NPIPM:Mycetophilidae
Authors: Ashley Mueller, Buyung Hadi
Flies are one of the most recognizable pests in the home. While they can be a nuisance, some species are a cause for health concern. These medically important flies are capable of transmitting bacteria and other disease-producing organisms that can affect the human digestive system.
Flies undergo four developmental stages: egg, larval, pupal, and adult. Flies are attracted to decaying organic materials. Places in the home where they are likely to reside are near room-temperature ripened produce and seldom-used drains and sinks. Adult flies are primarily active during the day, so they are often noticed. Preventing and managing flies indoors requires proper food storage and good sanitation practices in the kitchen and regular cleaning of areas that could be optimal breeding sites.
Identification
Fungus gnats (various species) are fragile-bodied gnats about 1/10 to 1/8 inch in length. Without closely looking, they can be confused for a mosquito. They are dark in color, and their wings have a “Y”-shaped wing-vein. The larvae are translucent and wormlike, with a black head capsule. They live in the growing medium of houseplants.
Habitat
Fungus gnats are often found near houseplants. They require damp organic matter, which includes potting soil, grass clippings, and compost to develop. Depending on the moisture level, the larvae can usually be found in the top two to three inches of the growing medium. In homes, adults are usually seen near an infested plant, although they may fly short distances. They tend to gather around window frames.
Life Cycle and Seasonal History
Fungus gnats have a very short life cycle, completed in three to four weeks at room temperature. They will reproduce continuously year-round indoors. In their adult life, females will lay about 150 eggs into the growing media. The eggs hatch within a week. The larvae mature in about two weeks, and then they construct pupal cases. The pupal stage lasts about four days, and they emerge as adults. Adult fungus gnats live for only seven to 10 days.
Fungus gnats are generally a noticeable indoor nuisance during the fall and winter months. During this time, decreased day length and cooler temperatures slow plant growth rate. If the watering schedule is unchanged, the growth medium will retain more moisture, making it an ideal location for fungus gnats.
Human Interaction and Urban Impact
Fungus gnats are a minor economically important insect. Larvae can be considered a minor pest of houseplants. Although they primarily feed on fungi and decomposing plant material, they also can feed on leaves touching the growing surface and plant roots, causing plant damage. Plants affected by fungus gnats will wilt and not appear healthy.
Adult fungus gnats do not bite; they are harmless. However, if present in large numbers, they can be a nuisance.
Prevention and Management Approaches
Fungus gnats require damp organic matter to grow. Reducing these areas will help eliminate fungus gnat breeding sites. In greenhouse environments, allowing the soil to dry between waterings will also prevent gnat outbreaks. Other management options include screening windows and doors and keeping plants outside. Using sticky traps may be useful in reducing fungus gnat populations.
In serious situations, Bt (Bacillus thuringiensis) dust can be applied to plants and other problem areas. Always use precaution and follow the label carefully before using any insecticide. Insecticides have a certain amount of toxicity to mammals; children and pets are especially at risk.
Other Online Resources
For information regarding labels of chemical control options, please visit NPIC MAPL
