Healthy soil system may or may not 'deter' pest insects, however, your plants may be better able to tolerate normal infestations. A healthy soil system will be alive with a wide variety of creatures, some of which will help you maintain 'control' over the pests.

It is also very important that you know which of your garden plants are prone to certain disease or insect problems. The healthiest and most balanced of soil systems is not likely to prevent a susceptible variety of rose (just for example) from black spot or aphids. Or hornworms from tomatoes, peppers, and eggplants. ;-)

Knowledge about your specific plants, their ideal growing conditions, and any known susceptibilities is important. That knowledge, along with your understanding of what it takes to build a healthy soil environment, is what makes organic gardening successful. You can have a perfect soil, but still be over-burdened with pest problems if the cultural conditions are all wrong, or you've selected a highly disease or insect prone plant for your garden.

For instance, plants that are either under or over fertilized are more likely to be inviting to pest insects, many of which (but not all) tend to be somewhat opportunistic.

Pest identification is important and there are forums right here in the gardenweb where you can post pictures or just give good verbal descriptions. We will help identify a suspected culprit for you, and make helpful recommendations for prevention and control.

Flea beetles are a terrible nuisance to my eggplant. I do not grow them next to each other to the buggers can't leap from plant to plant. If you have already planted them next to each other, plant radishes in between--they grow fast and attract the flea beetles as a trap crop.

You should also use Milky Spore to deter Japanese beetles (if you have them).

Hot pepper spray mixed with a small amount of dish soap will deter pests--don't apply in the AM when the bees are around as it is toxic to bees.

Put out a bird feeder and next March put up a couple of Purple Martin houses--you will get bug eating birds to move in and help your garden. Preying mantis and ladybugs (both commercially available) will eat bad bugs too.

Over time, the predators to your pests will arrive naturally and eat them, however, the first year will not be easy. No matter how good my soil is--I will never be free of the flea beetles.

Be aware that a lot of injured plants put out a chemical signal to attract predators. That means be careful with even an organic broad spectrum killer like pepper spray. You may kill your helpers. The first step, though, is to identify what's bugging your plants.

tj

While you are working on making your soil good and healthy you need to be proactive about any pests that might show up. That might mean putting in floating row covers, that might mean spraying with a deterent such as a garlic, onion, hot pepper mixture, that might mean interplanting to confuse any pests that may appear, and that also doing eveything you can do encourage the beneficial insects to hang around and not doing things that will harm them.
Sharp water streams can help with many insect pests, while many others may need an insecticidal soap spray, used very carefully. Understanding the life cycle of the various insect pests, as well as knowing which ones are most likely in your area, can help ifentify what you have and how to properly control them.

Search through the integrated pest management and organic gardening forums (fora?).

I found that a simple spray made with water, garlic, and oil soap deterred a lot of 'pests' from my gardens last year. Just pulverize a couple of cloves of garlic and place in lukewarm water overnight. Next day, strain the liquid into a spray bottle and add a smidgeon of, well, I use Miss Murphy's Oil Soap. A teaspoon is good - even less. It's a biodegradable product made from vegetable oils so will adhere to the plants slightly.

Give it a good shake before using.

I also have to second the suggestion of inviting birds. Their population here has increased due to feeders and birdhouses and baths, and they are a big help!