How do I combat fungus gnats?

If you see small flies buzzing around your houseplant(s), there is a chance that they are fungus gnats. These flies, also known as fungus gnats or fern gnats, are very similar to fruit flies, but instead of targeting your fruit, they target your beloved houseplants. Of course, you want to solve this problem quickly, but it is just as important to know how to prevent fungus gnats in the future.

Preventing fungus gnats

Fungus gnats are often attracted to very moist soil and rotting organic matter. They lay their eggs in these conditions, sometimes as many as 200 at a time! It is therefore crucial not to make the soil of your plant too moist and to ensure that no water remains in the pot. Rotting or constantly wet soil is like paradise for these annoying flies. It is therefore essential to take good care of your plant and ensure good drainage in the pot.

How do I combat fungus gnats?

Have these pests targeted your houseplant? Then combating them is the only solution! Follow this step-by-step plan and your green friend will be back to its old self in no time.

If you have several houseplants together, it is important to isolate the plant with the eggs from the other plants. Not sure which plant the flies are in? Water all the plants and observe carefully which plant the flies take off from. If you cannot find the infected plant this way, move the plants further apart as a precaution.
Allow the soil of the plant to dry out and only water it when absolutely necessary. Of course, you don't want your plant to die of thirst.
Place a glass of red wine next to the plant, as this attracts fungus gnats. Once the adult fungus gnats are trapped in the red wine, they can no longer lay new eggs.
There are two ways to combat the larvae. The first is to use nematodes: these are small worms that you can simply pour into the potting soil. Nematodes are natural enemies of fungus gnats and will eat the larvae. Once the larvae are gone, the nematodes die out, solving the problem.

If you are not a fan of small worms, you can also provide the plant with fresh potting soil. This amounts to repotting your houseplant, but you simply put it back in its familiar pot. Make sure that as little of the old potting soil as possible comes along, as this reduces the chance of black fly eggs remaining.

Spread of fungus gnats

Fungus gnats spread easily over long distances, searching for suitable conditions to reproduce. This happens both through the larvae, which move to new food sources, and through the adult gnats, which actively search for a place to lay their eggs. Because they are so mobile, they can quickly reach other plants or rooms in your home, making it important to take action quickly if you have an infestation. Preventing spread is therefore just as important as controlling the fungus gnats themselves.

Help! The fungus gnats are back

It is possible that the fungus gnats will return after you have combated them, often after a while. This usually happens because the care of the plant has not changed. Fungus gnats are attracted to moist potting soil, and this is often related to the amount of water you give your plant. After combating the fungus gnats, it is therefore essential to adjust your watering regime. Water less than before and make sure that the soil can dry out properly between watering sessions, so that you prevent conditions from becoming attractive to the gnats again.