The Vegetable Garden

Controlling Insects Organically

  • Written by Kathy Anderson

Most gardeners are anxious to get out into their gardens as soon as the weather warms up and the first green sprout appears. Unfortunately, plant-eating insects are just as anxious as we are to get into the garden. They seem to think that our beautiful shrubs and tasty vegetables were planted for their benefit!

There are many fine products available in catalogs and garden centers to control insects. But for health or environmental reasons, some gardeners are hesitant to use chemicals in their garden, especially in a vegetable garden.

So what can you do to avoid sharing your beautiful flowers, shrubs and vegetables with every insect that passes through the neighborhood without using potentially harmful chemicals?

Practicing good garden housekeeping should be your first defense in the battle of gardener versus insects. In other words, keep a clean garden and don’t give the insects a place to hide and reproduce. Rake up any dead leaves from the ground and discard them, or better yet, add them to your compost. Harvest vegetables as soon as they ripen, and don’t leave over-ripe vegetables in the garden. Clear out all dead foliage from your gardens in the fall. Prune out any dead or damaged branches from your trees and shrubs, making clean cuts without ragged edges where insects can hide.

If you find insect damage on your plants, there are a large number of organic products that work in a variety of ways to kill insects or discourage them from eating your garden plants. Because many organic insect controls are used for specific types of insects, it is very important to know what insects you are dealing with before choosing the correct organic insecticide. Carefully examine the damaged plant to find the culprits, looking under the leaves and along the stems where they may be hiding. Your county’s Ag Extension Agent can help identify specific insects, or you can also do an online search for insect identification sites.

Butterflies often lay their eggs on plants, and when those eggs hatch the little caterpillars will stay and feed on the plant as they grow. Caterpillars can be controlled using a common organic insecticide known as Bacillus thuringiensis, or Bt. Bt is a naturally occurring bacteria that causes caterpillars to stop eating and die. There are several varieties of Bt that can be used, depending on the type of caterpillar you’re after, including one specific to Colorado potato beetle larvae and another for corn earworms. Bt is also effective against tomato hornworms, the little green worms that like broccoli and cabbage, and bagworms. Bt should be applied at 1-2 week intervals to kill succeeding generations of insects. Gardeners with butterfly gardens should avoid using Bt on their plants because it is harmful to butterfly caterpillars. However, Bt is completely harmless to pets and people.

Diatomaceous earth is another natural insecticide that may be used on a variety of insects. Diatomaceous earth is a fine powder that feels like talc, but it is actually the fossilized skeletal remains of small aquatic critters called diatoms. It is completely harmless to people and pets, but when soft-bodied insects come in contact with it, the tiny sharp edges of the diatoms lacerate the insects, making them dehydrate and perish. Apply diatomaceous earth in the early morning or evening when the plants are wet with dew, which will make the powder stick to the surface of the leaves and doom the insects that walk through it. Diatomaceous earth can be used to control ants, aphids, beetle grubs, box-elder bugs, flea beetles, those nasty little earwigs and many more insects. It’s also safe to use on houseplants, and can even be sprinkled on the ground to control slugs.

Insecticidal soap is another favorite organic insect control. Safe to use around bees, birds, and animals, insecticidal soap is made of fatty acid salts. It can be used in the garden and on houseplants to control aphids, spider mites, whiteflies and some leafhoppers and caterpillars. The drawback to insecticidal soap is that it must be sprayed directly onto the offending insects to be effective. Insects breathe through their shells, and insecticidal soap suffocates insects by coating their shells so they cannot breathe. Insecticidal soap must be applied thoroughly and repeatedly for the best results.

There are also plant-based insecticides available. The seeds of the Neem tree produce an oil that disrupts insects’ reproductive cycle, preventing them from multiplying. The Neem tree is native to Southeast Asia and is also grown now in Australia for its insecticidal properties. Neem works quickly and is effective against a variety of caterpillars, beetles, aphids and borers.

Many insects are actually fussy eaters and they won’t eat plants that are distasteful to them. If you’ve grown garlic you may have noticed that insects leave it alone. You can find insect repellants made with garlic that can be sprayed onto plants to prevent insects from eating them. These garlic-based insect repellents become odorless within five minutes after they’re applied and leave no aftertaste on food crops. The plants actually absorb the garlic and stay distasteful to insects for up to a month. There are also garden insect repellants available that are made with hot peppers. Like the garlic-based repellants, the hot pepper repellants are sprayed on the plants to make them distasteful to insects.

Organic insecticides and insect repellants are becoming available at more garden centers and gardening catalogs every year. It is not difficult to control insects with organic insecticides, but the organic gardener must be diligent with frequent plant inspections and take prompt action to avoid infestations when insect damage is found in the garden.

Kathy Anderson has been an avid gardener for many years and has grown tomatoes by the acre, along with many other vegetables, flowers and landscape plants. Kathy recommends as a great place to learn more about gardening. Article provided by .