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.
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?
I also had success with sand on top, a couple cm is fine- just enough to completely cover all visible topsoil. You may also want to start bottom watering if you can and leave the top undisturbed since the sand will migrate when you top water. You may need to reapply sand periodically so get a decent sized bag.
You may need to rethink your watering schedule for a bit too, fungus gnats love wet soil. Those yellow cards can help track population, change those out regularly (another pro tip is to cut them down to smaller pieces since you’re not actually trying to control the population with the cards)