Companion Planting for Pest Control
Companion planting can be a highly effective means to repel plant pests and attract pests’ natural enemies or parasites. Many common benefits of companion planting are: masking or hiding a crop from pests, producing odors that confuse and deter pests, serving as trap crops that draw pest insects away from other plants, acting as “nurse plants” that provide breeding grounds for beneficial insects, providing food to sustain beneficial insects as they search for pests, creating a habitat for beneficial insects.
Marigold is an annual flower that has a distinctive smell which deters many garden pests. To achieve the maximum benefit, you should plant marigold throughout your vegetable rows. The French Brocade Marigold has the added benefit of nematode control as its roots emit a substance that repels nematodes in the immediate area. For marigolds to be effective in nematode control, they should be grown over at least one full season and additional seasons for their effect is cumulative.
Rue is a shrubby perennial herb that has uniquely fragrant, blue-green leaves and 2-inch yellow flowers that make it attractive in borders. Used as an old European culinary and medicinal plant, this herb, when planted near roses and raspberries, deters Japanese beetle. Sow rue seeds along the vegetable and flower garden borders or scatter rue leaf clippings in an infested area. Rue can cause a poison ivy-like rash for some people, so handle rue with caution by wearing long sleeves and gloves.
Sweet Basil is a popular kitchen herb but when grown among vegetables or flowers it repels aphids, mites, and mosquitoes.
The companion charts below are great references for what to grow to deter pests and to attract beneficial insects.
| COMPANION PLANTING TO DETER PESTS | |
| PEST | WHAT TO GROW |
| Ant | Pennyroyal, Spearmint, Tansy |
| Aphid | Larkspur |
| Borer | Garlic, Nasturtiums, Tansy, Onion |
| Cabbageworm | Geranium |
| Cucumber Beetle | Tansy |
| Cutworm | Tansy |
| Flea Beetle | Wormwood, Mint, Catnip |
| Gopher | Castor bean |
| Japanese Beetle | Garlic, Larkspur, Tansy, Rue, Red buckeye, Four-o’clocks |
| Leafhopper | Petunia, Geranium |
| Mexican Bean Beetle | Marigold, Rosemary, Summer Savory, Petunia |
| Mouse | Mint |
| Mole | Spurge, Castor Bean, Mole Plant, Squill |
| Nematode | Marigold (either African or French), Salvia, Dahlia, Calendula, Crotalaria |
| Plum Curculio | Garlic |
| Rabbit | Allium, Dusty Miller |
| Rose Chafer | Onion, Geranium, Petunia |
| Slug/Snail | Prostrate Rosemary, Wormwood |
| Squash Bug | Tansy, Nasturtium |
| Striped Pumpkin Beetle | Nasturtium |
| Thrip | Larkspur |
| Tomato Hornworm | Borage, Marigold, Opal Basil |
| Whitefly | Nasturtium, Marigold, Nicandra (Peruvian ground cherry) |
| Wireworm | White Mustard, Buckwheat, Woad |
| COMPANION PLANTING TO ATTRACT BENEFICIAL INSECTS | |
| PLANT | BENEFICIAL INSECTS THEY ATTRACT |
| Achillea spp. (yarrow) | Bees, Parasitic Wasps, Hover Flies |
| Angelica archangelica (angelica) | Lady Beetle, Lacewings |
| Iberis spp. (candytuft) | Syrphid Flies |
| Ipomoea purpurea (morning glory) | Lady Beetle |
| Nemophila menziesii (baby-blue-eyes) | Syrphid Flies |
| Oenotheru biennis (evening primrose) | Ground Beetle |
| Solidago spp. (goldenrod) | Lady Beetle, Predaceous Beetle, Parasitic Wasp |
Organic pesticides should be used only as a last resort and in the smallest quantities possible so to minimize the harm they do to butterflies, bees, and other beneficial insects. Keep in mind that all pesticides, even organic ones, leave some toxic residue that will remain in your garden for years.
**Information sources used here:
Carrots Love Tomatoes, by Louise Riotte
Roses Love Garlic, by Louise Riotte
All-New Encyclopedia of Organic Gardening, Rodale Press (editor)
