Control of Fungus Gnats and Springtails

Question:  What pesticide do you use in your regular, preventative, spraying program?  I would like something to control fungus gnats and springtails in particular.

Answer:  Since we spend most or our days working amongst our plants, we try to use toxic chemicals as infrequently as possible.  In short, we don’t have a “preventative” program of spraying.  We do use them, but only when a specific problem makes it necessary.  Fortunately, we’ve never found pesticides to be needed to control fungus gnats or springtails.

Fungus gnats are those very tiny black flies that hover around your plants and in your lights.  They’re especially common in summertime, since they easily fly through window screens.  Springtails are very tiny, light-colored, thread-like pests that can be found on the surface of damp soil or in water saucers, and can “jump about”.  Neither are much of a threat to your plant’s health, unless found in very large numbers.

We’ve found that the simplest solution is to let the soil dry between waterings.  The plant needn’t go limp but, since both these pests desire moist conditions, eliminating the damp environment will eliminate the pest.  For those using wick or capillary-matting systems to water plants, let the reservoir/mat dry thoroughly before watering.  Also, these pests, like many others, feed on decaying organic matter–meaning dead or rotting leaves and blossoms.  Good culture and regular grooming can prevent a host of potential problems.

7 comments

  • Hi!
    I am also having a gnat and springtail infestation in my 3 house plants. I have the gnats flying around my room and the springtails on the soil surface… I have tried diluting 3% hydrogen peroxide and even went with higher percentages but it doesn’t seem to help.. I literally poured it on top of the insects and they kept crawling so I guess it really only kills the larvae (which I haven’t spotted yet but I’m sure they’re lurking!).
    I have also tried sprinkling huge amounts of cinnamon on the soil but the insects don’t seem to care much about it… I am going insane with these things flying around! Help :(

    • The simplest, easiest, solution is to let the soil dry between waterings. Not to the point of wilting, but dry on the surface and a bit below it. Without the damp organic matter (the wet soil) they can’t survive. If you do this, over the course of time, they will gradually disappear.

  • My friend has an infestation of what may be springtails. There are hundreds in the watering saucers and some are still alive. They are really tiny, white and he claims to have seen them jump. I have just repotted about 60 which did not have this problem and already (less than a week) they have the same numbers in their saucers. Is there anything that can be done? Some of his plants have a serious case of wilting leaves. With a collection of over 200, they seem to be moving through all of them. If he has to throw them out, he won’t start again, it’s too depressing

    • Very easy solution….just let things dry out. Without the wet soil, they will gradually disappear.

  • Yes, a 3% Hydrogen Peroxide drench does work for killing the larvae.
    I just did it with all of my plants. Big difference! Let the top of the soil dry out first.
    Mix 1 part hydrogen peroxide to 4 parts water.
    Water with solution till it runs out the bottom drain hole.
    Let the plant drain well and top off with about a 1/2 inch of sand.
    This is what I am doing now. It prevents the gnats from getting back into the soil.
    If you have a lot of them flying around you can set out little cups of this solution:
    2 Tablespoons of vinegar =1 Tablespoon of sugar = 1 drops of dish soap and 1/2 cup of warm water. Mix until sugar is dissolved. They will go to it and drown.
    Hope this helps.

  • It’s true you can use hydrogen peroxide to kill the fungus gnat larvae? If so, how to dilute? Thank you!

    • I’m sure that would work, but we haven’t done this and wouldn’t know the dilution. Best strategy is to let the soil dry out–the gnat larvae need the moisture to survive.

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