Invite Beneficial Insects Into Garden

In 2012, Cornell Garden Based Learning revived the tradition of focusing on a yearly garden education theme through our CCE county network. The 2013, “Beneficial Insects,” theme focuses on the fact that most insects found in and around residential homes and landscapes are either benign or beneficial. Less than 1 percent of insects in the world are pest problems, and we can minimize most pest problems by designing our gardens and landscapes to support healthy beneficial insect populations.

When you garden ecologically, the goal is to keep insect pests below population levels where they will cause unacceptable damage, rather than try to get rid of all of them. Inviting beneficial insects into your garden may be the most important and readily available biological control practice you can undertake in your battle against insect pests. As you rely on natural enemies to help you, you need to foster them by providing their needs. One method consists of increasing the diversity of plants in or near the garden to attract more beneficial insects to the area.

Beneficial insects play an important role in reducing and controlling populations of both plant and insect pests by acting as predators or parasitoids to these detrimental organisms. There are also insects that are innately beneficial because they act as pollinators or produce products (such as bees that pollinate and produce honey) that are useful to humans.

Predators such as lady beetles and lacewings are mainly free-living species that consume many prey during their lifetime. Parasitoids, which include many wasps and flies, are more specialized than predators; the immature stage actually develops within the body of a single insect, ultimately killing it. The adults are free living and often visit flowers for nectar and pollen.

Select plants for your garden that are known to lure beneficial insects to help you attract and conserve these garden helpers. Two large groups, or families of plants, are excellent “lures” the parsley family (Umbelliferae) and the sunflower or daisy family (Compositae).

You can spot members of the Umbelliferae family by their umbrella-shaped clusters of small 5-petaled flowers. The overall appearance is often a large flat head of white or yellow flowers; Queen Anne’s lace is a good example. The flower head provides a place to land for many insects, especially beneficial wasps. Using a variety of these plants that bloom at different times can make your garden look attractive, too. A number of culinary herbs in this plant family including parsley, dill, caraway, cilantro or coriander, and fennel. Some of these herbs are very attractive to syrphid and tachinid flies, assassin bugs, lacewings and parasitic wasps. One caution – these plants will spread quickly if left to go to seed, so remove flower heads after they stop producing nectar, but before seeds mature. Also, some are biennials, so you won’t see flowers appear for a year.

The Compositae family is characterized by flower heads that are actually made up of many small flowers growing together. Many flowers are composed of rays around a disk-like center. Many well-known ornamental flowers including marigolds, dahlias, daisies, asters, cosmos, calendula, coreopsis, tansy, yarrow, zinnia and sunflowers are in this family. Flowering often lasts over a long period of time, and there is usually more than one flower per plant. This provides a slow flow of nectar over a long period for the insects. Ladybugs, lacewings, parasitic wasps and some predaceous wasps are attracted to plants in this family. Soldier beetles, flower beetles and some lady beetles will feed on pollen in addition to feeding on insects. Dandelions offer early spring pollen to some of these insect predators.

Legumes such as clovers and vetch also attract beneficials. They add nitrogen to the soil, provide good shelter and moisture for insects, and may even serve as a source of alternative prey for natural enemies. Beneficial insects such as ground beetles, rove beetles and robber fly larvae are often found in the soil.

Cover crops offer protection to beneficial insects when our annual garden plants are not actively growing. Often, beneficial insects move over from the cover crops as these crops begin to die back, feeding on “bad” insects that are in turn consuming the desirable garden plants. Buckwheat is a good one because it not only provides shelter, but has flowers which attract flies, ladybugs and pollinating bees. One caution, however, is that it does self-seed readily. A small permanent planting of buckwheat near the garden allows immature natural enemies to complete development without seeding up your garden.

If attracting – and keeping – the “good guys” to your garden is what you would like to do, try planting a few of the “lure” plants from the parsley and sunflower families this year.

For more information on beneficial insects, visit: blogs.cornell.edu/horticulture/insects/.

The mission of the Chautauqua County Master Gardener Program is to educate and serve the community, utilizing university and research-based horticultural information. Volunteers are from the community who have successfully completed 50-plus hours of Cornell approved training and volunteer a minimum of 50 hours per year.

For more information on the Master Gardener Program, contact: Betsy Burgeson, Master Gardener coordinator at 664-9502, ext. 204, or email Emh92@cornell.edu.