Fungus Gnats in my houseplants...

Noel, MO(Zone 6a)

I would like some organic methods of getting rid of Fungus gnats in my house plants. They are taking over. They are little tiny flies that lay their larvae in the soil. They live in the soil till they become flies themselves and start it all over again. But the problem is, is that I can't get rid of them (yet). I've had them for a couple of years now. And I think they only live off of the organic matter, I don't think they actually hurt the roots of the plants. But they are annoying. And I don't Like them.

The problem is, is that we have a housecat who likes to taste plants (especially any considered poisonous) and well I don't want to use a harsh chemical because it could hurt the kitty. Plus I can't afford much at this time either.

So what do you think??


Huntington Beach, CA

Someone who works in a nursery told me to use some liquid dish soap in a spray bottle and to spray the plants with that. I have tried and what I found was that the little gnats sort of stuck to the ground after having been sprayed and the ones I can see I just remove. The soapy solution does not seem to hurt the plants or the leaves, although I find that more gnats soon seem to come and replace the other ones. Once in a while I put my plants in the shower and gently spray them with luke warm water. That helps also, but is of course quite a bit of work, without talking about the dirt......

Westbrook, ME(Zone 5a)

I've had trouble with my seedlings and fungal gnats this year. The little wormy larvae are what cause the problems. The adult flies are just a nuisance. They probably don't do a lot of damage to large house plants but they can really mess up a batch of seedlings. I tried several home remedies recommended like the soapy water drench, vinegar traps & diatomatous earth. None of them really seemed to put an end to the problem. I finally ordered a BT product from Golden Harvest Organics and they seem to be disappearing. Here's the link - I don't think the Bt would harm your cats.... you don't spray it on the leaves you drench the soil with it.

If you only have a few house plants you may just want to re-pot them with fresh soil - and throw the old soil out - maybe that would take care of them. I think I got infested when I brought in a few plants in from outside in the fall. I ended up getting rid of the plants when I saw they had a zillion nasty little larvae worms in the soil.

I agree with poppysue's repotting idea. I had a gnat problem with a plant once. I took the plant outside, dumped the soil in the trash bin, and then actually removed the soil from the roots of the plant! I did this with a 5 gallon bucket full of clean water. I emersed the plant in the water and shook all the soil off.

Then potted up in new (clean) potting soil. The problem went away.


Noel, MO(Zone 6a)

Didn't help!

I did that a couple of times. But I now have way too many to do that plus it just didn't work. Probably because the adult gnats were still in the house, and they just laid more larvae! I can't spray stuff on my African Violets. I might could on some of my other plants, but it would hurt the AV's leaves.

Do you really think I need to go for a chemical? If so I'd better hurry, because my brother's 9 almost 10 month son could be moving in with us (my brother is going through a divorce and custody battle). So we are trying to baby proof the house, and get rid of chemicals...

I've heard of some success by some people with a product called Neem, any of you all try it??


Westbrook, ME(Zone 5a)

I think with neem oil you would have to use it as a foliar spray. The BT is mixed with the water when you water your plants. The neem may be more effective on the adults. Have you tried the yellow sticky traps? What I did was drench the big plants with the bt and I use a dilute solution of it when I water my seedlings. I also have a couple of yellow sticky traps to catch the adults. Bt & neem are both organic pesticides and aren't harmful to humans or animals so I don't think you need to worry about them being poisonous. That same site has the neem oil too.

Oh ya! I should also mention that I chased the adults around with a can of hairspray too. They drop like flies!

Are these bugs your speaking of look something like fruit flies and are they slow and easy to "squash"? I have some seeds growing in the kitchen and bought some clearence plants and I have seen these things flying around the kitchen every now and then.

(Zone 6a)

I don't know if this will work, but I dug out one of my g'ma's old gardening/plant books. For many types of pests, they put the whole pot, dirt and all, into a large tub of lukewarm water and left it there for a couple of hours to "drown the pests". They even submersed the whole plant at times! Don't know if it will work, but I don't think it would hurt anything. Of course, if it's still too cold outside it could sure make a mess in the bathroom or kitchen! :)

Becky G.

Milo, IA(Zone 5a)

The problem with these bugs, is that every 10 days or so new larvae hatch out in the soil. One solution is to mix 1 teas. of liquid dish soap with a quart of water, and water the plant with it. You can also spray the leaves and plant with the solution. You might have to do this at 10 day intervals for awhile.

Lakota, ND(Zone 3a)

Another thing to try is a yellow index card painted with honey and then lay it on top of the soil to attract the gnats and then they stick to the honey. You can also buy the stuff to spread on the cards, it is called Tangle-Trap. Jung Seed has it ofr $5.95 for an 8 oz. can.

Be sure and use the bt and neem in a well ventilated area. They both have a strong smell.


Weyburn, SK

One lesson I learned was that fungus gnats are usually a sign of overwatering the plants. Letting them dry out more will usually cure the problem. As for spray I use rubbing alcohol for any pests on my plants, including white flies and aphids. With over 150 plants there is usually at least one with an insect problem.

Hughesville, MO(Zone 5a)

Ehowell is right. Fungus knats are attracted to the moisture in the soil. Let the soil dry more between waterings. I know you said you have cats who like to nibble on your plants, but if you use the systemic insecticide from FertiLome in your soil I don't think that will be a problem anymore. No, the cats won't be dead, they just won't like the smell. Try raising some grasses indoors for your cats to eat. They will like them better than the other plants and be healthier too.

Scarboorough, ON

Thanks for all the info someone emailed about this problem and I passed it on to her and her mum. Dave's Garden does it again. :)

Scarboorough, ON

oh dear I was 13 so had to make it 14....silly but. As Mcloud used to say Well there you go.

Price, UT

thats usally how i control the gnats is with watering thats what causes it letting the plants dry out wont harm the plant and usally cure the prob try putting your plant on a watering schedule that might help

Petaluma, CA

I'm amazed, AMAZED that since I got a little Sundew, a carnivorous plant with sticky leaves, and put it next to a group of gnat-infested plants, they have all but disappeared. I haven't seen a fungus gnat in weeks. So something does eat them.
However, the occasional scale and (gasp!) mealy bug are still eluding it!

you can also try coarse, builders sand. lay about an inch or so of sand on the top of the soil--the larvae shred on the sand as they crawl up to become gnats and if you kill them before they start, you'll lick the problem. the sand doesn't hurt cats or plants and will eventually mix into the soil.

ummmm, i'm not sure jewel. probably could get it at home depot/lowes--my sand came from my front yard leftovers when the builders were gone had thought about growing cactus in it, but the pets and kids keep that from taking. i just go out and get a pan full, put it in the oven at 200* for a couple of hours to kill the germs/bugs and then use it the next day. check with your home improvement stores, i would bet you can get it there. good luck


Sykesville, MD(Zone 7b)

Wow... what great ideas!! I guess I'll have to also look for a posting on scale.... ewww ! =)

Well, the "drier method" worked last year, but seems that a bag of potting soil stayed moist for months and started their own little colony. My new MothersDay Rose is totally swimming with the hateful little buggers!!!! I have sent off to Gardens Alive for a drench to treat all the little kiddies, and will report back.

If the library 'charged' for dead FG's I would STILL be paying the fine! Seems that borrowed, used library books smell much like lovely, live earth! Must've smashed hundreds last year! Most every plant I have recently potted has the dreaded FG's, and every retail outlet in town has been plagued also. What a horrid, nasty little pest! Could put you off coffee for life (after seeing so many do the backstroke!)


North Wales, PA(Zone 6a)

Specialty nurseries may carry the coarse builder's grit/sand. My Home Depot and Lowes only carry fine sand--you do not want this as it will not do the trick on the pests and it will compact the soil, keeping moisture in too long. I have found one nursery that sells it--three different grades. I use the coarsest for a top covering on my sansevierias. I mix the other grades into succulent potting mix for better drainage. Check with your favorite nursery and if they do not have it, maybe they can recommend another resource for it.

I very much agree with the advice about letting the plant dry out a little more prior to watering. If you go with the sand/grit method, also put some in the saucer.

Good luck!

New York, NY(Zone 6a)

Another safe technique is to place inch slices of raw potato on the surface of the soil. After a week discard the slices along with the larvae inside. Repeat this until there are no more larvae on the potato slices.
Will Creed

I have used the sand technique, and it helped but be careful not to get it on furniture, and glass: it scratches!! I love all of WillCreeds advice, and am chopping potatoes as soon as I get my lazy self off this computer.

Santa Cruz, CA(Zone 9a)

I just read recently that sprinkling snuff on the surface of the soil and watering as usual will kill these buggers. Snuff is essentially tobacco, so it shouldn't be used on vegetables (because of TMV controversy). ALso, watering with weak tabacco tea is supposed to work as well. Now, where does one buy snuff these days?

Tucson, AZ(Zone 9a)

Hi all!

I too have had a fungus gnat invasion in the last year. What I found best was to drench all soil and leaves (outdoors of course) as soon as I see a gnat, in insecticidal soap and then let them completely dry out (1-2 weeks). I let them dry to the point where the plant will look ready or stressed for water. Then I only water from the bottom if possible. If I can't, I use more insecticidal soap in the water everytime I water. From my research, I think they are pretty harmless, unless the soil is not to organically rich, then the larve prey on the plant roots. They are pretty annoying and embarrassing if you have company and a gnat decides to commit suicide in your guests food. :)

The BT drench or spray is not harmful to foliage, pets or people ( or, so I've read, anyway--I hate to make claims). It is a natural parasite of the fly larvae, Bacillis thuringiensis. Different strains are used in different products for different larvae. "Gnatrol" is the strain for gnats. It is sold under different brand names, like "Knock Out Gnats", sold by the mail order company, Gardens Alive. "Dipel" is the strain used for bud worms, like the kind that ravage geraniums and petunias. Again, Dipel is sold under different brandnames. Safers has a product. I recently read somewhere that BT is used by organic gardeners. Can anyone confirm that??

I have had a problem with bud worms on my outdoor plants, and have sprayed twice with the Safer's product. It works but I have had reoccurance, and, drat, I need to spray again.

I had a problem with these little worms and flies living in my pot soil. I declared war on those little buggers. I tried replacing the soil but they came back. I tried destroying them with insecticide but that failed too. I covered the soil with alummunim foil to cut them off. It slowed them down but they found ways to escape. I decided to Napalm the suckers. I got some boiling hot water and dumped it right on top of them(Suggest taking the plant out first). One blow wiped their entire Army. It was like a NUKE bomb. Yeah Victory is mine!

Kylertown, PA(Zone 5b)

I take a yellow plastic container, such as one for dish or laundry soap, cut a strip about 5 x 10 inches, and punch a hole in the top for hanging.

Then I slather the whole thing with Vaseline and hang near my plants.

Fungus gnats and other bugs are attracted to yellow, and I usually catch quite a few this way. It doesn't solve the problem entirely, but it helps.

And you don't have to worry about harsh chemicals or your kids or pets getting into anything toxic.

Sykesville, MD(Zone 7b)

I vacuum them up with the vacuum hose. The suction gets them quickly (which is great because they are quick )and finds them where ever they are hiding. I skim it across close to the soil and close to leaves. There's no escape. ONCE a day for about a week and you should have it solved.It's super easy, no mess and nothing ugly to detract from pretty plant.This has worked like a charm for me for a long time. No parents = no babies . Good luck! =)

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