Guide to Organic Pest Control

Enlarge Image Image Gallery One of the not so good bugs, a two-striped grasshopper. DWIGHT KUHN

Sharp-eyed handpicking and trapping can control many garden pests, but not every insect battle can be won with hand-to-hand combat. Instead, you may need an intervention plan that affects the pest, yet causes little or no harm to natural predators and beneficial life-forms that live in your garden. This is where organic pest control products can come to the rescue. To help you match the best products with each pest, we’ve organized our guide in two ways — by pest and by remedy. Read through the Organic Remedies for Garden Pests table and then bring yourself up to date on cures with “Top 11 Organic Pest Control Products” on the next few pages. The information in the table and the text is based on current recommendations from sustainable agricultural research centers throughout North America.

In the last few years, much has been learned about the secret world of garden insects. Spraying is not your only option. Growing flowers to provide nectar and pollen for beneficial insects, and excluding pests with row covers are both remarkably effective preventive measures. You can learn more about these two options by searching for “beneficial insects” and “row covers” on our Web site. And don’t forget our feathered friends — wild birds, ducks and chickens feast on all kinds of garden pests (see “Poultry Pest Patrol”).

Top 11 Organic Pest Control Products

Before you decide to use any organic pest control product, take the time to correctly identify the pest (see “What’s Buggin’ You?” below) and see if it will respond to cultural controls, such as simple handpicking. (Using the wrong product could cost you time and money, and may backfire by killing natural predators.)

The Basic Biologicals. The oldest and best known of biological pesticides is Bt (Bacillus thuringiensis ssp. kurstaki), which remains a top remedy for leaf-eating caterpillars. Bt is based on a naturally occurring soil bacterium that causes the insect’s gut to rupture several hours after it eats it. A newer biological pesticide called spinosad is a fermented brew of two naturally occurring bacteria, and it slowly paralyzes insects after they eat it. Spinosad is widely used in fire ant baits, and it is also useful for controlling leaf-eating beetles, such as Mexican bean beetles and Colorado potato beetles. Where cabbageworms, armyworms, European corn borers or other caterpillars require repeated treatment, experts recommend alternating Bt with spinosad to keep insects from becoming resistant.

Itchy Irritants. Although diatomaceous earth feels as soft as talcum powder in your hand, under a microscope you would see that each particle has sharp edges. When enough gets wedged into the head and leg joints of soft-bodied insects, they dry up and die. Diatomaceous earth deters slug feeding, too. The effects are short-lived because it seeps into mulch and soil after rain, but a thorough, well-timed dusting can still give good control of aphids, leafhoppers, and slugs or snails. In contrast, the particles of kaolin clay are so tiny that they form a thin paint when mixed with water. Leaves covered with the stuff are ignored by many common pests, and those that do nibble on clay-coated leaves usually move on. Organically grown produce that has traces of a dusty off-white residue was probably treated with kaolin clay.