I have a fungus gnat problem with my houseplants, I’ve kept them relatively under control using Mosquito Dunks in my watering can since August and some yellow sticky traps but I can’t seem to eradicate them. I was considering buying nematode pot poppers but I’ve never used them before so I was wondering if anyone had any tips for application. All my plants are still relatively small so I don’t have many large pots for any of them (most are between 4-10").
Any and all recommendations welcome, having pests is really taking all the joy out of having plants. I’m in Canada so a lot of pesticides aren’t available to me.
UPDATE: I figured I’d update this post incase someone comes looking for solutions and sees this. I ended up going with a top layer of silica sand (2-4 mm in size) on all of my pots. I continued with the BTI water, let my plants completely dry out between waterings, and bottom-watered most of my plants. I haven’t seen a fungus gnat in about 2 weeks so I think I have been successful in eradicating them. Will update again if this changes.
Update 2: I take back the update, they’re still here… I’m so over the freaking gnats.
Update 3: Just updating this post in case someone stumbles across it looking for answers. What worked for me was switching most of my plants to semi-hydro and I now have a Pinguicula Morensis that eats any stragglers that come in with any new plants. The plants that are still in soil are watered so rarely that the gnats are not really an issue.
Nematodes, 100%. Went from clapping flies around me every 2 minutes to nothing, absolute godsend.
Order them online for around 20 dollars, follow the instructions and mix it in when you water them next. They eat the fly eggs or something, whatever it is it works within a couple of days and lasts a long time. I do this whenever the flies start coming back, maybe every month or two, and after a round of repotting because of the new soil.
I also cover the tops of pots with tape facing down which helps restrict access to the soil and some of the flies will stick to it, but I will try the sand layer instead of that now based on the suggestion above.
I hope this helps, I tried a lot of things before I found this and feel your pain!
Ugh, bane of my life! I found diluted hydrogen peroxide worked, though you need to make sure you’ve got good drainage because after killing everything it leaves the soil very damp which is ideal for any survivors. Quarantining the infested plants in a separate room and not watering them helped, though this was with cacti so they managed to survive the drought!
This may be a bit of an unusual recommendation, but I’ve found biological warfare to be the best solution for fungus gnats: Drosera capensis, Cape sundews, are like nature’s bug vacuum.
There is a bit of time waiting for the plant to get ready to go, maybe a month to six weeks, but they require virtually no care aside from ensuring they’re in a bath of water at all times, and they absolutely EVISCERATE gnat populations. I used to have a terrible problem with them until last year when I got my first D. capensis, and roughly counting, one plant in a month caught over 170 bugs. They’re super fun to own and their colors are dazzling.
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Thank you for the recommendation! I’ve definitely considered carnivorous plants. Actually I ended up throwing all my plants in water last month (except for some succulents which weren’t part of the problem) to convert all of my plants to a semi-hydro system instead. I haven’t seen a fungus gnat since! Once it warms up outside and I can rinse off the substrate with a hoze I’ll be potting them up in a soilless mix.
I had the same issue w being unable to eliminate them entirely for ages. Putting a layer of sand over soil in pot was what finally completely resolved it for me (in addition to continuing all the other stuff you mentioned).
I’ll give it a shot! How thick of a layer? Like a cm or 2?
A comment I read spoke of getting carnivorous plants to help, and now I like having gnats around to feed them! I have three sundews and they capture a lot of gnats.
Bottom watering and a layer of d. earth on top was the only thing that solved it for me.
