Several species of arthropods favor vegetable gardens as a primary source of food. Unfortunately, large populations of those bugs can wreak havoc in gardens. Keeping pests off your crops doesn't have to mean using potentially dangerous chemicals and insecticides; several methods of natural pest control are effective and considered inexpensive.
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One of the most natural methods for controlling pest populations in a garden is ensuring that beneficial insects -- predators of pests -- call your garden home. Mantids, lacewings, ladybugs, hover flies and wasps all help keep pest populations down. Although not insects, spiders are also beneficial predators to have in your garden.
Using broad-spectrum pesticides kills beneficial insects as well as pest insects, creating a cycle of pesticide use. Lacewing, mantid and ladybug eggs are available at garden centers and from online retailers.
Insecticidal soap works by covering soft-bodied pests -- such as aphids, whiteflies, young boxelder bugs, Japanese beetles, spider mites and mealybugs -- and disrupting their cell membranes, causing the pests to lose body water too quickly.
Traditionally, insecticidal soap was made of dish-washing soap and water. Although making your own insecticidal soap using those ingredients is possible, soaps and detergents have changed greatly through the years and now aren't as effective against pests or as cost-effective as they used to be. Soap ingredients now include fragrance, lotion, anti-bacterial agents and surfactants, all of which may damage plants.
Many organically friendly insecticidal soaps line the shelves of garden centers and plant nurseries in convenient, ready-to-use formulas. You can make your own version, however, by diluting 4 teaspoons of an original-formula, liquid dish soap in 1 quart of water to make a 2-percent solution.
An insecticidal soap must be sprayed on entire plants to ensure the product covers the pests. Spray early in the morning or late in the afternoon to reduce the risk of the soap solution drying too quickly. Reapply it every four to seven days as needed. Many insecticidal soaps -- homemade or store-bought -- can damage some kinds of plants. So test small areas of leaves to ensure the soap you use is safe for your plants.
Bacillus thuringiensis, commonly called Bt, is a naturally occurring bacterium that is particularly effective in killing caterpillars, which are among the most prevalent garden pests. Different strains of Bt are effective against other types of pests a well, including mosquito and beetle larvae.
Bt works by disrupting and paralyzing a pest's digestive system, causing it to stop feeding. The pest dies from starvation, which can take several days. Bt does not harm non-target species such as bees or humans.
Pesticides containing Bt are available as either ready-to-use products or concentrates. One Bt concentrate directs users to mix 1 to 2 teaspoons of the concentrate with 1 gallon of water, but follow the directions on your product. Thoroughly spray all leaves with the solution every seven to 10 days as needed. About 2 to 3 ounces should cover 50 feet of a vegetable garden row.
Companion planting in a garden isn't always about pest control, but it can help repel certain pest species from favored plants. The basic principle is that certain plants grow better with other plants for a variety of reasons.
Basil (Ocimum basilicum) helps protect tomatoes (Solanum lycopersicum) from whiteflies and other pests. Basil also helps repel other kinds of flies, mosquitoes and aphids.
Chives (Allium schoenoprasum) can help protect carrots (Daucus carota var. sativus) from carrot rust fly.
Gardeners have a vast arsenal of natural and environmentally safe products and methods to use to help repel and control pest populations. In cases of severe infestations, commercially available, chemical pesticides may be warranted, but they are a last resort in the fight against vegetable-destroying insect pests.