Organic Pest Control Strategies for the Garden

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An American toad eyes a potato beetle.
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In their larval stage, lacewings help prevent aphid outbreaks.
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As adults, lacewings feed on flower nectar.
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This fierce-looking critter, which is eating aphids, is the larval stage of the familiar ladybeetle.
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A young duck prepares to gobble up a slug.
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Wasps are an excellent ally against garden pests. Many help control common caterpillar pests.
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Some wasps lay eggs in aphids, thereby killing them.
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From left to right: Pest Pistol; Dustin-Mizer; Solo 2-liter sprayer. All products are available from Peaceful Valley Farm and Garden Supply.
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Squash Bug
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Adult Bean Beetle
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Larval Bean Beetle
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Flea Beetle
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According to an ancient Chinese proverb, “If you would be happy all your life, plant a garden.” Modern gardeners know this to be true, but unfortunately our gardens also seem to inspire delight in grasshoppers, squash bugs and countless other hungry insects. There’s at least one serious insect enemy for every crop, so knowing how to prevent and treat pest problems is fundamental to maximizing the rewards you can reap from your gardening efforts.

When faced with a pest problem, gardeners — new ones in particular — often reach for a solution that comes in a spray bottle. It’s true that many poisons sold in garden centers will kill any, and often all, insects in your garden. (Some of these products are less toxic than others, see Top Organic Pest Control Products for options approved for organic growers.) But spraying chemicals is rarely the best option for getting rid of pests. Many pesticides are hazardous to humans and wildlife, and most will kill beneficial insects right along with the pests you’re targeting.

Organic Pest Control Strategies

Before you march into your garden armed for an insect Armageddon, answer these three important questions:

  1. Are there natural predators capable of controlling this pest? In many cases the answer is yes, but you will never see your garden’s homeland defenses in action unless you actively encourage beneficial insects (see Image Gallery) and adopt a wait-and-see attitude when new pest problems arise. Always watch what happens for at least five days after you see a pest become active. This can be a wonderfully fascinating show. To encourage natural predators, provide food and habitat — for more information, see Protect Your Garden with Beneficial Bugs.
  2. Can you control this pest by using preventive methods? You can prevent attacks from many nonflying insects — as well as diseases — by rotating your crops (not planting them in the same place more than once every three years); by cleaning up and composting dead plants; by eliminating habitats such as weedy host plants; or by growing resistant varieties. Learning to use methods that prevent pest problems does not happen overnight, and even the most experienced organic gardeners pick up new strategies with each passing season. When it comes to learning what works and what doesn’t, your garden often is your best teacher. The books and Web sites listed under “Sources” later in this article also provide excellent advice.
  3. Are there easy ways to capture the pest or to install barriers that will protect the plants? Some insects are easy to pick off and drown in a pail of soapy water, or perhaps you can nab them with pieces of duct tape or a rechargeable vacuum. If you see a certain pest returning to your garden year after year, you often can keep the hordes at bay by covering plants with lightweight floating row covers.

All of the possible answers to these three questions are called cultural controls, which can be remarkably effective. When Cornell University brought together five horticulture experts to summarize the effectiveness of organic pest-control options for 36 vegetable insect pests and diseases, they found that 20 often could be handled using cultural controls. In your garden, the ratio between problem pests and cultural solutions can get tighter as you learn to make use of practical preventive measures.

Know Thy Enemies: Identify Common Garden Pests

It’s important to understand that most garden pests are only capable of damaging a very narrow range of closely related plants. For example, little black flea beetles may make holes in potato leaves in spring, then hop to tomatoes or eggplant in summer, but they won’t veer far from plants that are members of the nightshade family. In similar fashion, the squash bugs that invade your pumpkin patch cannot digest juices sucked from lettuce or broccoli. A few pests do have broad feeding ranges (Japanese beetles eat the leaves and flowers of more than 200 plants, and some grasshopper species have equally varied tastes), but for the most part, garden pests require the presence of specific host plants — that’s where you can target your efforts.

It’s wise to learn as much as you can about the life cycles and physiques of the pests that are damaging plants in your garden. Invest in a hand-held magnifying glass and a good insect identification book, such as Garden Insects of North America: The Ultimate Guide by Whitney Cranshaw. Also bookmark useful online resources. Two excellent places to start are Cornell University’s Resource Guide for Organic Insect and Disease Management and the University of California’s Integrated Pest Management Program.

To find local information, begin with the U.S. Department of Agriculture’s guide to regional integrated pest management centers. The Ontario Ministry of Agriculture, Food and Rural Affairs is bursting with good information on insect identification and control.

The more you know about your problem pests, the better job you can do choosing an intervention that will prevent or stop the damage without sabotaging the important work done by beneficial life-forms. Before you get excited about any pest control product, read that last phrase again and consider this story: Last summer, out of the blue, thousands of aphids appeared on my eggplants. Three days later, ladybeetles arrived and began eating the aphids and laying clusters of orange eggs on the undersides of leaves. As I anxiously waited for the eggs to hatch, I examined a few leaf samples with my 20x microscope. Two other beneficials — predatory mite larvae and syrphid fly larvae — had beaten the ladybeetles to the punch. Within a week, the aphids were gone. If I had sprayed those aphids with insecticidal soap, I would have wiped out the food supply for three major predators. It was a lesson I will not soon forget.

Approved Products for Organic Pest Control

If you do decide it’s time to spray, Top Organic Pest Control Products outlines your best options. Every product listed there poses minimal harm to organisms you don’t want to target, including humans. These products also are accepted under the National Organic Program Standards, which serves as a framework for certified-organic food production. But in a world where new “natural” products appear on store shelves every day, there needed to be a way to evaluate whether or not specific products comply with those standards. This is now the job of the nonprofit Organic Materials Review Institute (OMRI). OMRI uses a panel of experts that includes farmers, scientists, environmentalists and businesspeople to decide which products should be approved for use by organic growers. Approved products usually display the OMRI seal on their label, or you can check the OMRI website to see if a product is approved.

OMRI has two category codes for approved products: “A” for allowed and “R” for restricted. Allowed products may be used freely at the grower’s discretion; most of them are soil amendments and organic fertilizers. Many organic pesticides carry a restricted code because they can harm beneficial insects and other wildlife, and thus should be used sparingly. Although all of the products listed in Top Organic Pest Control Products carry OMRI approval, many fall into the restricted category and should be used only when cultural controls have failed, and always according to label directions.

Small Sprayers and Little Dusters

A sprayer is useful for applying pest control products and liquid fertilizers, as well as for other garden tasks such as misting cuttings. Instead of struggling with a cheap pump-spray bottle or a big tank-sprayer, try one of the smaller pressurized sprayers. The Solo 2-liter sprayer shown in the Image Gallery ($19.95) features a nifty nozzle that extends to 20 inches and swivels to direct the spray underneath leaves.

When applying dusts, such as Bacillus thuringiensis (Bt) or diatomaceous earth, always wear a dust mask. For small jobs, the plastic squeeze-action Pest Pistol ($7.95; shown with red lid in Image Gallery) works fine. For larger gardens, the yellow hand-crank Dustin-Mizer ($27.95) is the tool of choice.

The Solo sprayer and the dusters are available from Peaceful Valley Farm and Garden Supply.

Organic Pest Control Sources

Though increasingly available in mainstream stores, organic products can be tough to spot in the midst of the numerous toxic synthetic pesticides that line the shelves of garden centers. Often your best bet is to use one of the mail-order companies listed below — their catalogs are free, and they offer full lines of organic products. Your best buy always is the concentrates, rather than the pre-mixed “ready to use” products. We compared prices for several of the most popular organic products and listed them below.

Peaceful Valley Farm and Garden Supply
P.O. Box 2209
Grass Valley, CA  95945
(888) 784-1722
Bt, 8 oz., $9.49; Insect Soap, 16 oz., $7.50; Neem, 16 oz., $10.95

Planet Natural
1612 Gold Ave.
Bozeman, MT  59715
(800) 289-6656
Bt, 8 oz., $10.95; Insect Soap, 16 oz., $9.95; Neem, 16 oz., $12.95

Worm’s Way
7850 North State Road
Bloomington, IN  47404
(800) 274-9676
Bt, 8 oz., $11.95; Insect Soap, 16 oz., $11.95; Neem, 16 oz., $14.95

Contributing editor Barbara Pleasant gardens in southwest Virginia, where she grows vegetables, herbs, fruits, flowers and a few lucky chickens. Contact Barbara by visiting her website or finding her on .