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If you’re bothered by small flying insects that arrive every time you water your houseplants, you’re most likely dealing with gnats—specifically, fungus gnats.
These pests are drawn to the wet soil of potted houseplants. They require damp soil to deposit their eggs, and organic debris in the soil feeds their larvae.
This feeding activity is not only unpleasant, but it can also be harmful to your plants. In this article, we are going to discuss how we’ll identify and control fungus gnats.
What Exactly Are Fungus Gnats?
Fungus gnats, also known as dark-winged fungus gnats, are small flies in the Sciaridae family and the genera Bradysia and Ofelia.
Flying about your plants, your head, and your light sources can be irritating and make you seem dirty, but these flies are primarily a nuisance pest.
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The adults are not dangerous. Their maggot-like larvae that reside in the soil, on the other hand, can cause damage, particularly to young plants.
In the developing media, the larvae graze on fungi, algae, and decaying organic materials, but if populations are huge, they may munch on root hairs and roots.
Identification
Adults are fragile, greyish-black, mosquito-like flies (1/8 inch length) with long legs and one set of clear wings.
They are weak fliers that emerge from potted plants, particularly when watered. Larvae or maggots (1/4 inch) feature a shiny black head and an elongated, whitish translucent body.
They are particularly common in moist, fertile soils and feed on root hairs, fungus, and other organic materials.
Life Cycle
Adults have a one-week lifespan and can lay up to 300 eggs in rich, moist soils. During their two-week lifespan, tiny larvae emerge within 4-6 days and begin feeding on plant roots. Before young adults leave the soil and begin the next generation, the pupal stage lasts 3-4 days.
Depending on the temperature, the entire life cycle from egg to adult can be completed in as little as 3-4 weeks.
Potted plants can host each stage — egg, larvae, pupae, and adult — in multiple generations at the same time due to their proclivity and relatively short gestation. As a result, most remedies necessitate repeated applications until no surviving eggs are found.
Damage
Plant symptoms of fungus gnats include withering, vigour loss, poor growth, and yellowing. In severe infestations, a large section of the plants may be destroyed.
How To Spot Fungus Gnats
How can you detect if your plant has fungus gnats? After all, they resemble small mosquitos or black flies.
It’s not difficult to identify if your house plants have fungus gnats. The first and most reliable method is to thoroughly inspect the soil. If you notice black flies or insects flying around your plants, it is a good indication that you have a fungus gnat infestation.
Other methods for identifying fungus gnats include:
- Fungus Gnat Larvae should be sought out. Take a look around the area where your house plant is located. Are there any white larvae on the ground’s surface? Fungus gnat larvae resemble small white specks on the soil. These are newly hatched fungus gnats.
- Examine the plant for yellowing leaves or leaves that have fallen off. Plants naturally shed their more mature leaves to make way for new foliage. It is not normal if the plant loses more leaves than planned or if it loses both young and elderly leaves.
- Check the growth rate of any seedlings you have. Are your seedlings or young soft plants growing at a reasonable rate and progressing as expected? If they do not appear to be growing at the rate you expected, you may be dealing with fungus gnats. Larvae of fungus gnats can stunt the growth of young plants.
How To Control Gnats
When there are clouds of small flies bothering you and your plants, it’s tempting to pull out the heavy weapons, but bear in mind that you and your plants share an environment.
Whatever you use to treat them must be safe to use around you, your children, and your pets.
Fortunately, there are several safe and effective methods for dealing with fungus gnat infestations in your houseplants, they include:
1. Biological Control
Homeowners can use products containing Bacillus thuringiensis subsp. israelensis (Bti) to control fungus gnat larvae in soil (e.g., Control, Mosquito Bits, etc.). These treatments do not affect fungus gnat eggs, pupae, or adults.
Apply these products with plenty of water to assist the Bti in filtering through the soil and reaching the larvae. To control newly hatched larvae, apply several applications five to seven days apart until the infestation is under control.
2. Non-Chemical Control
As previously stated, using sticky traps can aid in the control of fungal gnats. Changing the environmental conditions of houseplants, on the other hand, is the single most important step in managing this insect.
Keep the soil surface dry to prevent the insect from laying eggs. You can accomplish this by allowing the top inch of soil to dry out before watering.
Alternatively, you can water from the bottom to keep the soil surface dry while providing moisture to the roots.
Furthermore, you can cover the soil with a 12 to a one-inch layer of coarse sand or fine gravel, which will keep the surface dry and make the soil less appealing for egg-laying.
3. Chemical Control
Chemical controls are not necessary unless the fungus gnat infestation is severe. However, if adult populations are considerable, pesticides containing pyrethrins or synthetic pyrethroids can give temporary control.
If you decide to use pesticides, use a product approved for indoor use on houseplants and read and follow all product label instructions.
Insecticides should always be used in conjunction with other non-chemical pest control methods.
Insecticides should be applied to plants and the surface of potting soil where adults typically rest.
Even in cases where the use of insecticides is justified, keep in mind that chemical treatments should not be your sole management strategy.
Is It Okay To Spray Fungus Gnats?
Biological and synthetic insecticide sprays are useful for immediate results against fungus gnats, but they are not a long-term remedy and are rarely required.
Pyrethrins, permethrin, and bifenthrin are all common alternatives. Sprays can harm beneficial insects, so use them with caution.
Spraying the soil surface and plant portions where adult gnats tend to land is a common application method.
Do Fungus Gnats Fly in Your House?
Fungus gnats are slow flyers that prefer to stay in the soil of plants or near them, though they may venture out far enough to fly near your face if you’re sitting near a plant.
They are, once again, harmless to humans and do not bite. Consider them to be fruit flies that hang out around plants rather than fruit.
Conclusion
Fungus gnats are pesky, sometimes dangerous insects that can wreak havoc on your most prized houseplants, not to mention fly in your face and against your windows.
Fortunately, there are numerous methods for controlling and reducing populations that do not involve the use of pesticides. The most crucial step is to change the environmental circumstances that encourage fungus gnat reproduction.
Have you ever seen these tiny flies in your house? Tell us in the comments how you coped with them.
