Sustainable Gardening

Beneficial Insects and Their Importance in the Garden

Syrphid fly on a zinnia

Common insect pests have natural enemies; these beneficial insects reside in and around the landscape and may provide a biological option to minimize garden pest infestations.

Before the growing season takes off this year, here are some tips that may encourage natural enemies to visit, establish, and thrive in your garden areas.

Use an integrated approach

There are many available tactics for reducing pest problems in the garden depending on one’s particular needs and management style for healthy plant production. The NCSU Biological Control Information Center provides a great overview of integrated pest management (IPM) and its benefits for the avid gardener. A few of the following options may be useful prior to the peak-growing season.

Be prepared

Know your garden pest and the beneficial insects that can help you control them. Natural enemies are biological control agents that attack key insect pests. Some prey on a wide variety of insect pests while others prey on a small, specific number of pest species. It is critical to be able to properly identify the correct insect pest that causes damage in the garden. Get to know your local county extension center and the NCSU Plant Disease and Insect Clinic for quick resources in pest identification.

Take action

Be familiar with the history of insect pest outbreaks in the garden landscape. If, for example, aphids consistently colonize on many plants within your garden every year, efforts should be taken to support the preferred habitats of aphid predators like lady beetles, syrphid flies, and minute pirate bugs. For major foliage feeders, like cabbage loopers, products containing Bacillus thuringensis (Bt) are selective biological agents for caterpillar pest control. This pest history provides a timeline for expected pest outbreaks for the upcoming season and gives estimated times to start scouting susceptible plants for the presence of particular insect pests.

Modify your landscape

A number of factors can influence the conservation of beneficial insects in the garden. As warmer temperatures arrive, beneficial insects emerge from their overwintering refuges and desperately search for food nourishment. Pollen and nectar are high-energy alternative food sources for natural enemies. Planting early- and late-flowering plants can enhance the alternative food sources for beneficial insects, including pollinating insects like bees, and encourage their visitation to your garden. Alternatively, another option to consider is to maintain nearby habitats that provide permanent refuges for beneficial insects. Predacious ground beetles, for instance, are very effective ground-dwelling predators of major insect pests that can only travel limited distances from their native habitats to forage for food. Scientific research has shown that setting up “beetle banks,” or natural, undisturbed plant strips, have been effective for maintaining high populations of natural enemy populations like ground beetles. These options are only a few of many listed for IPM approaches.

Use pesticides that target the pest not the beneficial insects

Every year, newer pesticide chemistries are being developed to more effectively target key pests with minimal impact on the environment. Chemical control may be an option if a particular pest infestation has been impossible to control through other methods. This is where proper pest identification is critical for selecting the most appropriate insecticide that will selectively kill the target pest while minimally affecting beneficial insect populations.

Emily Mueller, PhD Entomology, is at the Wake County Cooperative Extension office.

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