My own experience is that once you have the gnats, nothing gets rid of them other than BTi - Bacillus thuringiensis subspecies israelensis, the same BTi used for mosquito larvae control (safe for pets, people, fish, birds). More careful watering habits may prevent getting them again, but it's hard to let the soil dry out enough (all the way to the pot bottom, I've seen the gnats go in and out of the drainage holes) to kill the larvae in the soil, stop the breeding cycle, without damaging plants. Others have suggested a layer of sand on top potting soil, cinnamon etc...I needed the BTi to rid my plants of the gnats after bringing home a herd of them in a new plant - they infested every pot in every room of my house.

There are water soluble commercial preparations made that are easy to use, Knock Out Gnats, Gnatrol etc, or - mosquito dunks may be easier for you to find and you can make your own solution by floating a mosquito dunk in a container of water overnight, then using that water to water your plants...for a minimum of three consecutive waterings on your regular schedule or as your plants need water. Then give the balance of the package of dunks to a friend with a water feature in their garden :)

If your potted plants do have these "fungus gnats" you will see a lot of the adults flying around the plant as well as the larva wiggling in the soil. The larva need a fairly moist envirnment to grow in so checking the soil carefully before watering is always necessary and keeping the plant a bit dryer than you think it can stand will help a lot. Yellow sticky traps can help trap the adult flies so they do not mate and lay more eggs that will become more larva that wil become more adults, because the only reason the adults are there is to lay eggs.
The BTi suggested above might be necessary of just letting the potting soil get dryer does not, but using Neem Oil products would be more like using a bazooka to kill a mouse.

#3 still leaves you with one food source for the gnat larvae - the main reason we become concerned over infestations of the gnats (not that swatting adults is anyones idea of entertainment :))

"The adult stage is primarily a nuisance, whereas the larval stage is directly responsible for plant injury by feeding on plant roots or tunneling into stems. In addition, larva can vector soil-borne pathogens directly through feeding or creating wounds that allow entry for soil-borne pathogens."

Yes I do think that adding organic matter might not be helpful at all in my case, I guess I was hoping the cinnamon would kill of fungus in soil.

I guess I'll have to head of to a gardening centre to get some sand then -- I was at a beach today but wasn't sure if the sand there was clean enough or not for gradening purpose lol! And also see if I can find the BTi thing.

One thing is find curious though -- I still don't see any larvae like things on the soil.

And the red wine doesn't seem to be attracting the adults either -- maybe it's too cheap a wine. lol.

You are confused, me thinks. They are not called fungus gnats because they feed on fungus. The larvae are found in organic-y (like your potting soil) soil or potting mixes and feed on that kind of debris. When in large numbers and confined to a container, they will also feed on tender plant roots.

Fungus gnats are not like fruit flies in that the adults will never be attracted to juice, vinegar, or wine. Fruit flies can be trapped by such liquids because they lay their eggs in over-ripe fruit. Fungus gnat adults deposit their eggs in that moist, organic-y environment of the potting medium.

Best not to use beach sand for your containers. Sharp builder's sand is a good product for this purpose. But, if you have a really bad infestation, don't hesitate to locate some of those mosquito dunks. They should be readily available at this time of year.

Thanks Rhizo_1 !! I also think that i'm probably really confused too! I'm very new to gardening and being easily intimidated by bugs doesn't help much I guess!

I don't think it's a really bad infestation for now: usually I find less than 10 resting/ flying around my 10 or so pots, most of the time 5-6.

So I'll go discard the wine and maybe look for some sand if needed. Can I use those packs of sand sold at gardening centers?

Is it horticultural grade (coarse) sand? I haven't looked for small bags, the last time I bought sand (builders grit) it came in an 80# 'tube' - probably not something an apartment dweller would want. Horticultural grade sand is similar to parakeet grit...most grocery stores would have parakeet grit in small boxes in their pet supplies section.

Just remember, sand on top doesn't deter the gnats from flitting in and out of the drainage holes to lay eggs.

I don't really know what kind of sand they are as I merely walked pass them.

What is the ultimate way to eradicate gnats if even sand are not useful?

BTi - Bacillus thuringiensis subspecies israelensis

Found in liquid form Gnatrol, Knock Out Gnats, probably others, and water feature/garden supplies for mosquito larvae control, i.e. mosquito dunks etc

Sand and BTi, here I come!!

Well, maybe after I deal with the new comer-- Aphids!!

ahhhh...... I just realized that gardening is a life long battle.

Oh my-- I have been to two gardening stores and none have any BTi products nor mosquito dunk.

I guess i'll just have to live with them for quite a while! =(

I've seen the mosquito dunks packaged on cardboard 'hangers' so that they can be displayed all over the pest control section of big box stores. I'll attach some pictures for you so that you know what they might look like. Also, they would be readily available on-line.

Here is a link that might be useful: click here

letranger, fungus gnats and fruit flies are often confused but there is one difference which tells them apart easily. The adult fungus gnats are attracted to the human face (apparently it has to do with carbon dioxide and NOT my good looks), whereas the fruit flies tend to cluster around the fruity stuff. I have read that small pieces of raw potato placed on the soil surface will attract the larvae of fungus gnats but I cannot vouch for that. I have potatoes and plants but so far, no larvae. Maybe the potato thing is not not a reliable guide.

I think I should ask this very obvious question after a few days of BTi hunting without any success... is mosquito dunks sold in Canada?????

Or, any reliable online retailers who would ship it to Toronto?