Select Pest Hardy Plants--cultivars of corn that have good thick husks are seldom much bothered by corn earworms. And purple cabbage is seldom troubled by imported cabbageworms. Many varieties of tomatoes and other vegetables are bred for natural resistance to disease.
Concealing or Masking the crop from pests--light weight, translucent row covers are a good way to prevent many pests from getting into your young crops while still allowing sunlight, water, and air to circulate. This technique is particularly good for the young, tender salad crops--lettuces, cabbages, spinach, kale.
Producing odors that repel or confuse a bug--scientific experiments have demonstrated that many of the night-flying moths, including the one that delivers those vicious cut worms to your garden, track odors upwind to the plants they lay their eggs on. Marigolds (most nursery marigolds are unscented so look for Tagetes patula or Tagetes erecta -- if anybody runs across these spp. locally, let me know) mints, and sweet basil interplanted with flowers and vegetables helps to "mask" or repel unwanted pests.
Use a "Trap Crop" to lure unwanted insects away from your garden--growing collards well away from cabbage will help protect against diamondback moth larvae. Plant petunias well away from your roses to trap Japanese Beetles. And be sure to remove and replace any infested "trap" crops to keep the pests from multiplying and spreading to your more desirable plants.
Provide food for beneficial insects as they search for pests--beneficial insects tend to have short mouth parts. So small, open faced flowers will provide easy to reach pollen and nectar to give your little garden friends the strength to go after the pests. Dill, fennel, anise, and coriander (all members of the carrot family) produce small flowers suitable for beneficial insects. Longer blooming sunflowers, zinnias, and asters also attract and feed them. Other plants attractive to beneficial are yarrows, angelica, chamomile, candytufts, morning glory, baby blue eyes, evening primrose and goldenrod. You'll notice that many of these plantings are basic to a butterfly garden.
Companion Planting--There are some winning combinations for companion planting:
- Basil and onions with tomatoes to control tomato hornworms.
- Thyme or tomatoes with cabbage to take care of flea beetles, cabbage maggots, and white cabbage butterflies
- Catnip with eggplant to deter flea beetles
- Set Onions in rows with carrots to control rust flies and nematodes.
- Horseradish with potatoes to repel the Colorado potato beetle
- Add radishes or nasturtiums near your cucumber plants to control cucumber beetle
- Interplant borage among your tomatoes, cucumbers, and strawberries to both repel some pests and attract many good ones
- Cilantro among the spinach will repel aphids and attract the very beneficial tachinid flies
- Summer Savory with your beans will repel bean beetles
- grow tomatoes, parsley, or basil with your asparagus to help keep a check on asparagus beetles
- and if you can, leave the paper wasps nests and spider webs alone. They are ferocious hunters.
And don't forget the beneficial animals --Toads for instance, eat 3,000 grubs, slugs, cutworms, flies, wood lice, grasshoppers and beetles a month (make a toad house by placing an old clay pot upside down in a cool, moist, out-of-the-way place in your garden. Break out a door for Mr. Toad, about the size of a 50 cent piece, at the rim where the pot touches the earth). An added benefit of toads is they won't turn on your flowers and vegetables if there are no insects to eat. Most pests are actually night workers, so a single bat will eat 1,000 bugs a night, a family of bats thousands. If you're near some open spaces,consider erecting a purple martin house, each martin eats 1,000 insects in 12 hours. A single wren can gobble down 500 insect eggs, beetles and grubs an afternoon. 60% of a chickadees diet during the winter is comprised of aphid eggs.
All good reasons to make your yard as bird and animal friendly as possible.