Lacewings feed on garden-munching aphids and mites. (Photo by Thinkstock)
There’s no such thing as a bad bug. When wasps sting, termites tunnel, mosquitoes bite, ticks and fleas spread disease, and aphids make a meal out of the vegetables destined for our own dinner tables, they are simply acting on their instinct for survival. But if that natural behavior runs up against a gardener’s passion, there is only enough room for one of us to be right. So we call them pests.
There is another breed of insect that goes by another name. They prey on pests, parasitize nuisance insects, pollinate fruits and vegetables, and break down dead plant matter to enrich the soil. They earn our esteem by doing what they were born to do. We call them beneficial bugs.
Entomologist Eric Day prefers not to make value judgments about the insects he works with. Manager of the Insect Identification Lab at Virginia Tech in Blacksburg, Day is a gardener himself. “Beneficial insects provide free biological control,” he says. “A beneficial insect is one that causes the mortality of pest infestations and reduces damage to vegetative and ornamental plants.” Call them what you will, they are all part of the biodiversity that keeps the natural world in balance.
Lady beetles feed on aphids, white flies and scales. Predatory mites devour spider mites and other pest mites. Lacewings eat aphids and mites. Parasitic wasps lay eggs on the bodies of their host caterpillars. Spiders prey on a variety of insects. In nature’s equilibrium of competing forces, pests are controlled by their natural predators.
To encourage beneficial insects in your garden, Day recommends treating them to the same hospitality you would any welcome guest. Research their eating and habitat preferences, and then offer the food and comfortable living conditions they prefer.
And be careful to avoid broad-spectrum spraying. Pesticides are not particular; they kill the beneficial bugs in your garden just as effectively as they kill the troublemakers. Even organic pesticides are detrimental. Instead, Day prefers a targeted approach. “Do some research to learn how to control a particular pest,” he recommends. Day offers the following strategies to help control pest damage.
Grow plant species that are native to your region. “Native plants have evolved to be more resistant to native pests,” he points out. It’s the most natural kind of pest control there is.
Promote plant diversity. “Gardens are artificial ecosystems. When we plant multiples of the same species of plant, we create a monoculture,” Day says. A field of corn or a row of tomatoes is a boon to the bugs who thrive on that particular food. “It enables pests to get established and doesn’t support their natural enemies,” he explains.
Take cover. Protect pumpkin, squash, cucumbers and watermelon seedlings from predatory insects with a fabric row cover. Remember to remove it when the plants flower so that pollinators can do their job. Or plant them after June 15, when most pests have moved on.
Keep your garden healthy. The right light, water and nutrition will strengthen its defenses and make it naturally resistant to damage.
Practice tolerance. In his own garden, Day takes a passive approach. He accepts pests as a necessary evil — a food source for the beneficial insects that keep them in check. “I simply tolerate the damage,” he says, “and enjoy my garden. I think of it as the price I pay to bring things into balance.”
