Houseplant gnat infestation and pregnancy

[Eleano]

Dear Mumsnet,

I don't know what to do. I've had a fungus gnat infestation that started from one of my houseplants and has spread around to another 2 plants (I think) which means every room that has a plant in my house (most rooms) has these gnats flying around.

My DH sprayed them with insecticide a few months ago but of course the next generation of eggs still hatched.

I've also tried sprinkling all the plant pots with baking soda and watering them which kept them at bay for a couple of weeks but as soon as I watered the plants, swarms of new gnats appeared (they like the damp).

I went on eBay and bought some mosquito dunks which are toxic and you dissolve them in water with which you water the plants which kills off the larvae and eggs but I need my DH to do it since I'm 32 weeks PG and I probably should stay away. My DH is reluctant to put the plants in danger by leaving them outside in the garden shed or in the garden (as some might not fit in the shed) to let the toxic dunk components dissolve outside the house rather than indoors (since I'm PG) but I'm thinking that this should be the last chance the plants get before they get binned as I'm done with having gnats flying all over the house and fungus ones at that (meaning they live under the soil and could be carrying toxoplasmosis?). Anything you leave unattended will have a dead gnat floating in it.

It's a shame as we have a beautiful collection of house plants that are all otherwise healthy and took years to build up and I can't believe it's come to this.

P.S: I don't have any spare rooms where I can quarantine the plants as every room is either used or will be used once DC arrives.

I bought some sticky things that I poke into the plant pot and they just stick to it and die. It’s really gross, but if your houseplants are big enough, you won’t see them! It solved my problem with the same, I’ll try and find you a link….

There are definitely non toxic ways to resolve this.

First thing is - you need to stop the top layer of the soil getting wet as that’s where they Iive, so you need to water only from the bottom of the plant.

You can also block them from being able to live in the top layer of soil by covering it with a layer of something - I’ve used tiny pebbles that are for fish tanks or crushed up shells - https://marshallsgarden.com/products/crushed-welk-shells-large-11kg-10909297?variant=41308343304243&currency=GBP&gad_source=1&gclid=CjwKCAjw_LOwBhBFEiwAmSEQAe58xxxoRATqUfH0xfq6KnS5BsFqlLIdLWwKRHJC0PTY3X--u_oBERoCGFMQAvD_BwE&gclsrc=aw.ds

While that is working you can catch (and kill them) with sticky traps - gross but non toxic - https://ladybirdplantcare.co.uk/products/sticky-traps

Keep going with these things for a few months and they will go.

These weren’t the exact ones but they were similar, and like I said, effective for my situation https://amzn.eu/d/1ZYyc3O

Agree with Marfs10.

I had the same gnat issue. Stuck one of these yellow stickers in each pot's soil and instant severe reduction. Have to go through a few egg cycles, but the stickers work (and quickly)

the tiny pebbles work, I bought a packet of small stones from the garden centre and it's really worked. just cover the whole top of the soil with them.

Placemarking as have the same issue.

First change the soil, then sticky tag things then spray any remaining gnats with washing up liquid solution. They don't require a toxic response just a bit of work to clear up.

I had this and there were bastard fungus gnats EVERYWHERE. I read up on various methods and tried lots; these were the two that worked:

1. The yellow sticky traps as recommended by previous posters. https://www.amazon.co.uk/gp/product/B07R6M34HW/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
2. This nematode treatment. https://www.amazon.co.uk/gp/product/B00BBF9FGS/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1

The sticky traps made a lot of difference, but what really killed them off was the nematode treatment. I used it a few times according to the fungus gnat lifecycle (you won't need a whole packet at once just for houseplants in pots. Keep it in the fridge for up to 2 weeks, or maybe slightly longer). As far as I know it's harmless stuff unless you're a fungus gnat, so should be fine for pregnant people.

Agree with the nematodes - harmless to you, get rid of the gnats.

I used all the methods above, except the toxic one the OP mentioned. Yellow stickers, cover the top of the soil, bottom water only ... When I added the nematodes to the regime the fungus gnats vanished.

Yes, the nematodes were the real gamechanger.

The other methods (even the sticky traps) just work by cutting down the numbers, and with luck and persistence I can see you might manage to get rid of them completely - but it only takes one of them to survive and they can lay tons of eggs and start the whole cycle again. Whereas the nematodes seem to just zap the bastards.

Thank you! I've ordered the nematodes and I've already been using the yellow sticky traps but they haven't prevented new gnats hatching. Keeping fingers crossed for the nematodes.

Did you water them with the nematode water from above (wetting the top of the soil) or from below (sitting them in the solution)? The instructions say "try to keep the soil dry so water from below" but I'm going to have to repot my plants first (since we're buying pots with better drainage today) and I don't know if freshly repotted plant roots will reach the water if it's soaked through from under the pot?

Change the soil, gets rid of the eggs that are already there

I watered the plants thoroughly from above. I don't know whether this was the best way of doing it, but it worked for me. I mixed the nematode solution stronger than the instructions said (there were plenty of nematodes in the packet for a much larger area than I needed to cover). I treated all the plants in the house, not just the ones I knew had fungus gnats.

I still saved quite a lot of nematodes for a second and maybe third treatment according to the lifecycle of the fungus gnat larvae (can't remember how long this was now). Not sure whether the second/third treatment was even necessary - the flies seemed to disappear after the first treatment. But like I say there were loads of nematodes, so no reason not to re-treat.

Good luck!! It should work really well.