In a food garden, nonchemical control of insects is an important advantage of Integrated Pest Management (IPM). Vegetable gardeners can discourage destructive insects and keep the beneficial ones through cultural practices, mechanical methods, and biological controls.
Adopt good cultural practices.
Healthy plants are more resistant to insect infestation than unhealthy ones. There are several practices gardeners can adopt to have healthier plants. Choose disease-free and insect-free seeds and seedlings. Be conscientious about soil preparation and maintenance. Rotate the position of your crops from year to year. Plant your seeds at the appropriate time for maximum growth, and thin seedlings and remove weeds to reduce competition. Discourage insects by interplanting different vegetables rather than attracting them to a large planting of a single crop. Add “trap” crops—plants attractive to specific insects—to lure destructive pests away where they can be removed or treated. For example, zinnias can attract Japanese beetles that might attack your corn or beans.
Employ mechanical methods.
Use traps, barriers, and handpicking to remove insects from your vegetable garden. Traps to try include yellow dish pans of soapy water to attract and drown aphids, yellow boards coated with oil or grease to attract and trap whiteflies and cucumber beetles, and shallow tins of beer set at soil level to trap slugs. Barriers can range from collars of cardboard or tin to discourage cutworms, to nets or screens covering seedlings to prevent insect and animal damage.
Physically removing insects or their eggs by hand is one of the most effective mechanical control methods. Drop pests into a jar with a small amount of water; finish the job by pouring in boiling water. Spraying aphid- or spider mite-infested plants with a strong stream of water can go a long way toward reducing the insect population.
Introduce biological controls.
Biological controls include using parasites, pathogens, and predators. Introduce natural parasites such as nematodes to your garden to kill vine borers, grubs, weevils, and armyworms. Or use pathogens such as bacteria (Bt—Bacillus thuringiensis) to kill caterpillars. These biological controls require an understanding of the life cycles of the parasites, pathogens, and insects. Insect predators to encourage in your vegetable garden can range from ladybeetles and spiders to birds and frogs. Including plants in your vegetable garden to provide a haven for predators will also attract pollinators, such as bees and butterflies.
IPM mixes techniques to achieve results.
Using all these methods in an Integrated Pest Management plan is just that: integrated. Removing all insects is neither desirable nor possible, but mixing cultural, mechanical, and biological methods helps control unwanted insects in the garden. Using this approach to vegetable gardening is a matter of common sense and conscientious effort. It’s IPM.
(Visit http://www4.ncsu.edu/~dorr to learn more at the Biological Control Information Center.)
Written by Mary Alice Ramsey, Extension Master Gardener Volunteer.