars made of cardboard (use toilet paper or paper towel rolls) pushed several inches into the soil around each plant will usually keep cutworms and wireworms at bay.

Wireworms
Wireworms are the larval stage of the click beetle, and though they prefer eating the roots of grassy plants—hence their presence in garden beds that were recently lawns—they’ll go after any plant available.
What to do: See cutworms above.