Most gardeners know that not every insect is a bad insect. There are an estimated 900,000 species of insects in the world according to the Smithsonian, making up eighty percent of all living beings. The United States alone has almost 100,000 species of insects. Only a few of those insects are harmful to us and our gardens. In fact, most of the insects we encounter are harmless or are beneficial. The beneficial insects pollinate flowers, eat bad insects, and bring beauty to the world.
Beneficial insects can be divided into roughly four categories:
- Predators such as lady beetles
- Parasitoids and parasites (Wasps that lay eggs on caterpillars and feed on their bodies)
- Decomposers such as dung beetles and other insects found around the compost pile
- Pollinators such as bees, wasps, flies, and butterflies
In addition to their contributions to our garden, insects often provide a protein rich meal for birds and other creatures. This attracts interesting birds and animals to your garden.
Some of the best beneficial insects to release in your garden are:
- Green Lacewings–These are generalist predators that feed on aphids, immature whiteflies, thrips, spider mites, mealybugs, small caterpillars and other soft bodied pests. They are attracted to dill and coriander.
- Lady beetles–These eat aphids, white flies, and Colorado potato beetles. They are attracted to dill and dandelions.
- Praying Mantis–These are apex predators and eat pretty much everything, including spiders, caterpillars and anything else that crosses their path.
- Beneficial nematodes–controls grubs, fungus gnats, fleas, and up to two hundred other insects that have a life cycle that includes living in the soil.
- Trichogramma–wasps that lay their eggs on moth eggs and then their larvae eat the eggs when the wasps hatch.
- Ground beetle–This is a nocturnal beetle that eats slugs, snails, cut worms, cabbage maggots, and nearly anything else that lives on the ground of your garden. Plant perennial flowers around your garden to provide a habitat for this beetle and keep it around your garden.
- Soldier beetles–These beetles feed on aphids and caterpillars. They will eat just about any insect they come across, including beneficial insects. Plant catnip, goldenrod, and hydrangea to attract this beetle.
In integrated pest management, beneficial insects are the first line of defense when harmful insects are detected. Instead of immediately using a pesticide, you release the appropriate beneficial insect to control the problem. They then eat or otherwise deal with the problem insect. However, you must be able to tolerate a small population of problem insects to feed the beneficial insects and persuade them to stay around.
Many people plant things that beneficial insects like around their garden to keep them near enough to keep problem insects to an acceptable level. Fennel, calendula, coriander, dill, and cosmos are all considered good plants for attracting beneficials.