Help with house plants and gnats, anyone? PLEASE HELP ME!!

I started out with a few house plants a couple years ago. In the last year I have alot of out door potted and grounded plants.. So I am still relatively new at this..

During the summer GNATS have taken over my house... I have tried many things that I have read just on the net as to what to do... Even tried Thuricide Concentrate mixed as per the label. I have treated 3 times, drenching the plants.. It appears to calm down for a short time but then I'm attacked by those pesky creatures again. I really do not know what else to do. Quite a few of my "houseplants" have become patio plants and are thriving, but surely still with the gnats. Ugh!!

I have a thought.. but please someone stop me if I am about to become a house plant murderer, as this is very pre-meditated. I am wondering, as it is early fall here in Alabama..if I repot all of my houseplants. New medium is where I want to start. I have read that if I cook the soil in the oven to specs that it will decontaminate the soil. When repotting I normally take some of the native medium with the plant into the new pot.. However this will bring along the culprits and their larvae..

Is it safe to clean all the old soil from the roots and repot completely using new, decontaminated soil? Am I going to kill all my house plants by doing this??

Please someone help me.. I don't want to kill them all but I am truly at my wits end. Not being able to sit down to watch TV with a glass of iced tea without finding a gnat in it two seconds later is killing me.. DRIVING ME CRAZY.. not to mention the darn things flying up your nose is quite annoying..

Good morning Daisy; "dual action rose and flower insect killer" by Bayer. Is a very effective product. Try before you get "drastic" Good luck. :) Daisey

yes baking the soil works to sterilize it. I have waaaaay too many houseplants to even consider doing that....anyway yes you can wash all the old soil completely from the roots it only hurts if you don't repot them right away

I know Bacillus thuringiensis israelensis (the kind of BT used on mosquito larva) works for fungus gnat larva. I don't remember all the details right now, but you can google for more information.

Thank you soooo much... As you can see I have had enough. I can't even sleep. Darn Gnats!!!

I will try the suggestions here and let you know what becomes of the varmints. Thanks again.

Ok, In looking into this more I realized that the Thuricide I have been using is a form of Bacillus thuringiensis israelensis.. As it has not been working for me (maybe my infestation was too large or overwhelming for it) I went drastic. So all weekend, I have cooked soil and repotted plants. Seems to have worked so far..xx fingers crossed xx. I am still killing the adults that are already flying but there seem to be less, by a long shot. I was able to have a few glasses of something to drink without finding bugs in it..

I sure hope that it last.. this has been alot of work. It seems that my plants have survived the drastic measures. I repotted, and watered them, made sure they were drained extremely well. The only one that is drooping is my beautiful Scheffalera. I think it will come around. I bought it almost dead from Lowes... (they don't take good care of their plants) and I was able to revive it and it has been thriving. Surely it will come back from this.. Droopy but seems to be perking up.. Again my fingers are crossed!

Thanks to all !!!

Scheffalera is a hearty plant. My wife has four of the biggest ones you've ever seen. Wait until it dries out pretty good between waterings, then give it a good soaking.

Actually Thuricide is a different subspecies, Bacillus thuringensis kurstaki, and is for killing caterpillars. It will have no effect on gnat larva at all. You have to have the Bacillus thuringensis israelensis to kill those nasty gnat larva. It's confusing. The israelensis is most commonly found in mosquito dunks. You can crumble them into a jug of water, let them soak a day or two, and then water your plants with the innoculated water. The bacteria will then be in your soil and will eat up any larva that hatch in the soil. If it were me, even with the now clean soil, I would water with the BT innoculated water for a few weeks just to prevent the cycle from starting over again. In fact, I need to do it to some of my plants because the gnats are becoming a problem. Aggravating creatures! Good Luck! :)

Jim41, Thanks for the info.. It just made me smile. I don't want to lose that plant. I really like it and since I'm still kinda new at this, I am really proud that I saved it from near death.

Danita,
Thank you as well. Good info and I fully intend to follow your advice.

It worked.. I am gnat free....

I ended up repotting ALL my plants with new medium that I baked to specs, then allowed to cool completely. Its been about 3 weeks of NO GNATS.... Love it.

I will start the mosquito dunks probably this weekend and use them periodically just to protect against re-infestation.

Thanks for all your help.

Be PERSISTANT! It may take a while to get control. I use sticky traps (to get the adults) as well as mosquito dunks.

My hubby picked up the sticky traps at the hardware store.. I was amazed at how many gnats end of up those things. WOW.

Thanks for the insight. Persistence is the key, Got it. : )

i have a question--how do the gnats start? i have a couple plants in my house--one of which is dying or died or something (it has a plant mold as well)--and it seems they all have these pesky gnats flying right around the soil and throughout the house. it's quite annoying. could it be my soil as well? last week i repotted a plant and when i opened the bag of potting mix, a posse of gnats descended on me. i'm going to try the mosquito dunks over the weekend.

this site is such a wealth of priceless information!!

My question is the same one that Marques asks. How do the gnats start?

I have been potting indoor plants for decades, and I have never had gnats indoors until now.

They seem to be in every bag of potting soil I buy. I hate to throw money away, but I don't want to use soil with gnats and gnat larvae, either. Help!

Gnats love fresh potting soil because it's full of raw plant materials that feed the fungus they eat. Most potting soil does not contain gnats or larvae or eggs but a couple of gnats from infested plants will rapidly colonize a freshly repotted plant. It only takes a couple of gnats on a new plant to infest all of the soil in a household.

There is an easy and non-chemical way to get rid of gnats: Sand. They need access to moist potting soil in order to lay their eggs. If you smooth the soil and add enough sand to completely cover the soil (about 1/4 to 1/2 inch) the gnats cannot lay eggs. I usually add some smooth pebbles in one spot so I can pour in water without making a hole in the sand. If watering displaces some of the sand, smooth it back into place after watering. Also, allow the plants to dry more between waterings, this keeps the top of the soil drier so they don't lay eggs and slows the growth of the fungi that the larvae feed on.

Try it, but expect to keep finding gnats for a couple of weeks. The larvae that are in the soil will keep hatching and emerging but they will not be able to lay eggs so they should start to disappear in about three weeks at the latest.

Good question. I believe they swarm out if a porthole from hell. LOL. I adopted my new pests from nurseries and Lowes. I didn't even know what a "fungus gnat" was until this year. A cold winter and first time houseplants. Now I see them in every garden center I go to. I never payed any attention to them until all my newly rooted plants somehow regressed back into rootless cuttings. A fellow member mentioned fungus gnats. And sure enough... that was the problem!! So after tring many different things. What worked the best for me was the "bacillus thuringiensis subspecies israelensis" same ingredient as mosquito dunks. Only this is a drop form. I got it at my local hydro shop. It is called MICROBE-LIFT BMC. it is made by Ecological Laboratories Inc. It costs $15.00 for two ounces. I topped all succulents with sharp sand. All other houseplants I used vermiculite to top soil. I got the sticky window film. I cut it to size, put a yellow "post-it" note on backside. This helped so far. Time will tell. As far as where they come from? (aside from bringing them home with new plants) I am guessing that the uncommonly cold winter we had would be main factor. I for one experienced freeze damage this year pretty bad. The gnats are all about the damaged/rotting remains in our yards, our neighbors yards, etc...

Don't forget the chase the little bugs down with a vacuum. It's really satisfying to catch them, and you will start to feel the effects of this aerobic activity, much like fencing with swords, lol. May the force be with your vacuum.

You guys are too funny, lol. I thought I might try the mosquito dunks if I inquire at a swimming pool supply store. Okay, sand--where and what kind? Any suggestions?

I don't have an infestation at the moment, but I have thrown out otherwise perfectly good, brand-new bags of potting/orchid soil because I can't stand the idea of creating more work for myself.

Thanks,
TJ

Oh, forgot to add that you shouldn't use salt from the beach. The salt in the sand is not good for plants. Plain sand from the concrete aisle of the hardware store works just fine.

You can sterilize soil if the new soil is the problem. Before you use it, bake it at a low heat for an hour or 2, check online for the best method. I put a pan of soil on top of our woodstove before planting some delicate transplants. Hopefully, it would kill eggs, too. I got mosquito dunks at Lowe's, sometimes Walmart has them, and Ebay. And the shopvac gives great fun, chasing the little boogers.

Also, watch out for "whiskies", as my grandma called them. They are actually fruit flies, and they love bananas. I have closed up my house and filled it full of flying insect killer and went somewhere. That worked for fruitflies. The fungus gnat, I knew about in 1973, but thought they were fruitflies. I did not know anything about fungus gnats. But I do now. thanks everyone.

okay, so i got the mosquito dunks--what now? do i sit them in water... do i put them on the plant soil's surface... do i stick them in the dirt... any ideas? thanks!

The bacillus that I have is in a drop form that I add to water. I believe that you let the pill form dissolve in water bucket overnight and then use that water. :)

Read the directions! In a watering can toss one quarter of one in. In a rain barrel toss half of one in. These really work.

Wow...I'm so glad I found this thread!! I'm off to find mosquito dunks and either sand or vermiculite, then will get to work on my plants. I've seen only a couple of gnats so far, but do NOT want to lose anymore plants :( I'm starting with the gnats and then working on figuring out my lighting situation.. too much shade around my windows..one tiny south window that gets full sun.

Wish the "search forums" feature was working.. I need to find a thread dealing with light.. High light, full sun, low light, part sun.. my head is spinning! lol

thanks everybody!

spray them with off bug spray;

I have discovered that if I water my indoor plants from the bottom, however, NOT to the point that the top layer of soil gets wet, it will reduce or eradicate the gnats. If there is a severe infestation, it will take about three weeks to notice a reduction, however, if you perservere you will notice a difference. Snug, :o)

Fungus Gnats:

http://en.wikipedia.org/wiki/Fungus_gnat

http://culturesheet.org/pests:fungus_gnats

I had a problem years ago with those things! I learned that it was because my soil was staying too wet, over watering was my big problem! I think the larvae or eggs were in the potting soil and with the consistently moist soil the eggs kept hatching. I used insecticidal soap for houseplants that got rid of them totally and I haven't had the problem ever again. I let all of my plants get dry between watering and they've adapted well to my conditions.

plantladylin: the reference material you supplied is excellent. Thank you for sharing it!!
Snug