Fungus Gnats And How To Keep Their Population Under Control

May 25, 2023
Fungus Gnats And How To Keep Their Population Under Control

Fungus gnats are insects found in Singapore that often get confused with fruit flies since they share the same size at a glance. But unlike fruit flies, these pests primarily affect houseplants as they are attracted to the moisture of their potting soil. This is their ideal environment for laying hundreds of eggs that hatch into larvae in a matter of days and then feed on the organic matter in the soil. After two weeks, they emerge as adults and then repeat the process.

Thankfully, fungus gnats pose no health risks to humans since they don’t bite or spread diseases. But if you or someone in your household has a green thumb and loves caring for plants or flowers and even crops, they can pose a serious issue if left unchecked. Once their population explodes, their larvae begin feeding on the thin roots of plants and potentially spread plant pathogens called Pythium, which causes damping-off in seedlings.

If you find yourself with a fungus gnat infestation, prevention techniques and consistent management are key to stopping their spread. Read on to learn how to eliminate adult gnats and keep new ones from emerging.

Identifying gnats and the damage they cause

Despite reaching adulthood, fungus gnats remain small in size, ranging between 1.5 to 3mm. Their appearance is greyish-black with see-through or grey wings, long legs and antennae resembling a mosquito, and a thinner body compared to fruit flies. The larvae they give birth to have thin, transparent or white bodies with small black heads up top.

Fungus gnats typically spend most of their week-long lifespan on the soil surface of plants, but they can also be spotted flying around the drainage holes of plant pots. Since they are inherently weak flyers, they can only fly in short bursts and usually just walk along the soil. Thus, they have erratic flight patterns and are much slower than fruit flies.

Fungus gnats pose nothing more than an annoyance in small numbers, and adult gnats do not actively harm people or plants. Only when their population gets out of hand do their larvae cause notable damage to plants as they feed on their roots, which is especially bad for delicate seedlings and other young plants. As mentioned, they can also cause a specific plant pathogen that causes eventual death in seedlings.

The damage they cause will look similar to that of other root-related issues like root rot. The affected plants’ lower leaves generally turn yellow and drop off, and their growth slows down or stops altogether. In extreme cases, the plants may wilt and die out if their roots get severely damaged.

Getting rid of fungus gnats

Consistency is key when it comes to eliminating an outbreak of fungus gnats. Using gnat traps to catch is fairly simple, but it is vital to regularly refresh your traps since their adult population comes in cycles. Combine the traps below with other preventative methods listed in the following section for the best results.

1. Sticky card traps

These traps are made up of a sticky adhesive and note card and are highly effective when cut into smaller squares and placed above the soil of plants or attached to the skewers surrounding them. Adult gnats will crawl or fly onto the cards and get trapped in the glue.

Since fungus gnats are attracted to yellow colours, it is best to use yellow sticky cards instead of blue ones when purchasing some from garden stores or online.

2. Cider-vinegar traps

Cider-vinegar traps are a simple yet effective solution requiring only liquid dish soap, water, apple cider vinegar, and a small, shallow container.

To make the trap:

1. Fill the container with equal parts of water and vinegar, with the liquid solution ideally being ¼-inch deep.

2. Pour a few drops of dish soap into the mix and stir gently.

3. Put the trap at the base of the affected plants or inside the pot on the soil if possible.

4. Check the traps every couple of days to refresh the solution.

Preventing fungus gnats

1. Keep the soil dry

Fungus gnats are attracted to moist soil. Therefore, try letting your plants dry out between waterings to stop or slow down an infestation. Wait until an inch or two of the topsoil gets dry before watering again, and stretch out the frequency between waterings for as long as possible to deter gnats from laying eggs.

2. Cover drainage holes

Fungus gnats often find their way into the drainage holes underneath pots and can also lay their eggs there. If you notice them around that area, cover the holes with synthetic fabric to keep gnats from getting in or out while letting the water drain freely.

3. Cover exposed soil with sand

Some people report that using sand to cover plant soil with at least a ¾-inch layer of sand keeps fungus gnats at bay so they cannot lay eggs. If used with the other methods above, this practical deterrent can be a highly effective deterrent against fungus gnat infestations.


While fungus gnats are much less of a nuisance compared to other pests like rodents and termites, they still pose an issue if left unchecked. Hopefully, with the tips above, you now know how to deal with gnats in your home and control their population to safeguard your houseplants.

Should you need professional help to deal with an infestation of fungus gnats or other pests in your residence, don’t hesitate to call on our experts at PestClinic today. As a premier pest control services provider, our veteran exterminators have years of experience and the latest equipment necessary to efficiently and safely remove all types of pests from your property. Whether it’s regular disinfection or termite control at home in Singapore, you can rely on us for all your pest control needs. Don’t hesitate to reach out if you have inquiries or require our services.

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