The best remedy is 'stop drenching the soil'. FGs are more a symptom of a more serious underlying issue (over-watering and/or a poor soil) than they are a threat to the plant.

Others will be along shortly with a variety of suggestions for how you can treat the symptom. Choosing a soil that you can water properly w/o having to worry about it remaining soggy so long it rots roots or impairs root function would not only rid your plants of the gnat annoyance, it would also make it much easier to maintain your plants in a high state of vitality.

Let me know if you'd like to chase that thought a little further.

Al

#1: Follow Al's advice.
Best solution is to solve the problem...

You could use mosquito doughnuts - just a tiny bit in water you water with. As per description on net:
The active ingredient in Mosquito Dunks® is Bacillus thuringiensis
subspecies israelensis. (B.t.i.). B.t.i. is a bacterium that is
deadly to mosquito larvae but harmless to other living things.
(I believe it could be found in granular form).

Soil is long term solution because it requires research and then finding the proper ingredients. Which, I have found to be a huge hurdle. And then there is the whole issue of whether or not you should repot a plant at this time of year. I guess it depends...

I never used it myself, but what are those yellow sticky paper things... You put them in the plant and the gnats are attracted to the yellow colour and then they get stuck. That takes care of adults.

Maybe let the soil dry out more than usual to kill the eggs. Most plants will handle that unless it is a peace lily or something else that needs to be kept moist.

As far as plant pests go, gnats are the best ones to have to deal with. It might take a couple weeks but you can get rid of them.

#1 I have used the mosquito dunk method Rina mentioned and it does work though it is not an instant fix. It will take several weeks as it will not harm the adults, but rather kills the larvae. Haven't used this in a long long time though. I currently have a solution I find much more morbidly amusing. (See #3)

#2 Al's comment regarding underlying soil issues is spot on for most plants.

#3 This is my favorite solution personally ... carnivorous plants. heh Amongst my plethora of flora, I have Drosera (sundews) and Pinguicula (butterworts). They've pretty much wiped out my fungus gnat population. Now I only see the occasional gnat -- usually stuck to one of my dros or pings.

what they all said ...

number one cause.. overwatering ... not letting the media dry ... so let your plants dry out more ...

then one reason it doesnt dry well enough.. old used up media.. as al mentions ...

it wont matter if you solve your issue... if you continue to overwater the plants ...

ken

Fungus gnats are not a plant pest, they are a soil pest. Anytime there is rotting organic matter, gnats will be attracted to it.

Mosquito dunks work.

Pasted info from last FG discussion...
"The active ingredient in those dunks is Bacillus thuringiensis israelensis. It does come as a liquid, Gnatrol and I think that I've seen easy to apply granules. It's safe for use on edibles.

The idea is to use your Bti in your regular watering routine. The last thing you want to do is add more water than what your plant needs. The larvae will ingest the Bti, get sick and die."
- Rhizo

People put these in bird baths to keep mosquito larvae from breeding in them. (Hence the name.)

Letting the soil dry as a plan of control can yield disappointing results... especially if there are multiple plants drying at various times. Also, the soil at the bottom near the drain holes is usually the last to dry, and gnats are usually able to access the drain hole and deposit eggs/larvae there. If drying is taken too far, plants can be damaged, appearance compromised, defeating the purpose of having them. Most house plants don't appreciate drying to the degree necessary to stop the cycle of a FG invasion.

Quoting RioSeven...
"Soil is long term solution because it requires research and then finding the proper ingredients. Which, I have found to be a huge hurdle."

Glad you brought this up! There's no reason to breed FG's just because soil mix recipes may be intimidating, or mention things you find mysterious. Soil mix for a pot isn't a recipe that needs to be followed exactly, though there are some good ones that people share - because they like them and the results they yield very much, for plant growth, and other factors like not harboring FG's.

The texture/particle size is much more important than the ingredients. For those who can't or don't want to mix something up, instead of using stuff called potting soil, cactus soil might be more helpful to folks who battle FG's (and/or have issues with "overwatering" plants.) There is no guarantee what will be in such a bag without discussing brands by name, but the few I've seen do not have a preponderance of tiny particles of peat (and sometimes none.)

In addition to being extremely less likely to harbor FG's, mixes that are more chunky/porous/airy are also more conducive to healthy plant roots - a win/win! Roots need oxygen and moisture at the same time to function, so the presence of more air within tiny spaces in a pot helps roots grow better.

Should one find that potting soil is the only option, adding a significant % of perlite to that can help keep it more airy. Appreciated by roots, more difficult for FG's.

If you have specific questions about a soil recipe, please start a discussion to ask if a search of these forums doesn't yield an answer that satisfies.

Purple, I did not say this person should not try to change to a better soil. I don't find making my own soil "intimidating" or "mysterious." However, it is something that you cannot change overnight.

What I am saying is that some of the ingredients in Al's receipes (for example) are NOT available AT ALL. So to be clear, no matter what I do, I cannot purchase pine bark fines. Not on the Internet, not in any stores. Nowhere. Yes, I can find replacements but they come with their own problems, like the repti bark I bought had soil mites.

So, maybe the OP was asked by her boss to get rid of the gnats. Maybe this person actually has a life and doesn't have the time to run their city looking for soil ingredients for plants they may or may not care about.

This website is great because there are a lot of people of know a lot about gardening, but I find some of you don't remember what it was like to be a beginner. Or you don't consider the fact that some people don't want to make their own soil.

Also, I should point out that telling every single person who comes to this website to make their own soil might turn some people off. It is kinda like someone who knows nothing about cooking learning to make sushi. You kinda have to build up to that point. Learn a bit, read some stuff, experience some set-backs...if you don't know anything about plants you will not make your own soil. It is just to time consuming and expensive.

You don't have to make your own soil mix, although it's not nearly as hard or as time consuming as some folks like to make out. And if you have trouble finding the ingredients of Al's mixes, take a look through the archives of the Container Gardening forum for some great threads telling you how to source these materials or similar products just about anywhere. And you do not have to be religious in following those recipes precisely.....if you read the long-running thread on container soils and the qualities they should have for best plant health, you will be educated enough to make some very acceptable substitutions.

But even repotting plants infested with fungus gnats in your basic, everyday, brand x potting soil will help control the problem. That and not watering as frequently or allowing the soil to remain consistently wet will keep the gnats away.

Making your own soil can be time consuming. Finding appropriate replacements for the ingredients can be time consuming. Sure it is worth it for me, and others, I am just saying that not everyone who owns a houseplant wants to do this.

Weeding a garden is time consuming, and you can choose not to do it, but there are limitations that come along with not making the effort to pull the weeds ..... training your dog, bringing your kids up right, maintaining your house in good repair - all time consuming with tangible rewards we weigh against the effort we need to expend to make things happen

I think there is little question that you can make your own soils for a fraction of the cost of commercially prepared media, or that maintaining your plants in a state of vitality considerably better than beginning gardeners are able to achieve when using soils that are excessively water retentive is a considerable plus. To my way of thinking, withholding the suggestion that making your own soil can not only save money, it can also save you from frustration, enhance your proficiency, and increase the return in terms of satisfaction one is able to extract from the growing experience, isn't in the best interest of anyone other than those tired of hearing the message. The downside is obvious and self evident - you need to make an effort to find ingredients, drag them home, and do what's required to turn them into a quality medium.

Knowledge primes the pump for anyone here to learn, and people need information to make informed decisions. Personally, I could care less what one person chooses to grow in, but I do care that person has what he/she needs in the way of reliable information to help them make a decision re whether or not making their own soil meshes with how much time/energy is available to devote to growing plants. If a person has the time to do research on GW, there is probably enough time to chase after the idea that better soils make growing a LOT easier, and can significantly reduce the number of frustrations that require regular remedial action - to wit, fungus gnats.

I remember my failures as a beginning container gardener - painfully. While studying in an effort to put the failures behind me, I discovered that my soil choices had more impact on my growing experience than anything else I was doing. My connections to the gardening community have always supported that the most improvement one can expect from any single revelation occurs when a grower gains an understanding of how water behaves in soils, and how water retention impacts the growing experience. It's REMEMBERING what it's like to be a beginner that prompts most of us to offer insight into how to improve one's growing lot by improving the lot of the root systems of the grower's plants.

In the end, it's difficult to disagree with the thought that it's better to understand the upside potential of soils that allow you to water correctly with impunity than to remain uninformed, no matter how convenient a bagged soil might be. Also, discussions with growers who clearly aren't going down the make your own soil path often lead to discussions about how to deal with the excess water retention we'd all be better for avoiding.

Al

This post was edited by tapla on Tue, Oct 28, 14 at 21:23

I do agree that making your own soil is cheaper but only in the long run.

So, if you don't know anything about houseplants it is obviously cheaper to buy a $6 bag of MG then to spend $50 on ingredients because you don't know if you will ever use it all. But certainly, for someone who knows they will be using all the medium they make, it is cheaper.

I think what would be wonderful is if there was a commercially available potting mix that did not kill your plants. When you are just learning to grow plants it is very strange to find out that the stuff you buy to put your plant in will eventually kill your plant. I mean, it sounds crazy!

On the other hand, I guess there are tons of examples of this. For example, you know what will make all your glass streaky? Windex! But they claim a streak free shine. I think it is called advertising your weakness, and MG has certainly done that.

I agree that initial outlay can be higher if you're looking for the lowest price per unit, but all of these pieces of knowledge are what's needed to make self-interested decisions. There's no such thing as too much information, as long as it's not BAD information.

Personally, I look for people who are enthusiastic and eager to explore. It's pretty easy for experienced growers to figure out who is going to benefit from some tutoring and who has already tuned out, which is one of the big reasons no one ever gets "told they should" make their own soils. If extolling the potential benefits of a well-made medium isn't enough to pique interest, the would-be coach might as well save his breath for the next in line with botherations to unravel.

Al

RioS., I'm left wondering if you read what I wrote? I'm flummoxed.

I definitely didn't say anyone should make their own soil, and wanted to encourage you in particular, and provide some info to investigate options since you'd broached a sidebar to Hpny's discussion. I provided several paragraphs about other options, and what the goal of the recipes is, so folks can use that part of the info to understand how they might improve what they are doing without "run"ing> their city looking for soil ingredients for plants they may or may not care about."

Repotting *does* change things overnight. Even, as GG said, a fresh batch of the same old stuff you used before.

"What I am saying is that some of the ingredients in Al's receipes (for example) are NOT available AT ALL.
I was agreeing with you! I only buy plant stuff in person and live in a rural area.

"I cannot purchase pine bark fines. ...the repti bark I bought had soil mites."
I've never owned either of these ingredients.

"Or you don't consider the fact that some people don't want to make their own soil."
I'm quite sure most people don't, and wouldn't say they are wrong if they don't. I gave several other options that are commonly employed to avoid doing this.

"telling every single person who comes to this website to make their own soil might turn some people off."
Nobody is doing that, certainly not *me!* I've never done that, don't intend to start, and don't see how one could get that from what I said, which was the exact opposite of this.

"I don't find making my own soil "intimidating" or "mysterious."
That's great! Many people do. These are common feelings, that I share. No offense was intended, a description I would ascribe to myself. (Intimidating = $. Mysterious = I've never followed one of these recipes, only used a final product given to me.)

"...don't remember what it was like to be a beginner."
If I ever stop feeling like this, I would get bored. Sure, I've had plants around for a long time, a few of the same ones for a few decades. I conduct unorthodox experiments, make observations, make reasonable predictions about their future, but I don't ever delude myself that I really know anything, or more or less than anyone else. People used to know the world was flat. I'm a skeptic to the core, especially about what I think I know. Everything is open to further investigation and discussion.

I'm sorry my attempt to provide some info was objectionable to you, but don't mind sending info out into the cosmos for whoever might find it relevant. Best of luck and happy growing!

We have a lot of plants here in the office, so repotting/replanting would be a hassle, as well as the fact that we are here to work, not garden! So I was thinking more in the lines of a soil drench that would kill off the bugs/larvae/eggs and whatever is in there. The boss says, if we can't get rid of the bugs, all the plants have to go. So, first I will try the sticky things, mosquito things and possibly the peroxide drench and see if any of them work. Thanks for all the suggestions! I'll let you know if it works.

Fungus gnats are so annoying! we had cockroaches and when I brought sticky traps for them, I also used some on the gnats, and in o time at all, they were almost eliminated. They are still there, but almost unnoticeable....I usually take regular soil mixes and add more perlite as a compromise for buying all the materials to make my own.

I'll bet that the boss will object to the sticky traps! I would, if I were in charge. That would be a very unprofessional look for a business setting.

Fungus gnats can be a true plant pest in containers, where they are very happy to nibble on tender roots tips. Outside in the soil, they rarely cause problems for plants.

But the mosquito dunks, or Gnatrol should do the trick, as long as you follow the directions, and apply it ONLY as an addition to the water on watering day. No extra drenches allowed. Unfortunately, it might take several weeks before you stop seeing gnats.

Other simple methods that can be helpful include adding a layer of horticultural grade (or food grade) Diatomaceous Earth, not pool grade; add a thick layer of coarse sand; allow the plants to dry out considerably in between waterings; don't allow multiple care givers.

I have also been battling these horrible and persistent things for months! I'm not sure where they came from -- perhaps through the window screen when a window was open -- but they quickly infested all my plants. I used to have about 25 plants; now I'm down to 4.

I read the forums and tried almost all of what's been suggested, with varying effectiveness. I used to only water once-a-week, but I totally stopped watering my plants to the point where they were bone-dry. But as others have said, fungus gnats don't die from that and can wait for more moisture again.

Traps of paper, vinegar, tape, etc. did not seem very effective on the gnat population.

I've used pyrethrin sprays, mosquito dunk stuff in the water trays, even seriously-potent insecticides on my plants. The numbers decreased a bit, but they were not eradicated. Fungus gnats can and DO infest more than just the top of the soil. One of the main places I noticed them was coming from the drain holes under the pots!

I've replaced the top inch of soil with sterilized sand. The fg can still be seen crawling (or dead) on the sand, plant pots, shelf, or even hiding in the very base of the leaves of spider plants. (They are very very resourceful bugs!)

The last option that I am trying next is to thoroughly hot-water wash my plants (removing all soil from the roots) and re-pot them in new and sterilized coarse soil. If that doesn't cure it, I'm going to be forced to toss out all my plants. I'm hoping I don't have to do that...

I had fungas gnats once, a number of years ago. I got rid of them by watering all of my pants at once with hot, hot tap water. Not boiling, of course!

Spider-gram, I doubt there's any need to wash all of the soil from your plants, but you can.

I just watered mine, and the gnats were killed instantly. It worked like a charm.

Jasdip, thanks for your feedback.

I have never ever had such a sudden infestation of gnats in all my years. It has been quite an ordeal! Some of my spiders were over 15 years old, and were still lush and awesome. It's been sad watching them fail in spite of all my efforts...

The plants were washed in a tub of super-hot tap water before being repotted in new soil yesterday. I used a better-draining soil with additional BTi granules mixed in.
I then topped the pots with something from the plant store called GnatNix.

Down to two plants now, I have my fingers crossed for their survival. The remaining plants seem to have endured the hot water better than anticipated and look ok this morning but It's too early yet to tell if the gnats are truly gone. Will let folks know if this worked.

I hope others' plants are faring well!