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 As long as humans have lived in houses and cultivated plants, they have had to deal with a variety of insect and fungal pests. Synthetic pesticides are very effective at killing these invaders, but they also harm beneficial organisms and persist in the environment contaminating food crops and water sources. Instead of spraying toxic chemicals at the first sign of a problem, employ a natural, systematic approach to pest control using organic pesticides only as a last resort. The first step is to use proper planting practices and maintenance to reduce the numbers of invasive pests.
A healthy, vigorous plant will be less susceptible to pests than one that is stressed and weak. Below are several techniques that can maximize chances for strong plants.
Plant Selection
- Know your planting zone number and select only appropriate plants. These will be more likely to thrive in your area and will require less water and fertilizer.
- Consider native plants that have proven successful locally.
- Choose varieties that are disease- and pest-resistant. Plant-breeding techniques have produced versions of plants better suited against a variety of pests and weather conditions.
- When buying plants, select only healthy ones with good roots.
- Do a little research on the plant you want, and make sure you can meet its sunlight, moisture, pH and soil-type requirements.
Prepare the Soil
Before planting, test the soil to determine the nutrient levels and pH. Your local cooperative extension office may do the testing, or can lead you to companies that will. Once knowing the conditions in your soil, you can then add only what is needed. Amending the soil with compost will provide nutrients, aerate the soil and introduce a variety of beneficial organisms that may help in controlling pests.
Planting
- Adhere to the planting schedule recommended for your climate and crop. Planting too early or too late can result in unhealthy plants.
- Follow the spacing recommendations for the plant since many won’t grow as well when overcrowded.
- Rotate crops in gardens and flower beds from year to year to prevent a particular pest from building up to unmanageable levels.
- Periodically plant legumes such as peas, beans and clover to naturally enrich the soil with nitrogen, reducing the need for fertilizer.
Strength in Diversity
Avoid monoculture by planting a diverse array of plants. Large plots with a single type of plant are easier for the pests to find. Diversity also provides insurance. Most pests only attack a specific plant, so an infestation would result in the loss of a few specimens, not the entire garden.
Proper Maintenance
Maintain the plants properly by follow the pruning guidelines. Pruning at the wrong time may weaken the plant or provide an entry point for a pest. Quickly remove infested sections to protect the rest of the plant and dispose of the affected parts away from the planting beds. Clear away the dead material from annual plants at the end of the year to eliminate pests that did invade.
Companion Planting
Companion planting exists in almost every agricultural culture, and while the exact mechanisms are not always well understood, many swear by the results. The principle involves the beneficial action, either physical or chemical, that different plants may provide each other. For example, when squash is planted with corn, the squash vines can provide ground cover preventing weed growth, and they can use the corn plants as a trellis for vertical growth. The multiple levels of growth are thought to confuse the adult squash vine borer, and the prickly squash vines discourage animals from damaging the corn.
Some plants naturally release chemicals that control weeds and pests. For example, marigolds release a chemical called thiopene that repels damaging nematode worms. Plants such as cucumbers, oats, alfalfa and sunflowers release chemicals that control weeds. The fragrance of some herbs repels or confuses pests that find plants using smell.
Certain companion plants attract beneficial organisms, such as lady bugs, spiders, wasps and praying mantises that prey on pests in the garden. Appendix A of the National Sustainable Agriculture Information Service’s Pest Management Systems Guide contains a list of specific plants and the organisms they attract.
The first step to controlling pests without using harmful chemicals involves selecting the appropriate plants, and then planting and maintaining them correctly. With a little extra thought and care, you can grow strong, healthy plants and reduce the likelihood of infestation. Yet even with the best planning and care, pests will invade. Natural Pest Control, Parts 2 and 3, will cover ways to control pests without the use of synthetic chemicals.
See Part 2: Mineral, Plant and Microbial-Based Organic Pesticides
See Part 3: Replacing Pesticides with Insects, Worms, Birds, Bats and Other Beneficial Organisms
Additional resources:
Plant Selection Guidelines
List of Companion Plants
Companion Plants for Pest Control
Companion Planting Guide (pdf)
How to Plant a Vegetable Garden
What You Need to Know to Become an Urban Farmer
Breaking Down the Bones: How to Compost Meat and Other Animal Products
Composting 101: How to Make Compost
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