14 Nontoxic Ways To Keep Pests Out

Organic insect control starts with a prevention plan.

July 14, 2015
no trespassing
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PHOTOGRAPH BY KARAGRUBIS/GETTY

 

Sensible organic practices allow vegetable gardeners to sidestep many insect pests—and avoid the more difficult task of eliminating pests after they’ve settled in. First, the basics: Give plants optimal growing conditions to keep them healthy. Plants that are stressed—by drought, for example—give off signals that draw pests to them. Monitoring crops regularly lets you deal with problems before pest populations multiply. Organic sprays are a last resort to be used with caution; some can kill beneficial insects as well as pests.

aphids
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Aphid

PHOTOGRAPH BY BILL JOHNSON

 

Tiny, sap-sucking insects feed on many kinds of plants throughout the growing season.

 

Related: Make Your Own Natural Pest Spray

 

Defensive Strategies

Provide food for aphid predators by mixing small-flowered plants like mints or yarrow throughout your garden. Avoid overfertilizing with nitrogen; the resulting lush, juicy shoots are aphid magnets.

 

Organic Control

Crush aphids with your fingers or knock them from plants with a strong spray of water. Treat persistent infestations with an insecticidal soap spray, such as Safer Insect Killing Soap.

carrot rust fly
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Carrot Rust Fly

PHOTOGRAPH BY WHITNEY CRANSHAW/COLORADO STATE UNIVERSITY/BUGWOOD.ORG

 

Larvae of small, metallic green flies eat root hairs and tunnel into roots, stunting growth.

 

Defensive Strategies

Rotate carrots, planting them in a different garden location every year. Delay sowing until June to miss the early-spring egg laying of rust flies. Protect seedbeds with floating row cover.

 

Organic Controls

Damage is typically unseen until it's too late. Be wary of stunted, sickly topgrowth; pull and destroy infested crops. Remove crop debris at the end of the season.

colorado potato beetle
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Colorado Potato Beetle

PHOTOGRAPH BY BILL JOHNSON

 

Striped adults and humpbacked orange grubs feed on potato leaves and stems.

 

Defensive Strategies

Rotate potatoes. Cultivate beds in fall to expose and destroy overwintering adults. Apply straw mulch 4 to 6 inches deep around plants. Plant early-maturing varieties to avoid peak damage.

 

Organic Controls

Handpick slow-moving adults and larvae and drop them into soapy water. Seek and destroy orange-yellow eggs on leaf undersides. Spray with spinosad, such as Entrust SC.

cutworm
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Cutworm

PHOTOGRAPH BY BILL JOHNSON

 

Gray-brown caterpillars feed nocturnally on seedlings, severing stems at soil level. 

 

Defensive Strategies

Turn the soil a few days before planting to expose cutworms. Surround the stem of each transplant with a ring of rigid paper or cardboard, 4 inches tall, pressed 2 inches into the soil.

 

Organic Controls

Prepare a bait of bran moistened with Bacillus thuringiensis var. kurstaki and molasses, and sprinkle it over beds a week before planting. Dig next to cut seedlings to find the perpetrator.

imported cabbageworm
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Imported Cabbageworm

PHOTOGRAPH BY ANSEL OOMMEN/BUGWOOD.ORG

 

Green, inch-long caterpillars riddle the leaves of brassicas with holes.

 

Defensive Strategies

Put floating row cover—ultra-lightweight, sun- and water-permeable fabric—over cole crop transplants immediately after planting and keep it in place until harvest.

 

Organic Controls

Destroy eggs on leaf undersides. Handpick caterpillars. Remove severely infested plants. Spray with Bacillus thuringiensis (var. kurstaki or aizawai), such as DiPel DF; or spinosad.

mexican bean beetle
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Mexican Bean Beetle

PHOTOGRAPH BY MARK MOFFETT/GETTY

 

Adults and spiny yellow grubs munch bean pods and skeletonize leaves.

 

Defensive Strategies

Plant early bush bean varieties. Interplant beans with flowers and herbs to support native predators. Use floating row cover over young plants to exclude egg-laying adults.

 

Organic Controls

Sow an early patch of soybeans as a trap crop to lure the pests. Destroy yellow eggs on leaf undersides. Handpick adults and larvae. Spray with neem, such as Biosafe Insect Control.

squash bug
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Squash Bug

PHOTOGRAPH BY BILL JOHNSON

 

Adults and nymphs suck juices of vine crops, especially winter squash.

 

Defensive Strategies

Choose varieties that are tolerant of squash bugs. Shield young plants with floating row cover; uncover when blossoms open. Raise vines on trellises.

 

Organic Controls

Place boards on the ground near squash plants; in the morning, destroy pests underneath them. Handpick adults and nymphs. Crush eggs on leaf undersides.

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