Gnats

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Fungus gnats are pests of greenhouses, nurseries, and around interior house plants. Fungus gnats are considered a nuisance by their presence in and around structures, especially when they appear in large numbers.

HOW DO I KNOW IF I HAVE FUNGUS GNATS?

  • Adult fungus flies may be noticed flying around house plants, or around light fixtures, or gathered at a nearby window.
  • Fungus gnats typically fly in short, erratic paths.
  • Moving your houseplants around will often cause the fungus gnats to fly out.
  • You may also notice fungus gnats more during the fall and winter, especially if you move outdoor potted plants inside.

WHAT DO FUNGUS GNATS LOOK LIKE?

  • Adult fungus gnats are small, mosquito-like flies that are 1/8” in length.
  • The fungus gnats’ fragile, grayish to black body has long, slender legs and thread-like antennae.
  • Fungus gnats have one pair of clear or smokey-colored wings, with no pattern and few distinct veins (the common Bradysia species have a Y-shaped wing vein).
  • Fungus gnat larvae are clear to creamy-white and can grow to about ¼” inch in length.
  • Larvae have shiny black head capsules.

ARE FUNGUS GNATS DANGEROUS?

  • Fungus gnats do not bite, sting, or spread human pathogens or diseases.
  • However, fungus gnat larvae can damage houseplants and seedlings.

CAN MY PLANTS BE DAMAGED BY FUNGUS GNATS?

  • Fungus gnats can be vectors for plant diseases including ones called Fusarium and Pythium, and even foliage pathogens like Botrytis.

  • Fungus gnat larvae may also feed on the roots of a plant, resulting in the plant becoming more susceptible to disease.

  • Symptoms that a plant has been damaged by fungus gnats include a sudden wilting or yellowing of the leaves, loss of vigor, and poor growth.

  • There will not be any visible injury to the plant above ground, but the roots will have small brown scars or the small feeding roots and root hairs will have been eaten off.

  • Plants prone to injury by fungus gnats include: geraniums, African violets, carnations, and poinsettias.

WHY ARE FUNGUS GNATS IN MY HOUSE OR YARD?

  • Fungus gnats come into your home attracted to light.

  • Fungus gnats are also attracted to moisture like under wet sinks, near leaky roofs or leaking water pipes, and in indoor plants that have been over-watered or have poor drainage systems.

  • Additionally, fungus gnats can survive in damp new construction materials and outdoors in moist, shaded areas that have decaying organic matter such as leaf litter, compost piles, grass clippings, feces, etc.

WHAT DO FUNGUS GNATS EAT?

  • Fungus gnat larvae feed on fungi and decomposing organic material in soil are the main food sources for adult fungus gnats.

  • Fungus gnat larvae feed on the tiny root hairs of plants and on highly organic soil.

WHAT IS THE LIFECYCLE OF A FUNGUS GNAT?

  • Adult female fungus gnats are particularly attracted to breeding areas that have rich, organic materials and high moisture content -- precisely the conditions of indoor potted plants.

  • Females lay up to 100 to 300 eggs in 2 to 30 batches in decaying organic matter on the moist soil surface or in soil cracks.

  • Eggs hatch in 4 to 6 days

  • Fungus gnat larvae feed for 12 to 14 days on fungi and decaying organic matter, root hairs, and small feeder roots.

  • The pupal stage is completed in about 5 to 6 days.

  • Newly emerged adult fungus gnats live about 7 to 10 days.

  • At room temperatures between 65°F to 75°F, the fungus gnats complete their life cycle in 3-4 weeks, with continuous reproduction where warm temperatures are available.

  • There are many overlapping generations per year.

6 INTERESTING FACTS ABOUT GNATS:

  1. Some mushrooms mimic flowers to attract fungus gnats and pollinators, which help in spreading the spores to another mushroom (Dentinger et al., 2010).).

  2. All of the many species of fungus gnats are categorized into just two families: the Mycetophilidae or Sciaridae.

  3. Fungus gnats are closely related to mosquito.

  4. South American Pleurothallid orchids have very tiny flowers, which are pollinated by a very tiny species of gnats.

  5. Because of their appearance, black flies are called buffalo gnats. These flies are real biters; while fungus gnats cannot bite as their mouthparts are not suited for piecing and sucking blood.

  6. The swarm of gnats you accidentally walked through was a large group of male gnats called a “ghost”, swarming around a female, hoping to be her mate.