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!