Wondering why gnats have taken over your home? For most gnat infestations, the cause is typically due to sanitation, but that doesn’t mean your home is dirty. Gnats appear and proliferate when they have access to food and breeding sites, according to Scot Hodges, vice president of professional development and technical services at Arrow Exterminators.
“Infestations can also seem to arise out of nowhere because of how quickly gnats reproduce,” Hodges explains. “Once one or two are observed, the time from laying the eggs to adult can happen in a few days, and numbers will continue to increase while breeding sites and food sources exist.” Stopping infestations in their tracks comes down to determining the root cause and simple prevention techniques.
Below, our experts explain the most common causes of gnats indoors, possible causes of a gnat infestation, and effective ways to get rid of them for good.
Common Causes of Indoor Gnats
Pay attention to where you see the gnats, as the source will usually be in that general area. Because general sanitation is the best tool to get rid of and prevent gnat infestations, most homeowners already have all the tools they need for pest control.
“It can be helpful to purchase traps to catch adult gnats, such as yellow sticky traps for fungus gnats or pheromone-based traps for fruit flies,” says Hodges. “While these do not eliminate the problem, they can help you reduce the infestation while you work to remove food sources around the home.”
Overripe or Rotting Fruit
Fruit flies, a common type of gnat, are drawn to the sugars and fermentation in overripe or decaying fruit. “They’re attracted to anything fermenting or ripening,” explains Jeremy Logsdon, co-owner of Preventive Pest Control, “so think about that bowl of bananas on your counter that’s a little overripe, the half-eaten apple your kid left under the couch, or even an open bottle of wine or kombucha.”
The Solution: The best remedy is to dispose of any overripe fruit and clean the area where it was stored. “Treatment is not generally required, and the treatment will not be effective if the food source is not identified and removed,” says Hodges. “Once the food source is identified and removed, the problem will clear up within a few days.”
Dirty Drains
Sometimes gnats and other small flies can come from clogged bathroom sinks and shower drains. “Hair that builds up in the drains can collect other materials like toothpaste, shaving cream, conditioner, and other personal care products,” explains certified entomologist David Castro. “This wet, organic material is ideal for small gnats and flies to live on.”
According to Hodges, an easy way to determine if the sink drain is the source is to place a cup or glass over the drain and leave it overnight. In the morning, check under the glass to see if there are any adult gnats present.
The Solution: To rid yourself of these gnats, the clogs usually have to be physically removed from the drains. A DIY option is to pour a 1:1 ratio of baking soda and then vinegar in the drain, cover it for 15 minutes, then flush with boiling water. “This can help to remove some buildup around the drains but might not work on more stubborn clogs,” Castro says. “Once the clog is removed, a regular drain cleaning program using an enzyme-based product can help reduce the buildup.”
Houseplants With Wet Soil
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A common source of fungus gnats in the home comes from potted plants. “If the plants are watered too often, the potting soil becomes oversaturated, leading to fungus growth on the soil surface,” Castro explains.
The Solution: Reducing the amount or frequency of watering might dry the soil out enough to solve the problem. Be sure to remove any decaying leaves or flowers that have fallen. You might also add a half-inch of sand to the top of the soil to cut off oxygen from the fungus while still allowing the plant to be watered.
“More extreme situations may require the old potting soil to be discarded and the plant repotted,” says Castro. “Additionally, make sure you empty and clean any catch trays under the plants so the standing water does not also become a source of gnats.”
Hodges suggests placing chunks of raw potato in infested plant pots, with the non-peeled side facing down. “The gnat larvae like to eat potatoes, so they’ll move from the soil to the potato, and you can easily remove them from your plant,” he explains.
Indoor Garbage, Recycling, and Compost
Gnats are drawn to the decomposition of organic waste. “Recycling bins are also a common source, especially with cans and bottles or alcoholic beverages such as wine and beer,” he says, “along with any food left in containers being saved for recycling.”
The Solution: If you notice gnats around the trash bin, Hodges recommends utilizing a tightly sealed trash bin, as well as committing to taking the garbage out daily.
Other Common Causes
Still at a loss for the culprit behind your gnat infestation? Trevor Jones, general manager at Admiral Pest Control, offers up some other possible causes of gnats in your home.
- Dirty mop or cleaning rags: Gnats are attracted to damp, bacteria-laden cloths, so wash mop heads and rags frequently and let them dry completely in a well-ventilated area.
- Leaky pipes or persistent moisture: Wet environments encourage breeding of moisture-loving gnats, so be sure to fix leaks and use a dehumidifier in damp areas.
- Pet food or litter boxes: Uncovered or unclean pet food and litter attract gnats and flies. Store pet food in airtight containers and clean litter boxes daily.
How to Prevent Gnats In the Future
Without available food sources and breeding sites, gnats will be unable to survive and reproduce in your home, Hodges says. “If the problem persists more than a couple of weeks, you may want to consult a professional for an inspection and consultation,” he advises, “although treatment will likely not be needed.”
Here’s a list of preventative steps to take to keep those food sources and breeding sites locked down:
- Pay special attention to your produce. Clean your fruit immediately to remove any pesky hitchhikers, then keep it sealed in airtight containers or in the refrigerator.
- Rid your space of refuse. Rinse your recyclables before placing them in the bins, says Jones, and take out the garbage on a daily basis.
- Perform regular drain maintenance. Make it a habit to flush all drains with hot water regularly, Logsdon suggests—especially those that aren’t used often.
- Make it difficult for them to enter. Ensure your windows and doors are adequately screened and caulked to prevent gnats and other pests from entering your home, says Hodges.
- Avoid buildup. Avoid pouring grease down the drain, Logsdon warns, and use special strainers to catch hair.
- Be specific with watering. Water plants only when needed, Jones says, and avoid standing water in plant trays.
- Fertilize with caution. Avoid excessive amounts of organic materials such as manure, blood meal, or incompletely-composted matter when fertilizing your house plants, Hodges warns.