Fungus Gnat Control: How to Identify, Prevent and Get Rid of Fungus Gnats

Fungus gnats are some of the most common pests that appear at home and commercial gardens. They are tiny, but they appear in large numbers, making them a cause of significant concern. With this, it is important to learn how to get rid of fungus gnats to effectively deal with the pest and lessen the infestation that they can bring.

Even when they already grow into adults, fungus gnats are small, with most of them having a length of no more than 1/8 inch. Their body is black or medium gray. Meanwhile, their wings are light gray. They have a slender body with long antennae and legs. During their larval stage, on the other hand, they have a white body with a maximum length of ¼ inch. The eggs are round and have a clear color, which is why they are difficult to spot in the garden.

Small Adults Fungus Gnats

A Small Adults Fungus Gnats

Fungus Gnat’s Habitat

These pests thrive in locations that are dark and damp. When they are adults, they can enter the house and will be a nuisance. They fly around lights, which are annoying, although harmless because they do not bite. Fungus gnats are also common in indoor gardens or lighthouses. Outdoors, they are common in decaying vegetation and algae. Moist soil in the pot is one of their favorite places. It is the root of the plant that they initially target.

Identifying Fungus Gnat’s Damage

Plants Affected

In the garden, fungus gnats prefer to grow in foliage and bedding plants. The population is highest in African violets, cyclamens, poinsettias, cucumber, corn, clover, alfalfa, lettuce, geranium, peppers, soybeans, potatoes, and Easter lilies. These pests also love decaying vegetation and organic matter.


Here is a list of some of the most common signs that will be indicative of the presence of fungus gnats in the garden of at home:

  • The most common symptom is seeing flies surrounding sources of light, especially indoors. Some people might think that they are only black flies, but in reality, they can already be fungus gnats. They do not pose any danger to humans, but because they are often in large groups, their presence is annoying.
  • They also affect the foliage of the plant. It causes the leaves to turn yellow. This starts from the damage to the roots, and eventually, it spreads to the rest of the plant. The leaves will not only be discolored, but they will also fall off the plant and will cause severe defoliation.
  • Plant stunting is also a common symptom of fungus gnats. If the plant did not grow fully as you expect, chances are, you can attribute the problem to the presence of pests.

Results of Infestation

The larva will cause damages on the roots of the plant. As the foundation of any plant, this results in growth problems or the death of the plant while it is still young.

Fungus gnats are notorious for transferring diseases from one plant to another. Because they are flying insects, it is easy to spread the problem in the garden. Among others, one of the fungal diseases that it can bring to plants is botrytis blight, which causes the flowers and buds to develop gray molds or brown color. It can also lead to verticillium wilt. The latter is a fungal disease that causes infection upon entering the roots of the host plant.

The Plants are Spread the Fungal Diseases

Fungus Gnats Cause Brown Spots of Leaves

How to Get Rid of Fungus Gnats

Natural and Organic Solutions

Here is a list of some of the best ways to eliminate fungus gnats without the need to resort to the use of toxic chemicals:

  • There are simple traps that you can make on your own. One thing that you can use is apple cider vinegar in a clear cup. Combine it with liquid soap and mix thoroughly. Cover the top using a transparent tape, but make sure that there is a hole. Place it near the plant and it will draw the fungus gnats that are flying around. Yellow sticky traps will also deliver an effective solution.
  • A sand trap is another DIY solution that will yield a high level of success. To do this, remove the top soil of the plant, about two inches. This will allow you to get rid of the larvae that may already be present. Replace it with sand, which will help in making the surface unattractive for the presence of new fungus gnats.
  • One thing that you might not have thought of but an equally promising control method is the use of potato slices. Place raw slices side by side on the top of the soil. Replace them every day. As you lift the potato, you will see fungus gnats accumulate at the bottom.
  • You will also benefit from the use of various biological control measures, although the natural predators are not as much as what will be effective for other pests. Steinernema feltiae, a parasitic nematode, is one of the best. To deliver the highest level of effectiveness, experts recommend using at least 600 in every square meter.
  • The use of predator mites is also an effective method to control and eliminate fungus gnats. To be specific, you can use Hypoaspis aculeifer, a mite that dwells on the soil. The good thing about this is that it does not cause any harm to humans and the environment.
  • Fungus gnats can also enter the home because they are flying insects. With this, one thing that you can do is to use a screen on your doors and windows so that they won’t be able to enter. The reduction of moisture is another simple solution.

Chemical Solutions

When it comes to chemical control, it is best to use products that contain pyrethrin as one of the main ingredients. Perfect timing is one of the most important to ensure the success of this measure. Preferably, do this before the eggs hatch. When the fungus gnats are already in their adult stage, this will no longer be as effective. Other active ingredients that are equally promising include cyfluthrin and bifenthrin.

How to Prevent Fungus Gnats

Cleanliness is one of the easiest but most effective ways to avoid the presence of fungus gnats. Because they thrive in organic matter, it will be great to remove any decaying vegetation to discourage the growth of the pest. It is also important to water only at a minimum because they will thrive the most in moist environments. For plants in a pot, be sure to have proper drainage so that water will not remain on the surface of the soil.

Leave a Reply