The Plant Journal
How to Get Rid of Fungus Gnats in Houseplants
The Plant Journal · Practical plant care
Fungus gnats make enjoying your houseplants hard. But the good news is that we can outsmart these annoying little pests. Try these three approaches to get rid of them: adjust watering, catch flying adults with a light trap, and consider a suitable spray if needed.
Not sure what is flying around your plants? Read our fungus gnats vs. fruit flies guide first so you treat the right problem.
01 · Start with watering
1. Let the soil dry out
Fungus gnats thrive in damp potting mix. Give plants that tolerate dry soil more time between waterings, allowing the mix to dry as their care needs permit. Avoid keeping them constantly moist.
For plants that prefer some moisture, we are going to do the same. So, we are going to let their soil dry 100% of the way through the pot but it si very important that the day these plants soil dries out, that we water the soil so it is 100% soaked. Becasue these plants enjoy some mositure it wil be imeporative for them to get water once they are dry, so do not let the soil sit dry for more than a day.
When it is time to water, give the soil a heavy watering from a strong sourec of water. A conitnued, stronger force of water can push the eggs burried in the soil out of the pot. If you follow the waering from above, there is no need to worry about voer wateirng your plants like this.
Maryland Extension’s fungus gnat guidance explains the role of soil moisture.
02 · Catch flying adults
2. Use a blue UV light insect trap
A plug-in trap such as the Zevo Flying Insect Trap at Walmart uses blue and UV light to attract flying insects and catches them on an adhesive cartridge. A regular blue light bulb alone does not trap insects.
Follow the device’s placement instructions, keep it away from watering splashes, and replace the cartridge as directed. Check new catches over time to see whether activity is decreasing.
What it can do: Catch flying adults. It does not treat eggs or larvae in the soil, so continue managing moisture in the affected pots.
See Zevo’s product information for how the trap works.
03 · Choose the right product
3. Consider a gnat spray labeled for indoor plants
You can look for gnat sprays on Amazon or at a garden center, but check the product label before buying. Choose one that specifically lists fungus gnats, the intended application, and use on your indoor plants. A household fly spray is not automatically suitable for leaves or potting soil.
Follow the label for where to apply it, how much to use, and whether to repeat treatment. Check whether it targets adults or larvae: an adult spray will not necessarily control the stages developing in the soil. Avoid spraying the air around your plants to chase individual flies.
Sprays are not always necessary for a mild infestation. UC IPM’s fungus gnat guide explains treatment options and their limits.
Keep an eye on the affected pots
Look for less activity over the following weeks, rather than expecting every fly to disappear overnight. If the problem continues, check nearby pots and revisit our identification guide to confirm which insect you have.
