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Grrrr, gnats!

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  • #1

    Grrrr, gnats!

    I seem to have a gnat problem! Initially there was a bad one as I discovered the coffee arabica that I got for discount seemed to harbour the little horrors. Ages later, I notice that I see a couple in my kitchen and one in my living room ... I use the cidar vinegar with a couple of drops of washing up liquid trap, something that worked a dream with the coffee arabica infestation, but it doesn't seem to work as well? Not unless I put it in the greenhouse and leave it. I can't work out where they are coming from; I've binned a couple of plants that failed to take or looked like they were on their way out.

    Any other tips on how to eradicate them? Would a photo of the little beasts in my cider trap help? Any traps that work? (home made or shop-bought). I have an indoor little greenhouse that houses orchids, a gasteraloe and (now only) two baby bromeliads. I thought it was the shaky bromeliad pups that might have caused it. I looked at everyone and genuinely can't figure it out.
    Tags: gnats, pests
  • #2
    Are they fungus gnats aka sciarid flies? Cider vinegar worked for a fruit fly infestation in our wormery, but the fungus gnats weren't bothered. They like to lay their eggs in moist compost, so water plants from the bottom to prevent the top layer getting wet. You can also cover the surface of the compost with a layer of sand to stop them laying eggs. Yellow sticky traps are very effective but they can also kill other insects like spiders and hoverflies. For larger areas you can get predatory mites (Hypoaspis miles) which I found to be very effective last year: one bottle treated the whole greenhouse.

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    • #3
      Here are some photographs of the nasty little beasts to help:




      (These are two separate flies, there's a few in this trap)

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      • #4
        Good suggestions above and I've tried most with some success but the only one that eradicated them totally was a layer of grit over the top of every pot to break the cycle of the adults laying eggs in the top layer of compost. It was a pain to do but they were really getting right on my taters as the maggots can kill seedlings and cuttings. My local Supermaket is a great source for fungus gnats, careful where you buy your plants.

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        • #5
          Yeah, my orchids are from the supermarket, wondering if that's where the little horrors came from. I'll see if I can get some yellow sticky traps; my greenhouses are indoors so I don't have to worry about killing pollinators!

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          • #6
            Quick update: I bought Rentokil's Sticky Fly Traps off eBay and placed a few around the indoor greenhouse, one in the dormant big chilli and one in the living room on the Dragon Tree. So far it has caught one adult that I saw flying around inside the greenhouse when putting the traps in, so that's great! I want to put a few in the common area plants as well so they don't decide to do their life cycle out there instead. It's a recommendation so far from me!

            [Note: Like I said in a previous post, my plants are indoors so I don't have to worry about spiders, bees, hoverflies or pollinators being caught!]

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            • #7
              I had an infestation of these two years ago, and they are really horrible. About a million flew out of some plants I had ordered from Jersey Plants Direct. Never bought from them again, and never will.

              I spent a hard few months basically swatting every fly I saw, and this has paid off. They are now down to just the odd one, that I kill immediately. I doubt I'll ever get rid of them completely.

              Anyway, I read somewhere recently that if you put out a tiny saucer of almond oil the flies are attracted to it, leap in and drown themselves. I plan to try this if my problem ever resurfaces.

              Anyone else heard of this/tried this?
              Mostly flowers, some fruit and veg, at the seaside in Edinburgh.

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              • #8
                So I noticed that, despite all the traps I have, I was still getting flies. I found out where the fungas gnats have been breeding. Tiny tiny tiny white maggots at the bottom of my living room plant pots and on further inspection, I see them on the soil of my monstera
                So I've smothered it in gravel to kill them, and will be disinfecting the water saucers with boiling water. I REALLY hope this helps

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                • #9
                  Bob Flowerdew always suggested hoovering up whitefly, would work for fungus gnats too. Keeping the adults down will break the cycle.
                  Mostly flowers, some fruit and veg, at the seaside in Edinburgh.

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                  • #10
                    You could also try an electronic fly zapper that uses UV to attract them, giving a satisfying crack when a kill is made.
                    We were plagued by swarms of fruit flies and the numbers now negligible.
                    Riddlesdown (S Croydon)

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                    • #11
                      Not sure on the efficacy of this but when I had a lot of little flies on some house plants and compost, a quick squirt with fly killer on the plants and compost surface seemed to do the trick.

                      edit: I tried hoovering a wasp off a black currant bush last year but if flew and stung me on the wrist and then flew off.
                      Last edited by Mark_Riga; 20-03-2020, 12:34 AM.

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                      • #12
                        edit: I tried hoovering a wasp off a black currant bush last year but if flew and stung me on the wrist and then flew off.[/QUOTE]

                        Oops! Not recommended then.....
                        Mostly flowers, some fruit and veg, at the seaside in Edinburgh.

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                        • #13
                          So I STILL have gnats and I'm honestly at my wit's end. I am going to let everyone dry out and then find another treatment. I've seen a proposed treatment that is 1 part hydrogen peroxide to 3 parts water, has that been tried by anyoen else? Would it be safe around orchids and crops like chilllies?

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