Flies in Houseplants: How to Identify & Treat
You’ve purchased a couple of beautiful houseplants and invited some guests to show them off. How exciting!
But wait! Your show may become an embarrassment as one of your guests looks at your plants and finds a bunch of bugs flying around. Ew!
These flies are called fungus gnats and are a common problem for houseplants. Luckily, there are treatments and preventative measures to keep your houseplants free of these pests.
Read on to find out what fungus gnats are, how to identify them, the methods of treatment, and the preventative techniques to use to keep them away.
What are Fungus Gnats?
Fungus Gnats are tiny, winged insects found around the soil of houseplants. They are 1/8th of an inch and appear dark brown or black. They also have long legs and translucent, dark wings.
You’ll find these insects hovering around your soil because this is the part that interests them. They don’t care much about the leaves of your plant. Instead, they lay eggs at the surface of damp soil and feed the root hairs of your house plants.
So why are they called fungus gnats? These insects are so-called because the offspring in some families feed on fungi.
The larvae (maggots) look like pale worms with a black heads. They are tiny, only 1/4th of an inch, and feed on your houseplant’s soil (organic matter and fungi).
Fungus Gnats VS Fruit Flies VS Drain Flies
It’s common to mistake fungus gnats with fruit flies. However, you must know which fly you’re dealing with, which will help treat and prevent them.
When you see one flying around, you may confuse a fungus gnat with a fruit fly. However, observing a resting one may help you identify the type of fly you’re dealing with.
Fungus gnats don’t fly very well, for starters, and you may see them run across surfaces as you approach them. But, on the other hand, fruit flies take to the air at the slightest chance of danger.
Another difference is that fungus gnats have black eyes, whereas fruit flies have bright red ones.
You may also confuse fungus gnats with drain flies. Drain flies have a moth-like appearance (also called moth flies) and are heart-shaped. In contrast, fungus gnats are long and thin like a pill.
If you cannot distinguish by appearance, you can tell the difference by observing where the flies are frequently found. Fruit flies are attracted to food and decaying matter and therefore are found around food, garbage disposals, and sink drains.
Drain flies are normally found where there is moisture and organic matter.
Fungus gnats like to hang around plants and places with organic matter.
So why must we get rid of fungus gnats? Adult flies won’t bite you or damage the houseplants. However, having flies around is a nuisance and kills the beauty of your plants.
The adults may be safe, however, the larvae are not. The larvae can damage roots in large numbers, leading to stunted plant growth. This is more common in young plants and seedlings. In some cases, significant root damage may lead to plant death.
Most cases of damage occur in nurseries, greenhouses, and sod farms. Therefore you don’t have to worry about fungus gnats when it comes to houseplants. However, elimination and removal are necessary to keep your home pest-free.
How to Diagnose Your Houseplants
Think your plants have got fungus gnats? Here are a few ways to tell.
Since fungus gnats won’t cause any significant damage to your houseplants, you can’t rely on your plant to display any symptoms, particularly at the beginning of the infestation. Instead, you’ll have to identify the fly yourself, which is easy to do.
In addition to the physical description discussed earlier, fungus gnats stay close to the plant, flying about in a zig-zag motion. They may also be present close to light sources.
Unlike other flies, fungus gnats walk on surfaces that may help you identify them easily.
Since this insect multiplies fast, you’ll likely see different bug stages at once. You can spot the larvae by gently stirring the soil.
Although bug activity typically decreases in the winters, some populations become active during this time, and fungus gnats are one of them. In addition, plants become dormant during winters which means they use less water from the soil.
This causes the soil to stay moist for longer encouraging root rot and fungus growth, making it an ideal breeding ground for bacteria.
In addition, our homes can offer protection. It’s warmer, brighter, and more humid than the outdoors, attracting these pests.
Ways to Eliminate Fungus Gnats
Want to free your houseplants of these nasty fungus gnats? Here are several ways you can do so.
This method is a great way to monitor and catch fungus gnats. Cut pieces of sticky traps and place them close to where the bug activity is the highest. You can either purchase these sticky traps or make one at home using the following steps.
- Color both sides of a 3×5 index card using a highlighter. This is to attract the gnats to the card.
- Attach it to a stick or rod.
- Layer both sides of the card with a thick coat of petroleum jelly.
- Place the cards where the bugs are.
Alcohol and Vinegar Traps
You can make this drowning trap at home to kill fungus gnats. You’ll need a shallow container (as big as a tuna can) and pour in apple cider vinegar. You can also use alcohol if you don’t have ACV.
Make sure not to fill the cup. Fill about ¼ inch. Add a few drops of dish soap and stir. Next, cover the container with a plastic wrap and secure it with a rubber band. Then, poke holes in the wrap using a toothpick.
If you want this trap to work faster, you can add a piece of fruit that’ll protrude above the solution.
Place this trap near where the bugs are and let it do its work.
Fungus gnats are attracted to the fruit and fermented liquid to lay their eggs. Normally, they can walk on water, but the dish soap in the solution breaks the surface tension preventing them from doing so.
The flies, as a result, fall into the solution and drown.
Once you have captured enough flies, throw the liquid away and make a new one.
If you’re looking for a biological control to control the pests, introduce nematodes to your soil.
Ugh, more bugs? We know it sounds counterproductive, but actually, it will kill these annoying fungus gnats.
Nematodes are microscopic roundworms that actively hunt down maggots. Once located, they move into their body cavity through natural openings (mouth, breathing pores, etc.) and release bacteria.
This bacteria causes blood poisoning killing the larvae and pupae within 48 hours of infection.
This is an excellent method to immediately kill the larvae on your soil. Mix one part hydrogen peroxide with four parts water. Transfer to a spray bottle and directly on your soil. The larvae are killed on contact.
This is another natural remedy you can use against fungus gnats. Create a solution by diluting the oil with water and spraying it on the soil.
If none of the aforementioned techniques are working for you, or if the infestation is too excessive, it may be time to consider using pyrethroids. A pyrethrin-based spray penetrates the fly’s nervous system paralyzing and killing it.
When using an insecticide, make sure you buy one labeled for indoor use to keep yourself and your family safe from any harmful vapors.
If you’re looking to avoid fungus gnats or don’t want them coming back on your houseplants, here are a few preventative methods for you to try.
Moist soil encourages fungi growth, which attracts fungus gnats to lay their eggs. Ensure the compost is fully dry before watering the soil to prevent the development of larvae.
Commercially sold compost is normally sterile, so you don’t have to worry about being contaminated with fungus gnats larvae. However, to ensure things stay that way, cover the top layer of the oil with ornamental glass pebbles, gravel, or grit.
Since the flies lay their eggs at the soil’s surface, removing that access means they won’t have anywhere to breed.
If you have a tray underneath your planter, empty it immediately after watering to reduce moisture. In addition, run the humidifier less often to reduce humidity.
You can also reduce water by watering your houseplants the right way. When you water your plants from the top, the top of the soil stays moist. So instead, water your plants from the bottom by using a cachepot or drip tray to keep the soil’s surface dry.
Regularly prune your plants and remove any dead or dying foliage. This is organic matter that larvae and adults love to feed on in the soil.
Remember, the less the decaying organic matter, the less food for these flies.
Plants are lovely creatures that deserve all the love and care they can get. This includes keeping them pest-free. We hope this article has helped you understand what fungus gnats are and has prepared you enough to deal with them.
Remember to do your research and use the best method that suits your houseplants.