The Homeowners Column

The Homeowners Column

How to Attract Beneficial Insects to the Garden

Photo of Sandra Mason

Sandra Mason
Extension Educator, Horticulture
slmason@illinois.edu

It's a common case of mistaken identity. Just because you happen to look like some sort of bee you must endure a swat or a frantic scream. Hover flies are a common insect. Just as their name implies, hover flies often hover around flowers or around people. They are 3/8 to 3/4 of an inch long with black and yellow stripes. Some people call hover flies sweat bees since the flies enjoy a little tasty drink of sweat periodically. However, hover flies don't sting and actually can't sting even if they had the urge. Hover flies are actually good guys in the garden. Hover fly young are ravenous predators of garden pests such as aphids, thrips and small caterpillars. The adult hover flies do not eat other insects, but feed on nectar and pollen.

There are many other unsung and often misidentified heroes of the garden world. Some of the best beneficial insects are the parasitic wasps. The adult wasps seek out the eggs or larvae of specific insects (many times crop eating caterpillar pests). The wasps then lay their eggs in the pest. The wasp larvae develop inside the pest. Eventually the pest dies and the adult wasps emerge.

The good news is hover flies and many other good guys can be attracted into the garden with some simple techniques.

  • First, learn how to recognize common beneficial and pest insects.

  • Minimize or eliminate insecticide applications. Many insecticides will kill beneficial as well as pest insects. Even natural botanical insecticides such as rotenone will kill beneficial insects.

  • If insecticides are chosen as a control method, use selective insecticides. Selective insecticides are toxic to specific pests and will not directly harm beneficial insects. The microbial insecticide Bt sold as Dipel and Caterpillar Attack are toxic only to caterpillars that feed on the sprayed plants. Insecticidal soaps can also be effective on pest insects without harming beneficial ones.

  • Build it and they will come. Include a diversity of plants in the landscape. Include annual and perennial flowers, native grasses and plants, ground covers, shrubs and trees.

  • Plant a variety of flowers. Many predators and parasites feed on pollen and nectar or use flowers to supplement their food supply if they run low on pests. Plants in the carrot family and mustard family are especially attractive to beneficials. Use plenty of plants with small flowers such as sweet alyssum, dill, fennel, garlic chives, lovage, coriander (cilantro) and white lace flower (cultivated version of Queen Anne's Lace). Other popular plants for beneficials include: blanket flower, coneflower, coreopsis, cosmos, tansy, yarrow, goldenrod, sunflowers, yellow alyssum, sweet clover, buckwheat or hairy vetch. Let a few of the broccoli plants flower.

  • Plan a season of bloom. Gardeners enjoy having flowers all season as much as the beneficial insects.

  • Provide water areas with shallow dishes or pebble areas. The larger good guys, toads, will appreciate these areas too.

  • Include some permanent hardscapes such as stone paths and decorative rock.

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