Put Down the Pesticides! Introduce Beneficial Insects Into Your Garden

There are three major groups of beneficial garden insects — pollinators, insect predators and parasitoids — and they all work in different ways to keep your garden healthy.

Pollinators are insects that move pollen from the male parts of a flower to the female parts of either the same or a different flower. Pollination is essential in the reproduction of angiosperms, or flowering plants, which represent around 80 percent of all plants living today, including all the vegetables in your garden. Around 200,000 different animals pollinate flowering plants, but the vast majority of these are insects — butterflies, moths, flies, ants, beetles, bees and wasps.

Insect predators are pest eaters — they are attracted to the undesirable insects as a food source. Which predators will keep the pests in your garden in check depends heavily on which pest you have and what you're growing. Steve O'Shea, owner of 3 Porch Farm, a flower farm in Comer, Georgia, purchases predaceous insects to keep local pests in check.

"We use two types of predatory mite and one called the minute pirate bug, which target the early developmental phases of western flower thrips, which used to be a major problem for our dahlias," says O'Shea. "Beneficial insects are expensive, but in our experience, they actually work better than sprays. They don't eliminate every thrip, but they do an amazing job of controlling their numbers so the population never gets large enough to do significant damage."

Parasitoids are different from parasites. While a parasite can live off its host, they don't necessarily have to kill it in order to survive, but parasitoids kill their host as a means of completing their life cycle. Parasitoid insects lay eggs inside or on top of their host — generally they use one very specific species as their host — and when the eggs hatch, the larvae use the host as a food source, killing the host in the process.

Beneficials insects can be purchased, varying in price depending on type and provider, or you can attract them to your plot. In fact, unless you're using broad-spectrum pesticides, there are probably a lot more beneficial insects in your garden than you realize.

Beneficial insects like ladybugs, praying mantises, parasitic wasps and ground beetles will be attracted to your garden based on what you plant — they're especially attracted to members of the carrot family like carrots and Queen Anne's lace, asters like sunflowers, marigolds and coneflower, as well as legumes and mustards.

Insects also need a source of water — they especially like shallow dishes filled with pebbles to rest upon.

Beneficial insects are great, but they can't do everything, so it's likely you'll want to use them in conjunction with some sort of insecticide which will likely also kill the beneficials in your garden. Most pests you try to control are less sensitive to insecticides than beneficials, so it's important to choose insecticides that don't hang around for a long time after they're applied. Synthetic insecticides tend to linger for longer, so things like insecticidal soap, horticultural oil and botanical insecticides like rotenone, sabadilla, neem and pyrethrins are better choices.

According to O'Shea, in planting a garden — or in his case, acres of delicious flowers — we unintentionally create a great source of food and habitat for pests. It makes sense that their populations explode and they demolish everything when faced with a bunch of tender little horticultural plants.

"By increasing the beneficial insect populations, we preemptively address and counter that ecosystem imbalance that our crops alone would encourage," says O'Shea.

He also says that using beneficials might not be for everyone. For instance, the cost of buying beneficials might be too high for some home gardeners.

"Using beneficials does not work in every situation," says O'Shea. "Consult the experts, make your best efforts and observe your results to see if it's the right approach for you going forward."