[E. Vinje]

Katharine –

Bt-i, the active ingredient in your mosquito control and our Mosquito Bits, will not kill beneficial nematodes. However, using both together may be a bit of overkill — both attack the fungus gnat larvae that are feeding on the root hairs of your plants. I would recommend adding Yellow Sticky Traps to reduce the number of egg laying adults and some sort of mechanical control — Diatomaceous Earth, Gnat Nix — to reduce activity on the soil surface.

As for one product to kill spider mites, thrips, fungus gnats and whiteflies, I recommend MET52. It comes in a liquid concentrate for foliar applications and a granular for for use in soil. The link below will provide more detail on how to get rid of fungus gnats and the products mentioned here.

https://www.planetnatural.com/pest-problem-solver/houseplant-pests/fungus-gnat-control/

Good luck!