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?

That's great thanks mere
I used nematodes and after the second dose, I've only seen one fly which I hope we killed before it got to lay eggs. I watered the plants again.and not sure if that was a good idea just yet as it might have washed out the nematodes. I highly recommend the nematodes anyway.

Sticky yellow things and NEMATODES - a good big strong dose through your plants AFTER you repot them. Make sure to shake out as much of the old soil as possible

My first infestation came from a bag of compost, I’m sure of it. Had to throw out a number of plants.
second infestation the nematodes sorted it

I put a couple
Of CMs of sand on top, it prevented the larvae from coming up/new eggs being laid and put a stop to the cycle very quickly. Would do it again.

Good luck!

Thanks all! This is really helpful

I've just repotted the houseplant I think is worst affected, a peace lily. I didn't see any grubs but interestingly the root ball was still the size & shape of the previous pot it had been in. The soil was quite wet & stinky. I've rinsed most of the old soil away as I think the fungus gnats came into the house on the compost I used previously. I'll try to keep it drier. 🤞

Yeah, that’s a nuisance thing. The plant gets potbound at the nursery, then when you transplant it, the roots don’t go exploring the new soil, and of course the soil gets wet and stinky because there’s no life in it.

I take the old advice and tease out the rootball and spread some of
the roots out, encourage them to grow outwards. More recent advice for planting out shrubs is to make vertical radial cuts into the rootball. I’ve never tried that.

there’s also suggestions that square pots are better because the roots gou out into the corners instead of round and round

On a similar note, I once heard that you should plant trees & shrubs in a square hole, with very defined corners. If you make the hole round, the roots just stay in the softer soil where you've dug it; if the hole is square, when the root reaches the corner, it will keep growing in the same direction and push through into the firmer soil.
Don't know how true that is. 🤷‍♀️

I think my situation has improved.

I repotted a few plants, I'm only watering from below with neem oil and then, based on someone's advice on here, I went for the nuclear option and used fly spray on the top of each plant.

There are so many yellow sticky things around that me and the cats keep getting caught on them but it does seem to be working!

There are so many yellow sticky things around that me and the cats keep getting caught on them but it does seem to be working!

Same here, only they stuck to the curtains!
and DS's cuddly penguins!

Fungus cats!

😂that would be amazing!!

Thought I had won this war after I deployed the nematodes but the bastards are back! All the peace lilies in the office affected again! Grrrrr
Another round of nematodes called for. Nothing else has any impact at all

@Hedjwitch I started another post on the dreaded fungus gnats last week! Not yet tried it but someone recommended covering the top of the soil with decorative gravel. Worth a try?
The thing which is (fingers crossed!) improving my situation is watering from the bottom.

Good luck!

Mine are back too. I've done the gravel and watering from the bottom and that made it better but didn't get rid of them completely.

Back to the nemotodes for me too

Gravel, and watering from the bottom to keep the top dry, isn’t an instant fix. It won’t of course kill any flies which are climbing up and down the pots, and it won’t kill any larvae in the soil, who will still emerge in due course. What it will do is deter any flies from laying eggs for a new generation.

They're back!! I have used nematodes (2 doses) and it worked for a few weeks. Since we brought in a Xmas tree in a pot, they're back. 😡So back to the nematodes it is!

Mine responded to the washing up liquid. Haven’t seen them for about 3 weeks

They'll be back. They need to be kept on top of those buggers. I don't think there is a one time fix solution anymore.

I've given up and switched to fly spray as someone advised on here.

I only water from the bottom so the top of the soil is never wet and then as soon as I see a fly I give ALL the plants a blast of fly spray.

I have about 40 plants, the nematodes weren't working well enough and the neem oil smell makes me queasy!

So far, no resurgence. Stickies all clear. I took a huge leap of faith and added a Middle of Lidl Christmas Cactus to the fold a couple of weeks ago; still fine. (The new arrival has settled in beautifully, but needs a pot.)

I'm all clear too. I did give a couple a blast of flu spray because I saw ONE near them but otherwise 🤞🤞

I have drastically reduced watering as I do every winter so I'm sure that's helping too

My plants don't have flu or flies now 🤦🏻‍♀️

FLU NEMATODES

I have also reduced watering and am slightly anxious that the bastards will turn up again as soon as I water (though I'm fully armed with bottom watering plus gravel per @MereDintofPandiculation 's recommendations)

ooh interesting thread! I am a recent owner of houseplants and had some fungus gnats in a small collection upstairs only. I used the Plant GP tablets as linked by a pp, decorative gravel on top of the pots, and the yellow sticky things. I also repotted the affected plants as I think it came from some plants I got from someone else. these measures seemed to work well upstairs but then I discovered some in one pot downstairs too! but it didn't have gravel in. I am going to try bottom watering only and going a bit further between watering and the washing up liquid too.