Compost - fungus gnats

[newyorkbreakfast]

Following on from the other very helpful thread, I think my gnats are coming from a new bag of compost. I planted three cuttings which had previously been in water and those are now the source of these gnats.
The problem is, what do you now use for potting compost? You buy a fresh bag and have no idea whether it's contaminated with them or not. There is advice not to buy compost that's been stored outdoors but I think most garden centres store it outside. I need to drastically do something with one of my cuttings but if I repot it, I will be using soil from the same bag. (I have read up about nematodes etc as well)
What houseplant compost are people using?

I use half peat and half compost..i had bugs in my compost last year and it destroyed 2 rose plants.

Following for some ideas too. Having just got the better of them I don't want them back.

Agree it's bags of compost though

Are you in the UK? Peat is being banned for sale in garden centres from next year and for all uses by 2030. It’s an incredibly endangered habitat, and a better carbon sink than forest, so important to all of us it stays in the ground

Yes....its peat ive had for a year...i understand that. But im going to use it up.

Fungus gnats thrive in damp, mouldy situations. If you dessicate the compost (small-scale you can microwave it), (large-scale you can dry it out on a mat somewhere), you should be OK.

Steinernema feltiae (the nematode you mentioned), don't get other species, is the best for controlling the larvae. You can simply soak the compost either from the top as a drench or dunk it in the nematode water. This works very well too, but you need to keep the compost damp.

The other option long-term is Hypoaspis(now Stratiolaelaps) mites, or Macrochelese mites. These only wat pests so if you have spare, you can sprinkle the rest around houseplants.

There are plenty of composts that are now peat-free. You're just looking for something quite sandy generally with low nutrients.

Thanks @C1N1C that's very helpful.

Sorry, Loubelle - I couldn't resist the temptation to preach, expecially the bit about it being a good carbon sink.