Beneficial insects can help protect landscape

By Bill Geer

Published: June 12, 2008

Q:How can I attract more beneficial insects to my garden?

A:Insect pests catch a great deal of attention in the plant world. But more important and certainly more numerous are the beneficial insects that quietly go about their business pollinating our crops, decomposing waste and preying on garden pests.

Many of our garden friends go unnoticed by even the most dedicated gardener. Some are simply too tiny to see, such as many of the specialized predatory wasps we call parasitoids. Others come out to feed at night, when we are asleep. Many beetles fall into this category. It is important that we get to know insects a little better and do what we can to encourage them to thrive in the garden.

Beneficial insects come in many shapes and sizes, from the minute pirate bug to the giant praying mantis. The following is just a short list of the most common beneficial insects present in the home landscape. Of course, there are many others.

Beetles: Ground beetle, lady beetle, rove beetle, tiger beetle, lightning bugs.

Flies: Hover or flower fly, robber fly, parasitic flies.

True Bugs: Pirate bug, assassin bug, ambush bug, damsel bug, big-eyed bug, stinkbug.

Lacewings: Brown and green lacewings.

Wasps: Predatory and parasitoid wasps.

Others: Mantises, spiders, dragonflies, damselflies, centipedes.

Even if you do not recognize all of the many natural enemies at work in the garden, there is much you can do to attract them to the garden. Like any organism, insects need food, shelter, and water. Water features attract a great many beneficial animals, including frogs, toads, lizards, and birds. Water also attracts insects such as the dragonfly, a voracious insect feeder.

Beneficial insects need shelter from the sun and wind and from other predators. Nocturnal insects need a place to hide during the day. Many materials we commonly use in the landscape provide excellent shelter for natural enemies. Rocks, logs and pieces of bark provide a great place to hide. Organic mulches such as wood chips and straw likewise can be used as shelter.

Insects also need a place to spend the winter. Perennials and ornamental grasses are ideal overwintering sites. Wait to cut these plants back until spring. In a vegetable garden, cover crops can provide winter shelter.

Predators, of course, feed on insects and other invertebrates, but they also use supplemental food sources, mainly pollen and nectar from flowers. Planting an abundance of flowers throughout the landscape is the best way to attract beneficial insects to the garden.

Plants used to attract beneficial insects include a number of garden favorites. And many of the plants are also attractive to butterflies.

Several common herbs, when allowed to flower, are also highly attractive to beneficial insects.

Some of these herbs spread quickly if allowed to seed; remove flower heads when blooms fade to avoid seeding.

The following is a list of good plants that attract good insects.

•Aster family (Compositae):

Blanket flower – Gaillardia spp.

Cone flower – Echinacea spp.

Coreopsis – Coreopsis spp.

Shasta daisy – Chrysanhemum maximum.

Calendula – Calendula spp.

Asters – Aster spp.

Zinnia – Zinnia spp.

Dahlia – Dahlia spp.

Cosmos – Cosmos spp.

Sunflower – Helianthus spp.

Yarrow – Achillea spp.

Goldenrod – Solidago spp.

Tansy – Tanacetum vulgare.

•Carrot family (Umbelliferae):

Caraway – Carum carvi.

Coriander – Coriandrum sativum.

Dill – Anethum graveolens.

Fennel – Foeniculum vulgare.

Queen Anne's Lace (wild carrot) – Daucus carota.

Wild parsnip – Pastinaca sativa.

Flowering ammi/Bishop's flower – ammi majus.

Toothpick ammi – Ammi visnaga.

•Pea family (Leguminaceae):

Alfalfa – Medicago sativa.

Clover – Melilotius spp.

Fava bean – Vicia fava.

•Mustard family (Brassicaceae):

Basket-of-gold alyssum – Aurinium saxatilis.

Sweet alyssum – Lobularia maritime.

Hoary alyssum – Berteroa incana.

Mustards – Brassica spp.

Yellow rocket – Barbarea vulgaris.

•Other plant families:

Beebalm – Monarda spp.

Speedwell – Veronica spp.

Cinquefoil – Potentilla spp.

Milkweed – Asclepias spp.

Buckwheat – Fagopyrum sagittatum.

Phacelia – Phacelia spp.

Bill Geer is director of the Oklahoma County Extension Service. His column addresses frequently asked horticulture questions. For more information, call 713-1125.

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