March pest of the month: fungus gnats
13 March 2023
Fungus gnats are widespread and common propagation pests that can be very damaging.
Larvae primarily feed on fungi and dead and decaying organic matter but will feed on plant roots and stems causing damage to cuttings and young seedlings.
High levels of infestation can lead to severe plant losses, as damage from fungus gnat larvae can cause plant susceptibility to root diseases. Fungus gnats and their larvae are known to spread a wide range of root pathogens such:
- Fusarium
- Phytophthora
- Pythium
- Rhizoctonia
- and many others.
The most important management action is avoiding excess watering and constantly wet growing media.
Fertilise the minimum amount required to maintain optimal growth, pasteurise growing media and keep growing areas clean and free of debris.
If fungus gnat numbers are high in your nursery they can be managed organically using biopesticides or commercially available predators. Traditional pesticides are also available.
For more information on the biology, monitoring and management of fungus gnats refer to the new updated management plan.
If you experience a fungus gnat outbreak and/or need an identification, you can send specimens to Grow Help Australia (https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/crops/test/grow-help-australia/tests). Each year, all production nurseries receive six free pest or disease diagnostic samples.
