Battling the Bad Bugs: How to Get Ahead of Garden Pests

As the garden finally moves into the height of growing season, the pest pressure increases exponentially. Put down the bug spray, and read on.

Tomato hornworms are voracious eaters and can quickly defoliate tomato plants and other plants in the nightshade family. Melissa Tate/Shutterstock

The first step in any pest management strategy is to step back and assess the situation. If it’s just a few bad bugs, and the garden is in robust health with a diverse ecosystem, chances are the good bugs will soon take care of them. In fact, it’s a good idea to leave a few pests in the garden to keep the good guys fed.

If, however, the garden world’s first responders don’t take care of the task, it’s time to intervene in as nonintrusive a way as possible, starting with nonchemical methods that keep pest populations down. Several larger pests can be simply picked off by hand, particularly when they first arrive. Bug sprays and powders, even organic ones, should be used sparingly, applied only to affected plants in the evening when the pollinators are done for the day, and never sprayed directly on open or ready-to-open flowers.

The most important thing to take away from this article is this: No garden can be completely pest-free. The trick is to know which ones to remove.

Pull On the Garden Gloves

Being a great gardener is not for the squeamish, particularly when it comes to slugs, hornworms, and cabbage loopers (cabbage worms). Go into the garden around 10 p.m. to look for them.

For slugs, pick them up with an old spoon, and drop them into a container of soapy water to kill them. Three or four nights should be enough to reduce potential damage. For faster results, put stale beer in a bowl dug into the soil (so they can slither right in). They will fall in and drown. Sawdust, garden lime, or diatomaceous earth will create a handy barrier around plants but must be replaced after every rain.

Big, green, and ugly tomato hornworms are often camouflaged by the plant’s leaves. Use a flashlight to make them somewhat luminescent and easier to spot. But if the hornworm has tiny white cocoons covering its body, leave it be; these contain beneficial parasitic wasp babies that will soon feast on the hornworm.

Dill planted next to tomatoes will work as a trap crop, so you can simply pick the hornworms off the dill. Or, if the worms are tiny (less than a half-inch), spray them with the beneficial bacteria Bacillus thuringiensis (Bt).

Cabbage loopers unfortunately do not glow in black light, so leaves will have to be turned over and checked with a flashlight to find them, but the same treatments will be effective.

Bad Beetles

If you see holes chewed in plants leaves, it’s the first sign of asparagus beetles, cucumber beetles, Colorado potato beetles, Mexican bean beetles, flea beetles, squash bugs, or the dreaded Japanese beetles. They also can feed on roots and ultimately kill plants.

The first step is to pick off as many as possible. The adults are usually easy to spot, with their colorful oval or round hard-shell bodies, small heads, six legs, and a pair of antennae.

Japanese beetles feed on more than 300 species of plants. Conrad Barrington/Shutterstock

Shake the plants to make the bugs fall off, then drop them into a container of soapy water. Repeat every few days as needed. Insecticidal soaps like Dr. Bronner’s can be sprayed directly on the bugs to kill them without harming the plants. Be sure not to spray it on any beneficial bugs nearby. Pheromone beetle traps work well to catch males and decimate their reproductive cycle.

Note that there are beneficial beetles as well: ground beetles, which are normally darker in color and have legs that resemble a daddy longlegs spider, and ladybugs, which come in a variety of colors, in addition to their famous red.

Aphids, Whiteflies, and Spider Mites

Tiny green, white, yellow, red, brown, black, and mottled aphids may arrive in a garden all on their own, or ants might bring them in to be “farmed.” As aphids suck the sap from plants, they secrete a honeydew-like substance that ants love. In fact, the ants stroke the aphids’ abdomens as a form of milking them, and they protect them from their other natural predators.

Aphids reproduce rapidly and can have multiple generations in a single growing season, making it especially important to address them quickly. JulieK2/Shuttestock

A strong blast of a hose will knock aphids loose, damaging their fragile exoskeleton in the process. They can also be hand-removed or sprayed with insecticidal soap. As they are known to transmit plant diseases, fully infested plants should be destroyed.

Even smaller white-winged whiteflies arrive en masse to infect plants with diseases, which results in a sooty mold. A vigorous blast with the hose will usually get rid of them. They reproduce (lay eggs) rapidly, so hosing daily may be necessary. For stubborn situations, use an insecticidal soap.

While most spiders in the garden are good guys happily dining on pests, spider mites literally suck the life out of plants, and have been known to use their teeth on humans, too. Spray the undersides of leaves with a hose or wipe them down with a solution of insecticidal soap in water to eliminate these pests.

Inspect plants regularly to catch potential problems early.

Under the Soil

Like criminals who prefer to work at night, some pests work hidden under the cover of soil for subterranean attacks. Don’t let them win.

Contemptible Cutworms

To prevent cutworms from cutting off seedlings at their stem, place a sleeve made from a paper towel roll, a paper cup, or a half-gallon milk carton around the plant, pressing it at least one inch into the soil. Leave two inches above the ground to form a protective fortress.

Wayward White Grubs

In the larval stage of several beetle species, white grubs can be voracious eaters and they love plant roots. Ordering beneficial nematodes is the most natural control. For a faster solution, spray the soil with three tablespoons of Dr. Bronner’s in a gallon of water.

Worrisome Wireworms

While crop rotation is the ultimate solution for these resilient click beetle larvae, beneficial nematodes will address an existing problem. Or cut a potato in half and bury it in the garden one inch deep. Pull it out in a day or two, along with the feasting wireworms.