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Insects The Uninvited Houseplant Guests

Ask the Expert: insects in my houseplants

I’ve noticed an insect infestation in all of my houseplants (I think it started in one by a window, and has spread). The insects are small, dark, and fly. Their head is much smaller than their thorax, and they look tiny and thin. They are a bit smaller than fruit flies, almost like a flea, and though I see them flying when the plant is moved or blown on, they also crawl and run. I see them mostly on the soil surface. I can’t discern symptoms with the plants (they don’t maybe seem as healthy as before, but there are no holes in the leaves or anything).

Could you tell me:
1. what these are?
2. how to get rid of them?
3. how to prevent them in the future?

I tried taking a photo (I caught one in a bug jar), but it’s really too small to focus on.


Fungus Gnat fungus gnat

whitefly white fly


Spidermite Spidermite


  1. Kami,

    There are many insects that can attack houseplants. Spider mites, fungus gnats, aphids, thrips, scale,

    I attached photos from the Insect & Arthropod Pest & Identification handout for Southern Greenhouse Conferenes from 200 to 2004 edited by Ronald Oetting UGA/CAES/Griffin Campus. See photos above.

    I think you have fungus gnats which is shown in the first photo. These occur when humidity is high and soil is overly moist. In the greenhouse we moderate watering and aerate the soil occasionally with a light scraping using a plastic fork to prevent them. Once you get an infestation you will most likely need an insecticide to kill them.

    Does your insect look anything like the photos? If it looks like any one of the photos above the process is the same. Use an insecticide to kill them. As to the cause, any time you open a window or a door there is the potential for infestation. These insects occur naturally and survive on the weeds and plants in your yard until a lovely houseplant comes their way. Keeping your plants properly watered will help. Other than that a watchful eye is the best defense.

    Fertilome makes a product called White Fly & Mealy Bug Killer which is a liquid that you can spray on your plants to kill white flies, mealybugs, aphids and spider mites. I’m not sure how effective it is for fungus gnats. Bonide makes a granular systemic insecticide called Systemic Houseplant Insect Control. It kills fungus gnats, mealybugs, whiteflies, thrips, aphids etc. Because it is systemic the plant absorbs the chemicals and the protection can last up to eight weeks.

  2. Thanks!
    I think they are fungus gnats from the photo! I’ll follow your advice and get the Bonide product.

    Thanks for your help!

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