Hi everyone! I'm new to this forum but I've been taking care of my houseplants very well for a few months now. By some reason I still haven't identified, one of my newer houseplants I brought home must have had fungus gnats. The infestation has practically spread to all of my plants at this point.

My houseplant care had been going so well that I didn't even realize the gnats were a pest- I thought they were fruit flies. I've been trying some methods I found online such as spraying soil periodically with a diluted soap/alcohol mixture, letting the soil dry out, placing rocks/stones on top of the dirt to prevent them from coming out, etc. Unfortunately none of this working. I also have started bottomwatering my plants, but that still has done next to nothing.

For some additional information on my situation- I currently live in the midwest. We are experiencing an unusual week of warmth but after this week it will return to normal November cold temperatures. I have cut back on watering my plants due to the cold (and with many of my plants entering dormancy). To combat the gnats I have been letting them dry out and watering them at that point (about once per week). My plants are all located in areas near a window where they can receive ample sunlight when it is out. When it is cloudy or overcast I have grow light setups to provide them with light. None are located near drafts or overheated locations. I have a wide range of plants - pothos, bonsai, caladium, tradescantia, succulents, etc. (not sure if this information will help but I'm adding it anyways)! The succulents have not been bothered by the gnats, most likely because their soil stays fairly dry and drains easily.

Do any houseplant pros/veterans have any more long term solutions to this? None of my plants have died yet as a result, but I am starting to think that two of my plants have it worse than the others. I am getting tired of removing the adult gnats every single day and have them in almost every room of my home - even those that don't have plants. I don't want to get rid of my plants either, as aside from the gnats, they're doing incredibly well.

Please help me out! I'm at my wit's end!

Hi plantol,

Fungus Gnats are usually present when the soil is retaining too much moisture and depending on the type of soil being used, watering once a week may be excessive. I always advise to pour water atop the soil until it begins exiting the drainage holes, empty any excess water from the tray and don't water again until the top two or so inches of soil feels dry when you stick a finger down into it.

Some plants may need to dry longer than others. Pothos (Epipremnum aureum) for one is fairly drought tolerant and once a week watering to me sounds like too much. I don't grow Caladiums (Caladium) as house plants, they are landscape plants here in the south and it's normal for them to go dormant. If you continue to water, it will likely rot the bulbs.

How are your plants potted? Pot size should be kept to the smallest size possible, just large enough for the root mass and soil; pots too large will cause issues with proper watering. Although many add pebbles to the bottom of the pot, that habit is detrimental to the health of plants; adding pebbles, pieces of crock, etc. does nothing but deter proper drainage. I'm not sure what you mean by bottom watering your plants but having water so close to the roots, especially if they are already waterlogged, will cause rot. I'm thinking you might need to allow a longer drying time between watering.

I used gnat sticky traps that I got from Amazon when I had a bad infestation. They worked GREAT!

It took care of the immediate problem of infuriating bugs flying around and gave me a chance to get a handle on my watering and soil issues. No problems now!

Good luck!

Fungus gnats are a pain.

There are several things you can do or do all.

Get sticky traps.

Get a plant saucer that has some depth and fill it with some cheap beer or wine cover the top with Saran wrap/plastic wrap and make holes in it, the flies will be attracted to it and fly in and drown.

Get some mosquito repellent.

Get some worm castings and mix that into the soil.

Collect some Rove beetles or centipedes, they love hunting fungus gnat larvae.

I've used azamax with great success. It is a pesticide based on neem oil (non-toxic), but the active ingredient is concentrated and it doesn't smell. Two applications and hardly any more gnats.

I use sticky traps as well as this: if you have a small half pint jar mix about a tablespoon dawn dish soap with a tablespoon apple cider vinegar - stir until mixed and place the jar amongst my planters. The bugs like the stink and fly in and drown.

Hi Plantol,

I too have experienced fungus gnat hell and offer my deepest sympathies.

For what it is worth, I tried what felt like every trick in the book before finally finding success with a combination of yellow stickies for the adults and Mosquito Bits (https://www.amazon.com/dp/B0001AUF8G/) for the larvae. I sprinkle a few granules of MB into my watering can and let them sit overnight before watering the next day.

This is also complete overkill, but at some point I got tired of the yellow stickies -- I have to admit I've made a lot of mistakes over the years that lead to gnat resurgences... -- and upgraded to a Katchy for the adults (https://www.amazon.com/dp/B07B6RZP4H/). I've found it to be very effective and unobtrusive.

Good luck with the gnats!

One of the many things you can do as a homeowner to keep your house free of those pests is to learn how to get rid of gnats with Dawn dish soap. Simply combine it with other things like vinegar, stale wine, or sugar and apple cider vinegar.

@cyrusjuliet please don't put those things on your plants. A product with BTi added to your watering can should rid soil of fungus gnats. Look up "Mosquito Dunks" and "Mosquito Bits." No chemicals or risk of damage to plants are needed.

BTi and Mosquito dunks can be impossible to find in some countries. Here in the UK its very hard to get hold of and very expensive. It can be cheaper when bought online from the United States but postage can be high and then there are customs and handling fees due to the nature of the product.

There are other alternatives, various mosquito repellents can work, Hydrogen peroxide is another good one. Using a bio-active substrate can also be beneficial.

I wonder if Miracle Gro offers anything helpful to deter them?

Any other products available in your area with BTi?

Since I quit using peat (potting soil,) I quit having gnat issues.

For me nematodes are the best solution . Easy to use and reliable effectiveness .
I'm using Plantura , but they are also available on amazon

https://biologicco.com/blog/ge...

The nay thing that has worked well and quickly for me is hydrogen peroxide diluted in water. You will find different dilution measures. I use 1/4 cup in a gallon watering can. This also kills fungus in the soil and is beneficial to roots a newly rooted cuttings.

purpleinopp said:
Since I quit using peat (potting soil,) I quit having gnat issues.

Do you mean peat-based potting soil, or that you consider all potting soil peat?
:)

Most potting soil is predominantly peat. Every kind I've ever bought, but there may be some that aren't, so I'll only go as strong as "most."

Peat moss = the #1 thing I try to avoid putting in a pot, for any plant. It may work for some, but I can't keep plants alive that way and don't like to spend time rehydrating it when it dries. I don't like the gnats that are always in it, and the way it compacts into a hard solid thing that won't come off of roots. I don't see anything comparable to a plant growing in the ground, which is what is necessary to approximate as closely as possible for a plant to do well.

Peat moss is a specific thing, removed from bogs where it took a long time to form and isn't being replaced as fast as it is being harvested. Selling it for potting soil is not a responsible thing to do.

Cococoir is a much better and sustainable option. A worthwhile thing to do with millions of coconut shells after the insides have been used.

I have had great success with the product below. It completely eradicated my fungus gnat infestation and also works on spider mites and scale:
Bonide Systemic House Plant Insect Control Granules 8 oz., 0.22% Imidacloprid Insecticide.

purpleinopp said: Most potting soil is predominantly peat. Every kind I've ever bought, but there may be some that aren't, so I'll only go as strong as "most."

Peat moss = the #1 thing I try to avoid putting in a pot, for any plant. It may work for some, but I can't keep plants alive that way and don't like to spend time rehydrating it when it dries. I don't like the gnats that are always in it, and the way it compacts into a hard solid thing that won't come off of roots. I don't see anything comparable to a plant growing in the ground, which is what is necessary to approximate as closely as possible for a plant to do well.

Peat moss is a specific thing, removed from bogs where it took a long time to form and isn't being replaced as fast as it is being harvested. Selling it for potting soil is not a responsible thing to do.

Cococoir is a much better and sustainable option. A worthwhile thing to do with millions of coconut shells after the insides have been used.

Yes, and yes, and yes!

I'm quite fond of this one: https://royalgoldcoco.com/soil...

No peat, which is exactly why I chose it.

I have no experience personally w house gnats or such, but I did know someone say that they can be in your sink/tub drains once they get established in your home, they like the moisture there. Might try treating your drains with some bleach water or similar a few times a week until your problem is gone.

I buy several kinds of potting mix, and I agree coir may be a better choice than peat. But peat does not automatically = gnats. I don't have gnats, haven't for ages.

Also, yes, gnats/flies might be actually living elsewhere than in the plants, and may not be in ALL the plants. Poster is making an assumption that all the plants are the only source.

Rocks on the soil won't help.

We have gnats or drain flies at work- someone's dregs of lemonade from carryout lunch made a nice lure. The lid with the slit for the straw works pretty well letting them in but keeping them confused long enough to drown and die. A few common flies as well.

I have alot of plants.Ive tried & am still trying sticky traps neem oil, hydrogen peroxide, dawn dish soap, tea tree oil and mosquito dunks as well as starving my plants of water because there's no way to bottom water them & I still can't get rid of them!...Burning the house down may be my next option.Before you rush out to get apple cider vinager know that a cup of sugar water with a drop of dawn it works just as well to drown the adults.You don't need plastic over it either, the dawn keeps them in the water.