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Introduction to Fungas Gnats

Dealing with pests in your gardens and landscapes can be a challenging task, but with the right information and strategies, you can effectively manage common nuisances like fungus gnats. In this comprehensive guide, we’ll walk you through the identification, damage assessment, life cycle, and management of these tiny, yet potentially troublesome, insects.

Identification: Fungus gnats, belonging to the Orfelia and Bradysia species, are delicate-looking flies resembling mosquitoes. Distinguished by their slender legs and long, segmented antennae, adult fungus gnats measure about 0.16 to 0.32 cm in length. Recognising these pests is crucial, especially given their potential to become a nuisance indoors.

Damage: While adult fungus gnats are not harmful to plants or humans, their larvae can pose a threat. These larvae, when present in significant numbers, can damage roots and stunt plant growth. In severe cases, root damage may lead to plant death. It’s essential to distinguish between wilted plants caused by root damage and those affected by other factors like improper watering or soil conditions.

Life Cycle: Understanding the life cycle of fungus gnats is key to effective management. With four stages – egg, larva, pupa, and adult – fungus gnats can complete a generation in about 17 days, depending on temperature. Larvae primarily feed on organic matter in soil, creating shiny trails on the surface. Warmer temperatures accelerate their development, leading to overlapping generations.

Management: To control fungus gnats, focus on their immature stages rather than targeting the short-lived adults. Implement the following strategies for effective management:


  • Visual inspection for adult gnats.
  • Check for excessively moist conditions and organic debris.
  • Use sticky traps to monitor and trap adults.

Water & Soil Management:

  • Avoid overwatering and ensure good drainage.
  • Allow the soil surface to dry between waterings.
  • Eliminate standing water and fix leaks.
  • Improve potting mix drainage.
  • Minimise organic debris around plants.


  • Use sticky traps or raw potato chunks to trap adults and larvae.

Biological Control:

  • Employ naturally-occurring biological control agents.
  • Consider Steinernema nematodes, Hypoaspis predatory mites, and Bacillus thuringiensis subspecies israelensis (Bti).
  • Maintain natural enemies like predatory hunter flies.

Chemical Control:

  • Reserve insecticides for extreme cases.
  • Prefer Bti or Steinernema feltiae nematodes.
  • Use pyrethrins or pyrethroid insecticides with caution.

Conclusion: Managing fungus gnats requires a holistic approach, focusing on prevention and targeted control methods. By implementing these strategies, you can protect your gardens and landscapes from the potential damage caused by these small yet troublesome insects.