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| Adult fungus gnat showing the distinctive, curved “Y” fork in the wings. Photo Credit: B. Schoenmakers, via Wikipedia. |
Do you have tiny flying insects in your home? These insects don’t pose a health risk to people or animals, but they are very annoying. They can be controlled if you know which tiny flying insect you have.
Fungus Gnats
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| Photo: Amy Norwood This is an emerging amaryllis bulb with a fungus gnat problem. See the tiny black dots on the yellow paper? Those are gnats trapped on the sticky whitefly trap I’m using to control the problem. |
Fungus gnats thrive in moist soil, so the first line of attack is letting the soil dry out. Dial back on your plant watering and make sure plant trays and saucers under the pots stay dry.
Chemical controls for fungus gnats can be applied to the soil. However, if you have children or pets in your home you might not feel comfortable using these products. A child and pet-safe solution is sticky whitefly traps. These are extremely sticky pieces of bright yellow paper that are hung in the plant or placed in a small holder that goes in the soil. The yellow color attracts the gnats and they stick to the paper. Sticky whitefly traps are inexpensive and can be purchased online or in garden stores. Don’t bother trying to use yellow sticky notes as a substitute (which I have tried). They aren’t sticky enough to trap gnats.
Other Gnats and Flies
My impulse is to overwater my houseplants, and as a result I battle fungus gnats year-round. So, when I see a tiny flying insect in my home, I automatically assume it’s a fungus gnat. But, I’ve been wrong a few times and have had to do a better insect ID to effectively control the bugs.
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| Photo: Amy Norwood This is an inexpensive water meter. I use it to help me decide when my houseplants need water. Overwatering can breed fungus gnats. This meter shows that the soil is moist and that I don’t need to water though the soil surface looks dry. |
One time I kept finding dead gnats around my bathroom sinks. These, I learned eventually, were moth flies. Moth flies feed on bacteria that accumulate in constantly damp plumbing pipes, so they’ll be found around sinks and showers. Moth flies don’t live in houseplant soil, so fungus gnat remedies won’t work on them. What will work is using a brush to scrub the plumbing pipe connected to the drain where you find the bugs. Scrubbing the pipe is helpful because it removes the bacteria the moth flies need to survive. Also, drain cleaners that foam and cling to the walls of the piping are effective in clearing out the bacteria. Blasting hot water into the drain won’t solve the problem.
If you have tiny flying insects that you can’t readily tie to a source like a houseplant or drain, think of vinegar flies. Vinegar flies live in food and beverage environments. Overripe produce is a typical home for vinegar flies. They’ll also take hold in small amounts of beer and wine in the bottom of bottles and cans in your recycling bin. Finding the source of vinegar flies is the key to controlling them. Throw out the source and you’ll be rid of the flies. One summer my whole house was full of tiny flies and they were making me nuts. Finally, I found the source, a box of onions I had stowed in the furnace room in my basement and forgotten about. Bye-bye onions, bye-bye flies, problem solved!
For more help with gnats and flies in your home, check out the following CSU Extension Fact Sheets:
Flies in the Home, Fact Sheet 5.502
Fungus Gnats as Houseplant and Indoor Pests, Fact Sheet 5.584