There are many different types of insects that are observed in the garden each spring and summer. While some cause damage and often need to be controlled, many others are beneficial to have around. Beneficial insects can be grouped into at least three categories based on the services they provide including pollinators, natural enemies, and those that offer aesthetic value.
Approximately 40% of the flowering plants in North America are pollinated by insects. There is a vast number and variety of pollinators, many of which are native, including beetles, flies, wasps, and of course, bees. Vegetables in the home garden that require insect pollination include squash, zucchini, cucumbers, melons, and blueberries. Avoid using broad spectrum insecticides such as pyrethroids (bifenthrin, permethrin, cyfluthrin, etc.), carbamates (carbaryl), and organophosphates (malathion) when these plants are in bloom. Attract pollinators to the garden by including native flowering plants. For a list of native plants, see HGIC 1727, Pollinator Gardening and for more information on native pollinators, see HGIC 1733, Native Pollinators.
The vast majority of insect pests have natural enemies. Beneficial insects help control pest insects by feeding on them or laying eggs within them. Natural enemies can be described as predatory, feeding on many different insects, or parasitic insects, which take resources from only one individual insect. Common predatory insects (and their prey) include lady beetles (aphids), assassin bugs (caterpillars and many others), ground and tiger beetles (caterpillars, maggots, aphids, etc.), and mantids (moths, stink bugs, grasshoppers, etc.). Common parasitic insects include tachinid flies (caterpillars, leaf footed bugs, etc.) and numerous wasp species (caterpillars, aphids, scale, beetle, etc.). Natural enemies can be a great help in keeping pest insect populations below damaging levels. Gardeners should always positively identify insects found in the garden to ensure natural enemies are spared. Local County Extension Agents are available to assist with identification when needed.
Some insects are beneficial simply because they are aesthetically pleasing. The most easily observed examples are butterflies and certain species of moths. Both flutter from flower to flower foraging for nectar and contributing to pollination along the way. Butterflies and moths are valued for their variety of colors and shapes, and the juvenile caterpillars are often equally unique. Many gardeners plant flowers and shrubs, such as butterfly bush, lantana, coneflower, and black-eyed Susans to attract them to the garden. Don’t forget to plant species for caterpillars to feed on, such as dill, fennel, butterfly weed, and milkweed. For more information, see HGIC 1701, Butterflies in the Garden and HGIC 1734, Urban Wildlife – Butterflies.