Why do large monoculture farms use so many pesticides? Because, their huge fields of a single crop are like big neon signs to insects that like to feed on them, saying, "24 Hour All You Can Eat Diner!" The model of long lines of straight rows of a single crop is like a food buffet to pests. A 'messy' garden with lots of different kinds of plants creates a more natural environment that lets nature work with you instead of against you. Even in the smaller environment of a residential garden, you will have more pest problems if you grow nothing but twenty varieties of tomatoes than if you grow twenty different species of plants. A synergistic garden includes a diversity of vegetables, herbs, and flowers, attracting beneficial insects that keep pests in check. A really simple way to do this is to separate similar crops (even by just a few feet), grow a few herbs or flowers in between your vegetable crops, and let some of your herbs produce flowers.
Attract Beneficial Insects
Along with a diversified garden, you can also lure more beneficial insects to your garden by planting specific plants that lure them with food sources and/or reproduction habitats. Planting a variety of these, especially so you have some of them blooming throughout the season is ideal. Some of these plants include:
Some of the beneficial insects include: bees (pollinators), lady bugs (larvae and adults eat aphids), green lacewings (eat spider mites), ground beetles (eat pest larvae, slugs, snails), soldier beetles (eat aphids, cucumber beetles, grasshopper eggs), spiders (eat a variety of insects), praying mantises (eat many pests including beetles and grasshoppers), and trichogramma wasps (their larvae feed on cabbage worms, corn earworms, tomato hornworms)
A trap crop is a planting made around or near another crop to draw pests away. It won't be eaten by you; it will be sacrificed as an offering to the pests and pulled up before it completes its lifecycle. This method is more experimental, as not all experts agree on its effectiveness, and some worry that trap crops will actually draw more pests to the garden. But, it is a method worth experimenting with in your garden. For example, radishes are a pretty big draw to flea beetles in spring, so planting them near other brassicas may keep them busy enough to ignore the other plants. Other examples are planting dill and lovage near tomatoes to draw hornworms away, and planting nasturtiums near lettuce to draw aphids away. Planting 10-20% trap crop near the main crop you are trying to protect is a common method.
Grow Healthy Plants With Better Defense Systems
Have you ever heard that predators in the wild look first for the weakest animal in the herd? It's also true in the plant world. A plant that is getting its needs met (nutritious bio-diverse soil, adequate water, plentiful sunlight, and good air circulation) is less attractive to predators and can divert more of its resources from survival to defense. Healthy vegetable plants produce more antioxidants, substances that are nutritious for us, but deterrents to predators. When you grow your plants in ideal conditions, you give them the resources they need to defend themselves.
Use Floating Row Covers
A floating row cover is a light, gauzy type of material (available at your local garden center) that protects plants from flying pests like aphids, flea beetles, and birds. It allows enough sunlight through for plants to grow, protects plants from frost in spring or fall, and provides a little shade for cool season crops, like lettuce, in summer. For plants requiring pollination to produce fruit (i.e. squash, pumpkins), you must take it off in the morning for a few hours to allow access for bees and other pollinating insects.
Try Natural Solutions
There are many natural pest control solution ideas out there. Other than being more environmentally friendly, the most important thing to know about them is that it may take persistence and multiple applications to get the desired results. For instance, a blast of water from a hose is often recommended to remove aphids from plants. Yes, it can work, but realize that you may have to do it more than once to get rid of them, or combine this method with a release of lady bugs to get the aphids under control. A non-toxic homemade insecticidal soap is another very popular natural pest control method. You can make a simple solution by mixing 5 tablespoons of liquid dish detergent in 1 gallon of water. Fill a spray bottle with this solution and spray the entire affected plant, especially the undersides of leaves. The solution kills them by suffocating them and is ineffective once it dries, so wash plants off within a few hours of application. You can spray your plants once a week with this solution, but avoid applying it during really hot weather to prevent foliage damage. Alternative additional ingredients include crushed garlic or hot pepper which act as a deterrent to future invaders. Insecticidal soap is effective against spider mites, aphids, mealybugs, other soft-bodied pests, eggs of pests, and young larvae of pests.
Time Your Plantings
If you have had repeated failures with a certain crop because of pests, it may be a good idea to switch your growing season where possible. For example, if flea beetles are skeletonizing your brassicas (broccoli, cabbage, cauliflower, kale, mustard, radish) every spring, you may be amazed by how much better they grow if you plant in later summer for a fall crop, instead. In fall, pests are winding down and will be less likely to cause problems. Cool season crops are also more likely to achieve a large size without bolting when the weather is cooler. Obviously, switching planting seasons isn't a luxury available in cold climates for warm season crops, but you could consider planting successive crops throughout the summer. If squash beetles decimate your first planting of pumpkins in spring, they may not attack the second crop planted a month later. Then, with a little frost protection in fall, you still may get a great crop!
There are lots of great choices when it comes to natural ways to treat garden problems. There is, however, nothing better than prevention. Keeping an eye on the health of plants and cycling of insects in your garden will give you an accurate assessment of what is necessary to maintaing a healthy, beautiful, and productive garden. Well-tended gardens are less apt to suffer devestating infestations. Walking through your garden at least three times a week, inspecting plants closely, will help you recognize, treat, and prevent problems before they get out of control.