A Lively Alternative to Garden Chemicals
A large, organic garden is thriving in central Minnesota thanks to the tender loving care of dedicated gardeners, and the vigilance of an avian and insect air patrol. Bees, butterflies, birds and parasitic wasps fly randomly looking for a lunch of garden pests, and gardener Mike Chouinard couldn’t be more pleased. "When we have a bug problem, suddenly bees or something will show up and take care of it," says Chouinard. "We like to have beneficial insects and animals around to go through their natural cycle."
Growers like Chouinard who want to avoid or reduce the use of pesticides must find alternative ways to deter or eliminate pests from destroying crops. One technique that organic farmers and gardeners have been experimenting with for years is biological pest control—using beneficial insects, birds and bats to control pests in gardens and on farms. Introducing friendly insects, or building houses for birds and bats, has proven effective, but many warn that biological pest control should be seen as just one part of a gardener’s Integrated Pest Management (IPM) plan.
According to the U.S. Department of Agriculture (USDA) Natural Resource Conservation Service, IPM involves monitoring, determining tolerable injury levels and applying appropriate strategies. By monitoring for damage and differentiating the beneficial insects from the harmful pests, growers can tailor IPM to employ "only those controls that are needed, when they are needed."
Some of the most common pests such as aphids, whiteflies and moths are fairly controllable by introducing beneficial insects such as lacewings, ladybugs and pirate bugs. Supplying these benign bugs can be as easy as stopping at the local garden center. But, warns Chouinard, it’s important to "create a climate for these creatures to stick around." To accomplish this, he plants mullein and Queen Anne’s lace with large, droopy leaves to provide shade for beneficial insects. Dill, parsley, lemon balm and fennel are a few other plants that sustain these helpful bugs.
Foraging While Flying
While beneficial insects tend to be more well-known, other beneficial creatures can be a part of IPM as well, says Phil Radspinner of Peaceful Valley Farm and Garden Supply of Grass Valley, California. Radspinner says that bats eat moths, mosquitoes and beetles, so putting up a bat house can help control these pests. Barn owls attack mice, rabbits and gophers. Birds also patrol for specific pests, and houses varying in size and shape attract different types of birds. For example, studies show that a single purple martin can eat 2,000 flying insects a day.
"Any of these natural controls will work on any scale," says Radspinner. "It doesn’t matter how big your home or garden is, but timing is definitely an issue. You have to plan ahead and anticipate a pest problem." The best time to introduce a predatory species is before pests show up or immediately after they appear. When the insect has reached the point of infestation, it’s too late and predators probably won’t be able to correct the problem.
The alternative—pesticides—are not an option for many people. "If you want to naturally control pests, don’t kill the predators too," says Mark Hostetler, associate professor of wildlife ecology at the University of Florida. "When you wipe out all insects with pesticides, pests are the first to come back. The natural predators take longer to come back," he adds.
Chouinard adds that using chemical pesticides can create a cycle of dependency. "Once you use chemicals," he says, "you need to re-apply again and again." Nobody claims that biological pest control is 100 percent effective, but Hostetler insists that if you can tolerate some loss, it’s possible to use natural predators with no pesticides to maintain flower and vegetable gardens.
There aren’t many drawbacks to introducing beneficial species. Chouinard says that most birds will devour pests, but some birds might also attack fruit and vegetables, particularly berries. Radspinner points out that some people overestimate their need for beneficial insects. "If you overdo it, farmers and growers might find it’s not cost effective," he says. He adds that releasing too many predators will not be damaging, since the excess predators will move on in search of food elsewhere.
Chouinard says his pest solutions continue to evolve. "Every season I have to start over to figure out what’s going to work for my garden this year," he says.
RACHEL ANDERSON is a former E intern.