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  • fungus gnats larva question

    I take it the real problem with fungus gnats is their larvae and whatever they do sub-surface. I had a cutting start, then stall out, and after a while, I suspected it had rotted and so pulled it out of the ProMix and saw quite a few of the glassy little wormies running up and down the cutting itself. Do they eat the roots? I've started the weekly Gnatrol regimen, will that be sufficient for control? I've been told to allow the top 2" or so of the soil to dry out completely. Just how does one do that while using Gnatrol and rooting the cutting in a humidity bin or dome environment?
    Phoenix, AZ
    Zone 9b
    Hot, mostly

  • #2
    I try not to use old potting mix but if I do I nuke it first. I use mosquito dunks in my watering pot for my cuttings and this has helped me like nothing else. My gnat problem isn't a problem anymore.
    Ryan- CenLa, zone 8a/b


    • #3
      For plants that you have already potted up, just water them with a capful of Riptide permethrin into a gallon of water. No more gnats. Period. Everyone has different experiences with figs... I tried the mosquito dunks, and the gnats just laughed at me.
      CA 9b "May you sit under your own fig tree..." This metaphor, in use since Solomon, is a wish for the receiver's spirit to know peace, for their family to be secure, and for their life to be fruitful.


      • #4
        It is a chicken and the egg thing........did the gnats cause the rot or did they simply come in to feast when WE killed the cutting with too much love IE water. I tend to believe the latter is the truth. If though you get an infestation of the gnats and these is not enough food for the larvae they will attack healthy roots so gnats are something that needs nipped in the bud. Peroxide will kill them mixed with water and add 02 to the root zone. Phyrethins also will and chemicals such as Safari. The last one is a 100% total kill and only needs done once as it stays with the plant.


        • Esteban_McFig
          Esteban_McFig commented
          Editing a comment
          I think your comment about water gets to my real concern. I have room for 32 starts in the kitchen windowbox, using the drilled-out 24 oz. clear plastic cups sheathed in same-size opaque cups and briefly topped with another ventilated clear cup (the "three-cup method"?) as the transition/chokepoint between my in-house and backyard processes. Once out the house, the top layer dries pretty rapidly and I seem to have no gnat problem at all, even with the organic ProMix right at the surface of the 1 gal containers out there. Ditto starting the cutting roots in the first place in sphagnum--no gnats then either. It's just when I move from the initials/new root/sphagnum phase and "up-cup" to the 24 oz. size and water the cutting in to the ProMix/perlite/vermiculite at 1:1:1 and set in the windowbox do I ever see any gnats, and really, very few even then. The top humidity dome cup does seem to prevent the setup from EVER drying out completely, and to this I've been adding a half-cup measure of Gnatrol solution to "drench" the top layer per the maufacturer's instructions at weekly intervals the last couple weeks. I then set the cups without their opaque sheath and dome top on a thick absorbent towel to pull as much moisture as possible out of the media cup overnight. But it seems like those cuttings without significant top growth that were treated with the Gnatrol are completely stalling out now, and a few have visibly weakened in the Gnatrol drenching phase this last couple weeks

          So I wonder whether this thread really is more about water than about gnats--my strongest growers to date (newbie here) pre-dated the gnat appearance in the kitchen window box zone and were moved outdoors beginning a month ago. Outdoors, where the top of the soil can dry out. Actually, where the entire 1 gal pot (up-pot media is straight ProMix HP) can get close to dry in 10 days to two weeks with our daytime temps here in Phx approaching the high 80's. I'm planning to water the 1 gal outdoor trees in the future by simply setting them in a kiddie wading pool (at intervals to inclde a weak fish emulsion solution), and so hopefully keep the top couple inches of soil dry-ish at all times

      • #5
        If you want to be organic, you might try covering the exposed soil surface with the fabric softener Bounce tissues with a strong odor like "Sweet Dreams". The bugs hate the intense fragrance and fly away. It wears off after a few days and the tissues have to be replaced. I did that a few days ago with the only one of my fig pots with an infestation problem. One of the tissues had blown off. It was funny to see the few flies that had returned to the exposed soil take off quickly in all directions, as if they were holding their noses.
        Mara, Southern California,
        Climate Zone: 1990=9b 2012= 10a 2020=?


        • #6
          Oh those fungus gnats..my wife is always complaining. I noticed that pro mix and coir are the way to go indoors.


          • #7
            I use the Gnatrol also. I water from the bottom until my plants go outside. I simply mix up a gallon and set each of my 32oz cups with holes in the
            bottom sides in a large pot saucer. I allow them to sit until I can see the moisture creep up about two inches or after a while I can judge by
            the weight of the cup. That generally takes care of the larvae. I use carnivorous plants and sticky traps for the adult gnats.
            newnandawg 7b Newnan, GA


            • #8
              For the majority of us this 'Fig Thing' is the continuation of interest in growing plants and using our skills to grow more and more challenging stuff. I have found that my experience rather than being a help has been a hindrance.
              I have read many post about over watering and the untimely demise of many fig. In my mind I am thinking '...well that's easy don't water so much...'

              But when we grow plants in pots out side in sun and with a good leaf cover the water demand is apparent and strong. Any over watering will run through and evaporation from pot surface and leaf surface take care of the rest.

              Our cuttings have no leafs from which water can evaporate and they have no roots to use that water. We use our 'Summer' heads and not our 'Tender winter fig cutting' heads. And then there is the increased humidity which also slows down watering requirements. Damp conditions in a closed warm environment give us fungus Gnats which thrive on the now stressed and rotting cuttings. Manage the water and you manage the Gnats

              I now use a pen with the ink part removed. I use it like a pipette. Hold it upright, dip one end in water hold my finger over the other end and lift that water to my fig. I also push it into the compost 1 inch ensuring a dry surface. This way I can really control water delivery. I have about 25 cuttings at various stages and enjoy this nurturing process.

              It all comes down to water


              Really happy with what I have.


              • DBJohnson
                DBJohnson commented
                Editing a comment
                Thank you! I am such a Dumas (pronounced in "redneck" instead of French)!!! I used a marinade injector (aka gargantuan hypodermic syringe with giant needle) to dose out 10ml of water at a time when my cuttings felt light. It never occurred to me to inject it subsurface to keep the flying demons at bay.

                Anyone have a spare brain cell I can try to root for a transplant? (Well, with my record so far this year, I'll need 8-12 cells to make sure I have some success....)

              • The Figster
                The Figster commented
                Editing a comment
                Db If we all got it right first time it would not be as rewarding as it is!
                My brain cells are infected with FMV!

              • Esteban_McFig
                Esteban_McFig commented
                Editing a comment
                I try to stick to the sub-surface watering thing once I've "up-cupped" the rooted starts to drilled-out/ventilated plastic 24 ouncers, simply by setting them in their opaque sheath cups with a little water, and for just a 5 or 10 second count, then drain for up to an hour. But as I then return the setup to its "3-cup" configuration-with the humidity dome to temporarily protect the tender young leaves--it never completely dries up. To this, I've been adding the Gnatrol "drench" the last couple weeks--from the top down. It's getting pretty wet in there. And I was planning to add the Gnatrol solution at one final weekly interval per some instructions/suggestion I read...somewhere

                Agreed that this is at least as much a water management issue as a gnat issue