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.
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.
https://highlandmoss.com/wp-content/uploads/2022/03/IMG_3733-scaled.jpg
https://preview.redd.it/because-fungus-gnats-carnivorous-plant-haul-v0-8k97rhklvalb1.jpg?width=1080&crop=smart&auto=webp&s=2bfdad871281b204f19eec0985141d261ec6f156
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.