Fungus gnats

[CarterBeatsTheDevil]

I've got a collection of cacti and succulents which I absolutely love and am very proud of. My husband has a rubber plant which developed fungus gnats (different room). He didn't want to treat them and now all the plants in my room (about 14) have fungus gnats. They all got them at about the same time so I didn't have time to isolate one in particular.

I know lots of people don't necessarily bother to treat them but when you have 14 infested plants that's a lot of tiny flies knocking around.

I've scattered diatomaceous earth in them and dried them out, but I couldn't leave them without water any longer (they'd been left for 4 weeks) and having watered them a week ago two of them are already showing signs of infestation again. They were very well drained. Is this just eggs from the last batch? Do I just keep going with the diatomaceous earth after every water?

I hear tell that a dish of cider vinegar laced with washing-up liquid and placed near the affected plants will help. Apparently the adult flies are attracted to the vinegar, they get trapped in the liquid and drown.

I've not had an issue with fungus gnats for some time, and my method is to add a drip of washing-up liquid to the watering can. A tiny amount like that does no harm to the plant but the gnats don't like it.

That sounds like a good idea. I will try it. Thanks

Butterwort (Pinguicula) with its yellowish leaves for anything which would be attracted to the yellow sticky traps

This definitely works for fruit flies, but my fungus gnats aren't attracted to it, unfortunately.

I use the yellow fly traps plus I'm currently trying neem oil.

You mix a small amount of it with water and a tiny bit of washing up liquid and use it to water the plants and as a spray.

It seems to be working but apparently it can take 5 weeks to completely get rid of them.

I tried nematodes but I have too many infested plants so it was working out to be expensive as you have to do repeat treatments. They might be worth trying for a dozen plants though as neem oil stinks. Watering day now leaves me feeling queasy but the smell does wear off quickly.

Nematodes worked for when I had an awful infestation. I only needed one treatment.
i also wrapped the plants in clear bags and sealed them with the sticky yellow things so the gnats couldn’t escape, then took the bags off a few weeks later.

Thanks..I will get some of those nematodes I think. The problem is the little buggers flying round the house..they've spread everywhere and don't get attracted to the traps unless they've hatched out and the trap gets them straight away.

I don't how good it is in real life but I saw a plant TikTok where someone used a plug in fly trap that somehow attracted insects to it. It seemed to trap loads of flies.

I've just started a new round of neem oil treatment and a lot of yellow fly traps. Hoping this works!

Cinnamon isn’t as effective as the internet claims although it makes everything smell like Christmas! I repotted and then topped with vermiculite, and watered by sitting pots in the bath for an hour. Noticeable reduction but not completely fixed.

Cinnamon is completely useless! But, as you say, it makes the house smell nice.

You can treat all the pots with one round of nematodes. Then wrap the plants in cling film/clear bag to catch any of the little ones that try to get away.
the cling film or bag also then stops the free flies getting back in for a few weeks so it enabled me to completely break the cycle.
I think the nematodes only work on the larvae before they turn to flies.

Nematodes worked a treat for me. I did two treatments, a few days apart, and haven't seen them since.

Thanks CointreauVersial
Can I ask how much of the nematodes did you use in how much water? I'm awful at working out quantities! Thanks

PeppaPigStinks
Thanks for the tip. Good idea to wrap in a plastic bag to catch the little buggers that escape! The Nematodes have arrived today. It's a tiny bag but mixes to make 5 litres. Do I just water each pot like normal but with the stuff mixed in? Just not sure how much to use.
Thanks 😊

I used nematodes on all my plants today. I have a LOT of houseplants and about half are infested. I'm at my wits end with them and am tempted to bin my collection.

30 years without them and now they're everywhere.

Just to give you hope - the nemotodes worked on my 2 infested plants so fingers crossed they'll work on yours.

On watering, I’ve bought plastic watering bulbs. You fill them and stick them into the soil and it drips into the roots. Means you don’t have wet soil on top and it’s supposed to let the plant draw the water from the bulb as it needs it.

and yellow sticky things. As a PP commented they are grimly satisfying.

I haven't noticed any change in the amount of flies today.. but it's only been one day. I have yellow stickies in my plants and although they don't seem to be catching any today the little critters are still obvious on my windows and around the house.

I'm seriously thinking of taking them all outside tomorrow and blasting them with a can of fly killer

I also used the nematodes which worked - a few of my pots were really infested but one lot of nematodes did every pot plant in the house just in case (I have a fair few). As other posters have said you still need to kill the flies.
I've only ever watered from below now and they've not come back 🤞

I tried everything for a fungus gnat infestation in peace lilies. Everything mentioned above and more.
The yellow stickies are good at catching adults but the only thing to break the cycle were nematodes. Two doses did the trick and saved 12 peace lilies from being composted.

I wonder if I should order more nematodes and plan a second dose regardless.

What gap did you leave between doses?

I control the flies with RoseClear sprayed on the surface of the compost. Repeat every fortnight for a while. I catch the flies with the vac extension hose when I can be bothered.

The nematodes feed on the larvae. They won’t affect any flies that have already hatched. It may take a time for the reduction in larvae to feed through to a reduction in flies.

I took a tip further up threaf and put a carnivorous plant next to mine.

They’ve all gone.

I went to war with them last month as they were everywhere.

1. bulk order of sticky yellow things - 3 per pot- looked so grim but worth it
2. nematodes in watering regime- second application seemed to make a huge difference
3. pea gravel on top of soil of all plants

They are basically gone- will nematode again just to be sure.