Our list of beneficial insects includes spiders, even though technically they're not insects.
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Prevention and a self-sustaining, balanced ecosystem are the organic gardener's most important tools for minimizing diseases and pests. As with people, preventive medicine in plants means adopting a holistic approach from the beginning. Some diseases and insects can be minimized through proper garden sizing, crop rotation, companion planting, and soil maintenance.
As garden steward, your role is to determine the severity of the damage, keeping in mind that damage does not necessarily mean lower yields. Most plants can lose up to 20% of their foliage and still match the yields of those with little or no foliage loss. When trouble arises, learning to accept imperfections, some diseases, and some insects can be just as important as orchestrating a heavy-handed invasion of friendly insects. The following list outlines the advantages of 13 beneficial insects and will arm you appropriately when the time comes to do battle.
Insect and Benefit
Assassin bugs: Eat immature insects.
Bumblebees: Poll inate blossoms from which fruits and vegetables develop. One of nature's best helpers for our food supply.
Ground beetles: Eat caterpillars, cutworms, some species of slugs and snails, and soft-bodied larvae.
Lacewing wasps: Eat aphids, corn earworms, mealybugs, mites, leafhopper nymphs, thrips, caterpillar eggs, scales, and whiteflies.
Ladybugs: Eat aphids, mealybugs, and small insects. Different species of ladybugs prefer different insects.
Praying mantis: Eat aphids and small insects.
Syrphid flies: Eat aphids, leafhoppers, mealybugs, mites, scales, and small insects.
Spiders: Eat insects and other pests.
- Braconis: Parasitize aphids, larvae of moths, butterflies, many beetles.
- Chalcid: Parasitize aphids, mealybugs, scales, and larvae of beetles, moths, butterflies.
- Ichneumonid: Parasitize moth and butterfly larvae.
- Pediobius foveolatus: Parasitize Mexican bean beetle larvae.
- Trichogramma: Parasitize and eat eggs of the corn borer, cabbage looper, codling moth, and many caterpillars.
Adapted from The Organic Gardener's Home Reference (Storey Communications, 1994) by Tanya Denckla. Copyright© 1994 by Tanya Denckla.