I'm dealing with a fungus gnat problem and I'm curious if I can mix beneficial nematodes with my dunk water. I've seen lots of discussions on using one or the other, but no one seems to talk about applying them at the same time. It feels like a lot of hassle to do them separately! Right now, I have a piece of the dunk sitting in my water jug overnight and the nematodes, specifically Biologic Scanmask Steinernema Feltiae, won't arrive until Wednesday. I'm just trying to find a way to tackle these annoying gnats once and for all!
2 Answers
It really depends on the type of nematodes you’re using. Some nematodes can be affected by BTI (the active ingredient in the dunk), so it's worth checking which ones you've got. Just to be safe, I’d recommend using the dunk first, letting it do its thing, and then introduce the nematodes later. Waiting a couple of weeks between applications might give you the best results without harming the nematodes.
I hear you on the frustration! Same situation here with the gnats. I usually apply BTI first and wait a week or so before introducing nematodes. It might feel like extra work, but it helps to ensure the nematodes survive and work effectively. Hope you get rid of those gnats soon!

That sounds like a solid plan! Also, don’t forget to keep the soil moist after applying the nematodes to help them do their job!