Houseplant Q - black flies

[chimichangaz]

I came back from holiday mid November and noticed a few small black flies upstairs. I put sticky traps in my plants and one has caught loads of the little bastards. Photo attached - is there any chance this plant can survive or should I just ditch it? It's a Swiss cheese plant and it's been growing beautifully.

Mix water and washing up liquid and spray it liberally - kills most things.

You can save it.

It's dunk time - I quite enjoy doing this. I would take the opportunity to repot while doing this.

Get a really large container that will allow for the entire plan to be submerged. A (clean) kitchen bin works well.

Fill container with water and when near filled add washing up liquid plus some hydrogen peroxide (or just a squint of bleach if you don't have any). Then fill the rest of thr container. Don't put the detergent in earlier because if you do then your container will be 50% bubbles. You want bubbles, but not excessive amounts.

I'd do all this outside, because the container will overflow.

Next get your plant. Carefully clear all of the soil off the roots. Plunge the whole plant - roots, leaves, the lot - into the container. Add something on top to keep as much of the plant underwater as possible.

Leave it there for at least an hour. It will be OK for the day. Every now and again 'swish' the plant in the water, to keep the detergent working in all nooks and cranies.

Take it out. No need to rince, the detergent won't harm the plant or roots. Repot in fresh soil. If using the same pot, sanitise it before repotting.

You can do all of this keeping the plant in the pot if you prefer. But once you take it out, run a load of clean water through the soil and discard.

It’ll be fine OP. No need to wash the plant 😂 just keep using the sticky traps that breaks the cycle and eventually they’ll all be gone. Underwater the plant in the meantime, because the bugs love soil fungus and if that dries out they die off faster.

no need to do something drastic with the plant.
those look like fungus gnats. they are harmless, if annoying.

you can break their breeding cycle by adding pebbles on top of the plant's soil. and be careful not to overwater the plant.

Ooh loads of good advice. Because I'm lazy I will try the pebble option but thank you all 😊

Not necessarily harmless. The larvae will eat fleshy roots.

OP - if you do a search, there have been several fungus gnat threads recently

Nematodes (order from Amazon), gravel, water from the bottom.

Stop watering. Let the soil dry out literally to the point where the plant starts to wilt. The dryness breaks the flies life cycle because they need water to breed. Then you can start watering your plant again and hopefully the flies will be gone.

Agree with the above, these are fungus gnats.

Look for Steinernema feltiae nematodes (usually under the name Nemasys) on ebay etc. Be careful you ONLY get this species as other nematodes won't work.

It's counterintuitive as the fungus gnats feed on fungus, which grows on wet soil, but you have to keep the soil slightly wet for the nematodes to work.

The amount you can buy for a tenner will be enough for easily 50 plants, just keep the water agitated while applying as the nematodes settle to the bottom.

The other option are Hypoaspis (now called Stratiolaelaps) mites. Or Macrocheles mites. These again are easily enough to treat 50 pots, just sprinkle over the top of the soil. People freak out with mites as they worry they'll go to the kitchen, but these mites ONLY eat other mites and fungus gnat larvae (predators), so they're absolutely safe to use around the house.

The other option is to dry out the soil completely, but you'll risk the plant.

I've just bought a wee pitcher plant. I'm expecting it to die because I've never had a carnivorous plant before. In the interim I hope it'll take care of any gnats. I've not seen too many so far but my helpful window spider died, her replacement did turn up but he's is a different species (some kind of blanket web?) and very small at the moment, so I needed a backup plan(t).

Change the soil to get rid of any eggs