Fungus gnats: help!

[newyorkbreakfast]

Almost all my indoor plants are affected. I've tried matchsticks in the soil, cinnamon, drying the soil out, changing the potting compost.
Is there any more I can do to get rid? It's driving me mad. I was about to repot a plant... I lifted it from its decorative pot, only for there to be yet another cloud of gnats.

I've been using a spider which seemed to keep the numbers down, but she had been around for a couple of years and I think she's gone to the great web in the sky 😭.

My daughter got a plant for uni that got infested so we're trying the yellow sticky shapes you can insert in the pot. I was shocked at the number of them they've captured. She's been using them since Xmas though and there are still lots being captured, I think (like the spider) they're control rather than eradication.

In addition to the spider I've used a small pot/ramekin half filled with a 50/50 mix of water and vinegar and a drop of detergent (like w/up liquid as a wetting agent so the little bastards sink) it attracts them and they drown. Place the pot among the affected plants. I think the dregs of a glass of wine can be used instead of vinegar.

Something I've not yet tried is a mulch of fine decorative gravel/sand on top of the potting medium. Deep enough so the flies can't get through it to lay their eggs, so at least 1/2".

If it's any consolation I think they're harmless to a healthy plant but they're bloody annoying.

Thanks for that. Very helpful. I haven't tried the tape yet. I never had a problem until last spring and they seem to have spread to all my rooms since despite best efforts. Very hard to get rid of them, short of throwing all my plants away.

If it's any consolation I think they're harmless to a healthy plant but they're bloody annoying. They like fleshy roots, and can chew right through them where they meet the plant.

The swarms of flies are hatched out grubs. I use household fly spray on the flies if there are too many. Otherwise repotting as soon as I have a suspicion of an infection, and covering all pots with a layer of gravel, has got rid of the problem.

Thanks @meredint I bought sand last year as an alternative to the gravel coating but still they've gone back. Maybe I need to buy gravel.

I tried nematodes (search fungus gnat nematodes on amazon). They worked really well, nothing else had worked for me.

I use the sticky yellow tapes you stick in the pots. Seem to be making a difference. Had masses of them at first, number reducing . Fingers crossed stays that way.

I find gravel works better for me, but that’s partly because sand is easily disturbed if you water from the top.

Definitely a good layer of horticultural grit on top helps - they can lay eggs in sand I think. Gravel would work but grit might make more sense in small pots. Maybe consider a carnivorous companion plant (although I'm terrible at keeping Venus fly traps alive)

We had this once, from a plant we bought (had none previously) and put in the kitchen. They can also live down the plughole in the gunk, so had to keep bleaching and pouring boiling water down there too.

I find a dual approach works best - spray and sticky things.

Liberally spray the top of the soil with the Baby Bio houseplant bug killer spray to deal with the eggs and one of those yellow sticky things to deal with the adults. Re spray once a week until they are under control. I also put a sticky thing in plants nearby to stop cross contamination, but I only spray if the plant certainly has the gnats. Reduce watering, but don't allow it to dry out too much or the plant can suffer.

I find that once a plant has them, you never fully get rid of them, but as soon as I see one near a plant, I give it a good spray and pop in a fresh sticky thing, and they don't take hold.

Another vote for nematoads, it was the only thing that worked for me when my houseplants were infested.

Yep, we had an awful infestation recently, nematodes worked ( took about 3-4 weeks but all gnats gone now).

Yellow traps and nematodes didn't work for me. I ended up re-potting them all (just in case) but luckily I only have 8 to do. I'd only just re-potted the one that was badly infested so I think they came from the new bag of soil. Ended up buying expensive soil that was very securely sealed (Soil Ninja) and bought their gravel stuff too in order to deter future gnats.

If you can be bothered, bottom watering works. By watering from the bottom, the top layer of soil doesn't get wet so the eggs die out.
A deep ish layer of acquarium gravel at the top helps.
In the mean time the yellow sticky things are horrific but will reduce the current numbers and then with step 1 and 2 any babies will die off too.
Horrid little things. Makes me itchy just thinking about them.

Thanks very much. I'll try the gravel and bottom watering.

Have tried all the above,every single thing. Finally used nematodes and they worked. Hurrah!

For about 2 weeks. The bastard things are back yellow stickies are full. With a very heavy heart I think 8 peace lilies are about to be consigned to the compost heap which makes me sad as they have all come from splitting the original mother plant. I might try one more nematode drench but then I will concede defeat.

I use a combination of Diatomaceous Earth in the top few inches of soil and sprinkled over the plants (although it does look like someone sneezed in a cocaine factory 🤣) along with a good grind of black pepper and a cautious spray of extremely dilute washing up liquid and neem oil.
The Diatomaceous Earth is an incredible product, not harmful for pets or us. Infact buy medical grade, you and your pets can use it in your diet too!

They’re too small to trigger VFT. Drosera (sundew) or butterwort would be better

They’re not very fussy about plants, it the soil you need to be rid of, not the peace lily

Ooh! Thanks for all the advice, I've suffered from these recently.
I did the sticky traps and have just done my annual spring repotting. I removed as much compost from each plant as I could, especially the top layer, and I have isolated the worst infected plants.
I'm also trying this:
Houseplant Myst - Complete Care - Houseplant Care - Hortology

Another vote for Nematodes - the only thing that worked for me, and they're about 6.99 online.

Pretty sure they're in the compost when it comes in if I repot the plants - has anyone had any success treating compost eg. with boiling water before use? Or would that be a really crazy idea??

I ordered some lady bugs online and let them loose on my house plants. They took care of my infestation without having to use any harsh chemicals.

I tried all the rememdies above. Neem oil might have worked if I hadn't run out of patience with the mess it made and the smell, nematodes worked but they little sods come back, so need regular applications.

@Bramshott you can bake the soil in the oven before use to kill any off, It doesn't damage the soil.

I've had to put my plants outside in a sheltered spot and have covered the tops in gravel, To try and get rid of them!

Let's see what happens when I bring them back in.