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.