Fungus Gnats

What are Fungus Gnats?

Fungus gnats are small, flying insects commonly found in houseplants, greenhouses, and other indoor growing environments. They are attracted to moist soil and organic matter, and their larvae feed on fungi and decaying plant material.

Orfelia and Bradysia are both genera of fungus gnats in the family Sciaridae. Bradysia is a very large and diverse genus that includes many species commonly found in indoor growing environments, while Orfelia is a smaller genus that includes several species found in both indoor and outdoor environments.

While they do not cause significant damage to plants, fungus gnats can be a nuisance, and their larvae can stunt the growth of young plants.

Host Plants

Fungus gnats are attracted to a variety of indoor plants, particularly those that require moist soil conditions, such as:

• Pothos (Epipremnum aureum)
• African violet (Saintpaulia spp.)
• Peace lily (Spathiphyllum spp.)
• Boston fern (Nephrolepis exaltata)
• Spider plant (Chlorophytum comosum)
• Philodendron (Philodendron spp.)
• Orchids (Orchidaceae family)
• Rubber plant (Ficus elastica)
• English ivy (Hedera helix)
• ZZ plants (Zamioculcas zamiifolia)

These plants are not necessarily more susceptible to fungus gnat infestations, but their growing conditions may make them more attractive to the gnats.

Fungus gnats can also be a common pest on a variety of crops, particularly those grown in indoor or greenhouse environments. Some of the crops that are known to be susceptible to fungus gnat infestations include lettuce, strawberries, tomatoes, peppers, cucumbers, and herbs such as basil, cilantro, and parsley.

Fungus gnats can be a serious problem for growers, as their larvae can damage plant roots and reduce crop yields.

Regions impacted

Fungus gnats are found all over the world in both indoor and outdoor environments. They are most commonly encountered in areas with high humidity, such as tropical and subtropical regions, but can also be found in temperate regions with damp soil conditions. Fungus gnats are common pests in greenhouses, nurseries, and indoor growing environments, where they can reproduce rapidly and cause significant damage to plants.

Description

Fungus gnats are small, dark-colored flies about 1/8 inch in length. They have long, slender legs and wings often held above the body when at rest. Fungus gnats are most easily identified by their habit of flying in a slow, fluttering pattern close to the soil surface. Their larvae are small, white or transparent, and worm-like and are typically found in the soil or growing medium.

Life Cycle

The life cycle of fungus gnats consists of four stages: egg, larva, pupa, and adult.

• Egg: The female lays her eggs on the surface of moist soil or other organic matter. The eggs are very small and difficult to see with the naked eye.
• Larva: The eggs hatch into tiny, white, or transparent larvae that feed on fungi and decaying plant material in the soil. They have a worm-like appearance and can be found in the top few inches of soil. The larvae grow and molt several times over several weeks to a few months, depending on environmental conditions.
• Pupa: When the larvae are fully grown, they enter the pupal stage. They spin cocoons in the soil or on the surface of the growing medium and transform into adult gnats over several days to a few weeks.
• Adult: The adults emerge from their cocoons and fly around the growing area, searching for mates and suitable breeding sites. The adult stage lasts for several weeks, during which the females lay more eggs on the soil surface or other organic matter.

Under optimal conditions, the entire life cycle can be completed in as little as two to three weeks, making it difficult to control.

Damage and Detection

Fungus gnats can damage plants in several ways, both through the feeding activity of their larvae and through the nuisance of their adult flies.

• Larval damage: The larvae feed on plant roots and can cause root damage and stunting of young plants. They can also introduce plant pathogens into the soil through their feeding activity, which can cause plant diseases.
• Adult damage: Adults do not feed on plants, but they can be a nuisance to growers and interfere with other insects’ pollination.

Detection of fungus gnats can be done in several ways, including:

• Visual inspection: Growers can look for adult flies flying around the growing area, as well as for the presence of small, white larvae in the soil or growing medium.
• Yellow sticky traps: Yellow sticky traps can capture and monitor adult fungus gnats in the growing area.
• Soil sampling: Soil samples can be taken from the growing area and examined for the presence of fungus gnat larvae.

Early detection and control of fungus gnats are important to prevent plant damage and reduce the risk of infestations spreading to other areas.

Prevention and Control

There are several ways to prevent and control fungus gnats in the growing area:

• Soil moisture management: Fungus gnats thrive in moist soil conditions, so avoiding overwatering and maintaining good drainage in the growing area is important. Allowing the soil to dry out between waterings can also help prevent the development of larvae.
• Sanitation: Good sanitation practices can help reduce the risk of fungus gnats developing in the growing area. This includes removing and disposing of any dead plant material, as well as cleaning and disinfecting growing containers between plantings.
• Yellow sticky traps: These traps can capture adult fungus gnats in the growing area. Placing these traps close to the soil surface can help capture the flies before they can lay eggs in the soil.
• Insecticides: Insecticides can control larvae and adults in the growing area. These should be used cautiously and according to label instructions to avoid plant damage and risks to human health.
• Biological control agents: Beneficial insects and nematodes can control fungus gnats in the growing area. These natural predators feed on fungus gnat larvae and can be an effective means of control.

The prevention and control of fungus gnats require a combination of good cultural practices and targeted control measures. Monitoring the growing area regularly for signs of activity and taking appropriate measures when necessary can help prevent infestations from becoming established and damaging plants.