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Fungus gnats are a common pestamong houseplants.
Their larvae feed on fungi and organic matter in our potting soil and nibble on plant roots as well.
As much as we’d like, they don’t go away on their own.
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Fortunately, fungus gnats are more of a nuisance than anything.
And they are easy to control.
Learn how toget rid of fungus gnatsand apply these strategies to avoid having problems with them in the future.
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What Are Fungus Gnats?
Fungus gnats are small flies that infest soil, potting mixes, and other media.
The adults look a bit like mosquitoes, though plumper, with antennae that are longer than their heads.
They grow to 1/16- to 1/8-inch long and have light gray to clear wings.
The adult flies are also attracted to light, so you might first notice them flying near a window.
The larvae are thin maggots, with a shiny black head and long, whitish-to-clear, legless body.
When present in large numbers, they can damage roots and stunt plant growth.
This throw in of damage is rare in the home setting.
Feeding damage often presents as wilting, which can be hard to differentiate from other plant stresses.
What Causes Fungus Gnats?
Fungus gnats are ubiquitous, and often enter the homeon new houseplants.
They are present outdoors, but do not cause problems in the garden setting.
As such, these pests are most noticed during the fall and winter.
Managing soil moisture is among the primary methods to control and avoid problems with fungus gnats.
How To Discourage Fungus Gnats
The most effective control methods target the larval stage.
The single most important step in managing fungus gnats is altering the environment within houseplant containers.
Adult fungus gnats lay their eggs on moist soil.
Bottom watering also works well, providing ample moisture to roots while minimizing surface moisture.
Covering the soil with a 12 inch of coarse sand or fine gravel can also discourage egg laying.
When To Use Insecticides
Insecticides are only a temporary measure and generally not recommended for home use.
However, it’s safest to move your plants outdoors before spraying the foliage and soil.
For large infestations, use a biological control agent instead.
The bacteriumBacillus thuringiensissubspeciesisraelensis, commonly called Bti, targets larvae of flies.
you might find Bti products such as Mosquito Bits and Gnatrol at nurseries and garden centers.
To apply, mix the Bti with water and then drench the soil.
Though derived from a bacterium, Bti is not a living organism and does not persist indoors.
Always follow label directions for utility rates and frequencies.
How To Use Traps
Fungus gnats can also be managed to some extent through trapping.
Yellow sticky cards, available at nurseries and garden centers, are used to monitor pests by trapping adults.
As such, they also reduce fly populations.
Note that vinegar-based traps commonly used forfruit fliesdo not work for fungus gnats.
Larvae of fungus gnats can be trapped using chunks of raw potato set cut side down on the soil.
Remove and replace the potato chunk every few days to slowly trap fungus gnats.
Dispose of infested chunks in an outdoor trash bin.
How To Prevent Fungus Gnats
A good pest management strategy always begins with prevention.
As mentioned above, fungus gnats thrive in moist soils where their food sources are abundant.
Adults are attracted to the scent of decaying organic material, which promises a good egg laying site.
you could limit fungal gnat infestations by managing soil moisture and using potting mixes low in organic matter.
Begin with a healthy growing medium.
Select containers with adequate drainage and fill these with a well-draining, pasteurized potting mix.
Media with perlite, sand, or other materials to improve drainage are ideal.
Avoid potting mixes with uncomposted organic matter, such as manure.
Prevent extra potting soil from becoming infested by storing it off the ground in a closed container.
after you grab your plant potted up, take care not to overwater it.
If plants are infested, treat them before placing them near other houseplants.
University of California Statewide Integrated Pest Management Program.Fungus Gnats.
