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Types of garden flies and how they help control pest populations

In the Garden

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Flies are good??? What about mosquitoes, fungus gnats, no-see-ums, tsetse flies and others?

Many members of the family of flies (Diptera order) are beneficial. At the very least, most flies are critical decomposers. However, there are some that actually help control common garden pests.

Here are the most notable predatory or parasitoid flies:

Aphid predatory midge

The aphid predatory midge resembles a mosquito without the stylet proboscis. The adults feed on nectar and honeydew. The larvae feed on aphids that are often larger than they are. Aphid predatory midges are often overlooked as they are so small, but they are highly beneficial. They will have three to six generations per year.

aphid fly
Aphid predatory midge larva among aphids and thrips. | Photo Ron Patterson, UI Extension Coordinator

Syrphid (or Hover) fly

syphid fly
Adult syrphid fly. | Photo Whitney Cranshaw, Colorado State University, Bugwood.org

long legged fly
Syrphid fly larva feeding on aphids. | Photo Clemson University-USDA Cooperative Extension Slide Series, Bugwood.org

There are about 900 known syrphid fly species in North America. Their hovering flight pattern resembles that of bees, and many species have coloration similar to bees. Adults require pollen and nectar to reproduce. Larvae feed on aphids, leafhoppers, pear psylla, scale insects, spider mites, thrips, and other soft-bodied insects. They will have three or more generations per year. One larva can consume up to 400 soft-bodied insects in its lifetime.

Long-legged fly

long legged fly1
Long-legged fly adult. | Photo Clemson University-USDA Cooperative Extension Slide Series, Bugwood.org

tachinid fly
Long-legged fly larva. | Photo Gerald J. Lenhard, Louisiana State University, Bugwood.org

Both adult and larvae long-legged flies prey on springtails, aphids, gnats, midges, other flies, thrips, and insect eggs. Adults often have a metallic color (green, blue or copper).

Tachinid fly

t fly pic
Adult tachinid fly. Photo Joseph Berger, Bugwood.org.

t fly 2
Tachinid fly eggs on caterpillar head. Photo Ken Chamberlain, The Ohio State University, Bugwood.org

There are about 1300 known tachinid fly species in North America. Adults feed on honeydew and nectar. Some species lay their eggs on the host, others on the host’s food (the larvae then need to search out the host), still others lay live larvae in, on or near the host. Tachinid flies have a wider host range than parasitic wasps.

Robber fly

robber fly
Adult robber fly feeding on a honeybee. | Photo Jessica Louque, Smithers Viscient, Bugwood.org

robber fly 2
Adult robber fly feeding on a wasp. | Photo David Adams, Balanced Rock Photography, Bugwood.org

Robber fly larvae will feed on insects in the ground. The large “bearded” adults feed on larger insects such as bees, dragonflies, grasshoppers, wasps, other flies, and more. As generalist predators they feed on both pests and beneficial insects but are generally considered to be beneficial.

Conserve and encourage beneficial Diptera

  • Learn to differentiate between pest and beneficial insects.
  • Avoid using broad-spectrum insecticides.
  • Limit tillage and burning to provide over-wintering habitat.
  • Plan for summer-long blooms to provide pollen and nectar.
  • Allow for some pests to attract the beneficial insects.
  • Provide a moist, shady environment.
  • Plant cover crops.

When you scout your flower beds and gardens, look for the good guys, especially the larvae of these flies, that will help with some of your pest issues.

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