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Fungus Gnats

Posted by eileen_plants z6ny (My Page) on
Tue, Jul 11, 06 at 15:53

I have sixty house plants in one room with a southern exposure. I've noticed some fungus gnats have gotten quite a foothold in the plants, especially those I'm growing from seed. I've been using Ortho insecticide, but it doesn't seem to be doing the job and I don't want to keep spraying and possibly damaging the plants. Any suggestions most appreciated. These appear to be the only pests I have. I think its because I tend to water in the evening after I get home from work, and the water is not evaporating as quickly as it would if I were watering in the morning - is this a legitimate concern? Should I switch?


Follow-Up Postings:

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RE: Fungus Gnats

Eileen, gnats find their way in our soils due to it being constantly moist..if you can allow soil to dry out more and place a fan for air circulation in the room this should help..
I too am growing plants from seed and those plants have gnats, but once I repot them in their own pots, bring them up from the basement where they're growing, the gnats die. Is there a way you can water less? If possible, water in the morning..Toni


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RE: Fungus Gnats

  • Posted by morz8 Z8 Wa coast (My Page) on
    Tue, Jul 11, 06 at 17:05

BTi, (Bacillus thuringiensis subspecies israelensis) worked perfectly for me. Odor free, biological larvicide, safe for people, pets, birds. Kills the larvae in the soil and stops the breeding cycle. If your infestation is heavy, you may need to use it three consecutive times as a soil drench on your regular watering schedule.

You can find it in products specifically made for gnat control like Knock Out Gnats or Gnatrol. In a pinch, you can make your own by buying a package of mosquito dunks as I did (same BTi), floating a dunk in a container of water overnight, then using that water to water your plants. Later, I bought the Knock Out Gnats to have on hand (coupon, Gardens Alive) since I grow so much from seed.

It's the larvae feeding a fine roots (particularly seedlings) that can be damaging, not the adults which are mostly annoying.


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RE: Fungus Gnats

Thank you so much to Toni and morz8 - I will do everything you both suggested, including getting some gnatrol! I can't tell you how helpful it is for newbies to plants like myself to get the kind of advice I have gotten from this website. Thank you again for sharing your experience with the rest of us and for being so quick to help. I appreciate it so much.


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RE: Fungus Gnats

No problem Eileen. Fungus gnats are a pain, but it could be worse, like mealy, scale or mites.
I don't care to use chemicals, except for fertilizer. Even though they say some chemicals are safe around birds, (which I breed) I steer clear. My logic is, if something can kill a bug how can it not harm a bird? But that's just me..I'm super cautious using any type of chemicals, including cleaning products, in the house..I've heard too many horror stories regarding pets and chemicals.
Morz, no offense, but again it's me. Toni


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RE: Fungus Gnats

  • Posted by morz8 Z8 Wa coast (My Page) on
    Wed, Jul 12, 06 at 10:25

Toni, BTi can be used safely in ponds and birdbaths for mosquito larvae with no ill effects...

And no offense taken. I rarely find need to use a chemical (although I do bait regularly for slugs in my gardens), but BTi is found in organic solutions vendors - a natural bacterium.


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RE: Fungus Gnats

You've been given some very good advice, eileen. Please know that there are very few insecticides that are safe to use inside. Safe, in terms of YOU! (That's what I'm worried about, lol.) Hopefully, your Ortho product was manufactured for indoor use. If not, you need to save it for various outdoor situations.

Tony, I am a wee bit surprised that you don't know about Bt. Those of us who will not or cannot use chemicals (the HARD stuff, lol) really need to know what else is out there for the safe and efficient control of some of our pests. Bt is (as Morz says) a NATURALLY OCCURING bacterium strain that is entirely species specific. Bt-i infects various larvae in the Diptera insect order (gnats, flies, mosquitoes, etc.). Bt-k is effective against caterpillar pests. There are other Bt strains, all which occur in nature. They do not (cannot) harm other creatures. They work by being ingested into the gut, where the flora can go to work....but only on the insect species that is suseptible to infection from that particular strain of bacteria.

When a person has a large collection of indoor plants, it becomes pretty important to address a pest problem quickly, efficaciously, AND safely. Gnatrol is absolutely one of those products that fills that requirement.

Eileen, fungus gnats (as you have observed) thrive in potting mediums that stay overly moist. The problem 'may' be with the potting mix you are using, have you thought of that? If it is too fine textured and overloaded with peat and not enough coarse material, it is much more apt to stay mucky and moist. Just perfect for fungus gnats to breed in. Many of us add other components to our potting mix to make sure that it is very coarse, and will not readily hold on to an excess of water. (Just a thought.)


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RE: Fungus Gnats

Rhizo, I guess it's my fault..I don't do much reading on insecticides since I'd rather not use them..I'm sure you've read my posts before and note I only use natural stuff. Thank God, but I've been fairly lucky considering the number of plants I have and lack of bugs. I must have a plant angel watching over my plants..LOL.
When it comes to FG's, I again do it naturally..keep soil dry and air circulation using a fan. So far, in the last 20 yrs, 98% of my plants haven't died due to bugs..about 8 or 9 yrs ago I had a banana that died from mealy..actually I tossed it..Last winter I brought in an olive tree that had scale..some of my citrus caught these monster bugs, but they're now gone. When it comes to mites, white fly, I use my concoction of soap, etc. Toni


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RE: Fungus Gnats

Toni, I'd rather go the natural route, but since Gnatrol sounds so safe and effective I may give it a try. I have 2 cats, so I understand your concern for your birds. (How lovely that you breed them, it must be so enjoyable!) Rhizo, you are absolutely right about my soil being overloaded with peat..any suggestions for what I could add to the soil to make it coarser? I use Miracle-Gro Potting Mix which has continuous release plant food added. It is very fine textured. I am still fairly new to plants, but am considering trying my hand at individualizing my soil for each plant (quite a task, but I love anything to do with plantcare!) I can research this in my growing collection of plant books. I'm usually not satisfied with the soil or the size of the pots the plants I buy come in, and usually repot when I get them home. If anyone knows of a good book on plantcare that includes guidelines for soil requirements of specific plants, I'd love to hear about it. I'm sure most of you have been creating your own soil mixes for years, but I still have a lot to learn! Thanks again to all of you...Eileen


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Eileen, yes it's fun raising birds, but work too..lol..so far I've 3 eggs in one nest..I am very careful what I use around them..like I said, even house cleaners can kill a bird. I may be over-protective but can't help it..(S)

I make my own soil, too. I use 1/3 all purpose, 1/3 peat, and 1/3 sand. Plus a couple handfuls of Perlite. Then let soils dry between watering. The sand and perlite help w/well-draining soil so it doesn't stay constantly wet. I use this mix for most plants..though some get more peat, and plants like cactus and succulents gets more sand and less peat. It all works out in the end. Good luck ridding those gnats..Toni


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RE: Fungus Gnats

Wow, this explains a lot. I thought my problem was mold. I had some strange looking, round-white things on the surface of the soil (under decorative polished stone) and coming out the drainage holes. I repotted and even now I am still seeing browning even on newer growth. Ever since I have had this plant I have noticed a few gnats flying around the office. I never knew they were in the soil. Combination of both gnats and mold? Possibly. No strange smells, plant is growing new leaves in force but some look sick from the get go.


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RE: Fungus Gnats

Matty, if you're getting mold and gnats, then you're keeping soil too wet. It needs to dry out more. Do you have a regular watering routine or water when soil is dry? It should only be watered when the first 3" are dry.
Even though decorative stones are pretty, it seems gnats find the perfect living quarter when in wet soil and under shelter. It'll probably be best moving the stones, and cleaning them off..then make sure your soil is dry before watering. It's not an easy task checking soil when rocks/moss is atop. Toni


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RE: Fungus Gnats

Toni...you still don't understand, I don't think. Bt IS absolutely natural. 100% natural. Much more so than some of the stuff that you use! It is NOT an insecticide, in the sense that you mean it. I mean, plain ol water is an insecticide when we use it to drown insects, lol! All I am saying is that you need to have an understanding of Bt, and how it works.

Not that you need it....you are very good at finding alternative methods to control problems.

Believe me, I am SOOOOOOOOOOOO aware of the hazards of common household products. I have a chemical sensitivity. I have had to 'de-toxify' our home of nearly all cleaning products, ordinary shampoos and soaps, scented candles, air fresheners, on and on and on! WHAT a PAIN!!! Of course, the heavy duty pesticides were banned years ago! So, you can trust me on the Bt. ;-) Okay? I'd not steer you wrong.


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Rhizo, I feel terrible about you..My God, you really do have sensitivities! How do you clean, or wash your hair? How do you de-toxify your house? What did you have to do? Be careful what you use..Toni


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RE: Fungus Gnats

:-) Luckily, there are plenty of great, non-toxic products out there. House and hair are squeaky clean, lol!


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RE: Fungus Gnats

I'm totally new to this forum, and I'm pretty new to growing houseplants. I've been searching on how to get rid of my fungus gnats too, and I'm glad I found this web site. I looked up Knock Out Gnats and it says to avoid contact with eyes, skin, and clothing:

http://www.gardensalive.com/article.asp?ai=614

I also wondered if the Miracle Gro potting soil I bought was contributing to the fungus gnat problem. I looked up Miracle Gro Potting Soil and found this (look under the insect link:

http://www.miraclegro.ca/faq/#5_2

I didn't know about sterilized soil versus nonsterilized soil. I'm a little worried about using the Knock Out Gnats too, just because of the label directions. Have any of you had success letting the soil dry out completely and repotting the plants in sterilized soil? I'm just worried there'll be a stray gnat that finds its way into the new soil. Any suggestions?


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RE: Fungus Gnats

Fungus gnats are a result of over watering. Let your plants dry out more and you won't have a problem. No way would I go to the trouble of repotting everything and most bagged potting soils are sterile.

BT IS a totally natural safe way to kill various insect larvae. Just because the label says not to put it in your eyes or rub it on your clothes and skin doesn't mean it isn't safe to use.

I have 7 ponds/water features that I use it in for mosquito larvae control and my cats and wild birds and squirrels have been drinking out of them safely for years. BT is the active ingredient in Mosquito Dunks which are safe for use in horse troughs and dog bowls too.


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RE: Fungus Gnats

I have been growing lots of plants from a seed, and using various store-bought soils like Miracle-Gro etc. In the past I have had problems with storebought soil and their guaranteed fungus gnats. So this time I looked up how to prevent them and went with the microwaving the soil method (50% power for 15 min) Nevertheless, it's so easy for even one to find its way in if someone gives you cut flowers or you open a window. So of course I got infested. It was crazy -- in no time I had tons of visible clear skinny fungus gnat maggots in the soil, not to mention tons of flying adults. Drying out the soil doesn't work b/c they can suspend their development to wait for moisture to return. Plus my plants were using a lot of water.

I tried everything else: dishsoap solution, BTI, hydrogen peroxide, rubbing alcohol, cayenne, etc. Nothing made a difference.

THEN I read about hot water. Yes, simple hot water! You might think it will damage/burn your plants but no, they tolerate it very well. What doesn't tolerate it at all are the fungus gnat maggots! If you don't believe me, you can test it yourself -- pluck a few out of the soil when they come to the surface at night. Put them in a dish and put some hot water on them. They die instantly.

How hot? Hand hot. In my apt, it's as hot as the water is allowed to get. But the temp is one that doesn't burn you but it's too hot to keep your hand under the faucet for more than 15-30 at a time.

To apply to plants, you dont need a lot. Just enough to cover the entire surface and take a few seconds to soak down through. With small pots, maybe a 1/2 cup or a cup.

I've tried this on all my plants (marigolds, irises, morning glories, vincas, four oclocks, mint, basil, pansies, petunias, impatiens, snapdragons, etc.

I was so excited about the results, I had to post -- this is my first post! But just a few days ago I had complete infestation in several pots (pulled out 20 maggots each and still had tons more writhing around). ONE treatment of hot water wiped them out almost entirely -- there are even very few adults left now b/c no babies are taking their place. But I will keep it up in case they are laying any eggs.

p.s. Yellow sticky traps work really well too to catch the adults.


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Orange, I will try the hot water, if no one has any reason why I shouldn't. I have been using yellow sticky traps with great success and allowing my plants to dry out a bit more between watering. The soil I use (Miracle Gro with fertilizer already added to it) may have a lot to do with it, as it is very fine textured and stays wet for a while. I just repotted my gold dust plant and added a little sand in the hopes of coarsening up the mix a bit and providing more drainage.


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RE: Fungus Gnats

I bought my first plant about two and a half weeks ago. I loved it! I watered it every morning, every night, i sprayed the leaves with water all day. Well, You know what happed..little bugs started to fly around the leaves. I thought...it's normal? maybe. So I kept watering it, well more little flies kept flying around the dirt. So, I called Home Depot, since that's where I bought the plant. The lady told me it was normal, to buy RAID for flies and spray it on the plant. I decided to call Calloways Nursery for advice. I told her what I had done: First, I sprayed the top of the plant with a little bit of rubbing alcohol to kill the gnats instantly(read it online). Then I removed the plant from the pot and placed it in my bathtub to let it dry. I also removed all the soil, as much as possible from the root without disturbing them, but I threw away all of the soil inside the pot. I told the lady from the nursery that I had read online about mixxing all kinds of stuff in my soil when ready to repot, like sand, rocks, charcoal, perlite...So I had no idea what to do next. Well, I decided just to go to their nursery to get soil...bough some stone and rocks put them at the bottom of the pot, to avoid blocking the drainage hole....Basically I cannot water it so much! It's like a bamboo plant, but it's not, it's like a dracean(don't know how to spell it) when i bought the plant, it did not have a name. The plant just said "Assorted". In the end, I love asking for help, Im girl I always ask for directions, they helped me...and people in the nurseries always know everything about plants. Home depot they were very nice too, but they were very honest and told me that it was normal for flies to be on my plant and my best bet was to call Calloways. So i did, but i still went online and found u guys...which was a little bit refreshing that i was not alone. Other people's have gone through the same thing as me. Cause, I have a friend, she's older...much older, like 3x older than me...anyways, OMG her Backyard!!!! Gorgeous!!! She lives here in Texas, but when u go to her backyard, u feel like you're somewhere else, Huge palm trees, tropical plants, colorful--bright red, orange, yellow, purple, blue!! all from the same root! ...just crazy shapes, the pedals on the flowers, amazing!! ...simply beautiful...Well, she does travel everywhere...And she did tell me, not to water them so much, but i never listen, always learning the hard way yeah, yeah :p


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RE: Fungus Gnats

chuladas, the overwatering has for now just caused the fungus gnats - but eventually it will kill your plant.
Overwatering is the most common cause of death to houseplants. Get a grip on yourself and STOP WATERING!!!


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RE: Fungus Gnats

( I watered it every morning, every night, i sprayed the leaves with water all day)


chuladas, Oh yeah, waaaaaaay to much water and spraying water too! If all you have is just the one plant, it would have been easier to just change the soil outdoors and hanging up some sticky traps for any stragglers.
No plant that I know of likes to be watered once a day.
Is your plant still living? What plant did you buy?

Billy Rae


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RE: Fungus Gnats

Orangeyouglad: Thanks so much for the hot water tip! I too have a horrible gnat infestion, and like you, have found that drying the soil in between waterings does NOT solve the problem. I just wish I had read this thread before I did my weekly watering routine :(

Oh well, I guess I can live with the nasty bugs for one more week! I'll report back after I give it a try.


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RE: Fungus Gnats

Get a few Sundews! The gnats will get stuck to them and feed them. Plus they are fun and interesting plants! I recommend D. adelae

Check out:

http://www.cobraplant.com/drosera-adelae.html

Tom


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RE: Fungus Gnats

I too have a massive outbreak of fungus gants in ALL of my plants. I have tried Bayer Rose and Flower insect killer. It seems to be nothing but a steroid for the gnats. Each time I use it and return, there are more gnats!!! I have tried a house and garden aerosol spray, no luck. I have now taken a store bought fly strip(the ones in the tube that you pull out)and pulled it out about 3" and tucked it in a hole in the soil next to the plant. Not the most attractive things to be sticking out of your pots but they seem to be catching the aduly flying gnats. I plan to try the hot waterthing for the eggs. Can anyonetell me more about the Alcohol and exactly how to use it?? Will it harm the plant? I will also try the misquito disk. Thank you to all who respond. I am new to the hobby of plants and I have gotten so much good advice from this site.


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RE: Fungus Gnats

Ca, you've used quite a few insecticides in your soil..all I can say is Wow..
For flying/hopping insects, Yellow Sticky Traps work best. It's a non-chemical trap safe around pets and children, and the plant. They're sold in nurseries..Ebay also has great deals on these traps.
Yellow attracts bugs.. they land, stick and die.
I don't know how fly traps work...do they contain insecticides/chemicals?
Make sure the fly traps are safe using indoors..I remember they discontinued certain fly traps several years back..if yours contain chemicals, be careful..read instructions and ingredients.
After ridding fungus gnats, the object it to keep plants insect free. FG's like wet soil and dry air..Improve the environment. Add more humidity by 1. using a humidifer while heat's turned on, 2.use trays w/stones filled w/water, and 3. misting/showering/hosing.
Water soil well, but allow to dry before adding more.
In winter, it's difficult providing fresh air indoors..If the temps are above 50F, open a window a while each day..I use a ceiling fan and/or a small floor fan kept on low, aiming air flow away from plants. Good luck, and remember, it could be worse..Mealy is one bug I can't tolerate. Toni


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RE: Fungus Gnats

hopefulauthor, I guess I am not leary around chemicals. We raise crops and cattle and chemicals are just an everyday thing around here. I try to buy ones that are fairly safe when I can but most of the time there isn't that much harmful stuff in them unless you plan to drink it straight from the bottle. I do practice common sense washing hand and plants before use and not spray on food surfces. I hope I didn't offend anyone. I just enjoy growing things and I HATE bugs. Thanks for all the safe chemical tips. I am willing to try the safer ones.


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RE: Fungus Gnats

I also began using the miracle grow potting soil, organic. I've never had fungus gnats until I started using it. I'm convinced that's where the gnats come from and I'll now try the hot water treatment and BTi if that doesn't work.
Go to gardensalive.com and check out the You Bet Your Garden link on the right side half way down. This guy has a show on national public radio and is a gung ho organic gardener. He almost never recommends conventional pesticides but does recommend BTi for fungus gnats. Check out his archives for a lot of good advice.

M


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RE: Fungus Gnats

Hi everybody,

I grow houseplants in a nyc apt and noted these buggers in my room a few months ago. My all-purpose bug spray for plants wasn't very effective, and I got some sticky fly tape to hang in my room. I figured out what they were, read this particular thread for information, and reduced my watering from occasional to very minimal to keep my plants alive. The situation seemed somewhat under control - there would be atleast 4-5 flying around the apartment and I had to change the tape every month or so, but overall the situation was annoying but not too bad.

Then one day I woke up with a swarm around my face. They were EVERYWHERE. Masses died on my bed, on my shelves, around my planters, and I just refused to sleep in my room for a whole week. The ick level was on par with watching a cockroach crawl across my pillow one night. Fortunately, the swarm seemed to be a one-time outbreak, because the levels of these gnats seemed to drop dramatically (mostly onto my bedsheets and blankets that needed to be washed multiple times). Maybe I don't have enough plants to support that many gnats for long.

Anyway, I finally ordered Mosquito Dunks (BTi) from amazon, but couldn't wait and also got some from a nursery. Put a little chunk into my watering jugs, and since mid-September I have been using water that has had atleast an overnight soak with a chunk of BTi. The lady at the store also recommended crumbling some on top of my planter soil, and I did that with all of my plants. Also gave some to my roommates to use in case my fungus gnats infested their plants also.

I am proud to say that I haven't seen a single fungus gnat for almost an entire month. People, it really works!

I say, forget the hot water and just go with BTi. BTi is just bacteria, which is all around us anyway, and this happens to be one of the more helpful ones. Definitely implement Toni's tips to help the process along. I know it's going to be challenging to keep my room humid with the winter and heaters coming, so to prevent a recurrence of fungus gnats I think I'm going to continue using the BTi-treated water for my plants for the next few months.

Those of you with this particular annoying and disgusting infestation, good luck and take hope from my story. And let me know if you need any mosquito dunks - even if I water my plants with BTi for 2 years, I'll only get through one dunk. I still have an unopened packet of six that I'm willing to mail out.

Thanks to everyone who's posted here in the past - you helped get atleast one person fungus-gnat-free!


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RE: Fungus Gnats

kuchomucho,

Congratulations!


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RE: Fungus Gnats

I, too, have been plagued by fungus gnats and used most of the suggestions mentioned here so I haven't had a problem with them anymore. But, recently, I heard of 2 ideas I've never heard B4.
1. Add a 1/2 cup peroxide to 1 gal water. That could get expensive if you have a lot of things to water.
2. Add a few drops of pet shampoo with pyrethrines to your water.

Have any of you heard of doing either of these things?
Do you think either of these would work?
I haven't tried them yet but may try #2 next winter when I am growing plants from seeds in my basement under lights.
Thanx for your thoughts on these suggestions, Barbara.


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RE: Fungus Gnats

I always read use this message board for info, but for once I can contribute!

I had an outbreak of fungus gnats in my houseplants last week -- there were about 4 of 15 potted plants in my office that got hit hard. I didn't want to repot everything, so I first put everything outdoors that was infested and let it dry out and hoped that dehydration and other insects would consume them. No luck.

I then tried to cover the dirt with seran wrap to keep flies out and cook the ones on the surface. No luck.

I looked on the web and some people recommended neem oil. Others said you should use sticky tape and a bowl of apple vinegar. Those didn't sound too promising.

Today I bought "Earth Tone - Insect Control" at Armstrong's on the recommendation from the manager. The product has an approved indication for fungus gnats (i.e. the bottle states it kills fungus gnats), as well as a host of other bugs. It is basically canola oil and pyrethrin. I bought the concentrate version, but there is a pre-mixed spray bottle too...

I gave my dried plants a good drink of water and then got a spray bottle with the stuff I bought. After lightly misting the foliage and soaking the top layer of soil, I can say that there are only dead bugs. Hooray! I misted one bug to see how quick it would work and the little bugger died in about 10 seconds.

The product is marketed as "organic," not that I care. Toxins are toxins, natural or not.

I will follow up in a few weeks and let you know if any of the plants died, foliage burned, or bugs returned. I am hopeful.


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RE: Fungus Gnats

Do fungus gnats occur in any of Al's mixes? I doubt it considering how well they drain. I have been gradually trying to change over from my traditional media to the gritty mix. I am lucky in that I have access to both DE and tuface. I am sure the DE would be death to fungus gnats but as fast as the traditional mix (with turface)drains, does it matter? The turface cost me a little less.
I used bacillus last fall when bringing my plants indoors and kept up with it for about a month. I thought I had broken the fungus gnat cycle and quit watering with the bacillus. Well, I am regretting it now because the gnats have taken over again recently.
Also, what about other pests? I wonder if a largely inorganic mix like the gritty mix would discourage the mealy bugs and scale I occasionally get on my citrus. I know less about their life cycles than I know about fungus gnats.
Kyle


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RE: Fungus Gnats

Since switching over to a gritty soil (very similar to Al's gritty mix), I have only noticed an occasional fungus gnat, and that may be due to the few plants that have not yet been switched over. I don't think fungus gnats are anything to worry about with a mix like this. I would not, however, count on it to eliminate mealy bugs or scale since those feed on the plant itself rather than soil organics. Though a plant growing in a well aerated soil will be healthier and more resistant to pests. I still see a few mealy bugs on my plants here and there, but they are more manageable this year than last. I also started using a silicon supplement (Dyna-Gro Pro-Tekt 0-0-3), which is supposed to make plants stronger and more resistant to pests and environmental stresses, so that could be helping as well.


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RE: Fungus Gnats

will keeping a plant in a large master bathroom area make it more prone to gnats? it is above our stand up shower on the platform over it.

we just replanted a pothos from a water filled vase into a new pot with new potting soil. this happened one month ago. we only watered at that time. never since.
but that plant now has a great gnat infestation.

we also replanted another pothos at the same time, from a different plant, in a different room, different pot.

now in another room away from shower and it has s few gnats
which may have found their way from the bathroom.

or maybe not.

could the larva have been in the potting soil when we bought it last month?


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RE: Fungus Gnats

Swb, tropicals love humidity, so if your bathroom has high air moisture, your Pothos should be happy, but when a room is humid, the next important thing is air circulation.

Fans work, but there's nothing better than fresh air from outside..Opening a window is the answer.
A/C in summer and heat in winter dries the air.

Have you ever gone to a green house? Notice they use huge fans for air circulation, yet gnats find homes in soil.

Make sure soil dries before rewatering. Constant moisture is a haven for gnats. Roots rot if soil is kept moist all the time anyway, even if gnats weren't the problem.
You mentioned potting into a new pot. Does the pot have drainage holes? A pot and saucer?

When soil is purchased, even though the bag says, sterile, anything is possible. I've found milipedes in newly purchased soil, but this was long ago. You'd think, nowadays, if something is printed on a bag/box it'd be true. What type of soil did you buy? Toni


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'There is no safe chemical.....

.... only safe ways of using chemicals'
ca77le has made a number of assertions in his/her post which I am obliged to point out are all only partly true. Take the first sentence.
"hopefulauthor, I guess I am not leary around chemicals."
Well, we all ought to be! And I am not talking about only those chemicals which we use in the line of the work we do.
I invite anyone to take a bottle from under the kitchen or bathroom sink and read the label critically; google the terms which you do not understand and I am willing to bet something good that you will have a different perspective on that product and you will treat it a bit more cautiously.
And I do not write this because you have offended me in any way. Nor do I write this to be critical of you or anyone else.
It is just that I have dealt with all sorts of chemicals and have seen death and chronic illnesses that have been associated with exposure to chemicals.
I have concluded that the root cause of improper use of chemicals is the complacency which comes with familiarity.
Indulge me as I quote an example. We used to treat corn with thallium sulfate to kill rats on a field scale. I once asked the person who did the mixing if he would eat a grain of the treated corn for $10.00. His reply was, "Skipper, for 25 cents I'd do it!" He had been doing the job for about five years and had got comfortable around the chemical. Never mind that he had lost every strand of hair on his body (and yes, we checked), a definite and definitive symptom of thallium sulfate exposure. At school our heads were dusted with DDT for lice. I am certain that whatever quantity of dicloro diphenyl trichloroethane found its way into the fatty tissue of my body at that time is still there today so please forgive me; I am extremely leery about exposure through my skin, digestive and respiratory systems.
And so I will repeat ad nauseam the line I believe should anchor our attitude to chemicals.
"There is no safe chemical; only safe ways of using chemicals"
Recently I have seen a similar statement in the pharmaceutical industry, "Every drug has side effects".
I will now step down from my soap box.


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RE: Fungus Gnats

Hi everyone,

I'm new to growing/maintaining houseplants. I have two (2) Difenbachia's and (1) Evergreen. I planted them a couple of months ago with Miracle Gro Potting Mix and Miracle Gro Moisture Control (both purchased from Home Depot).
I kept seeing these bugs flying around my home, I must admit that I have a fear of bugs, I didn't know at first where they were coming from until one of my children noticed these "maggot" looking things crawling in the soil of one of the plants. Subsequently, I started my online search and found that I have Fungus Gnats (FG). I have spent a lot of $ on pesticides to find that nothing really works, I haven't watered my plants in 30 days (I truly don't know how they are still surviving but I guess they are in this war with me...lol) even a local exterminator place had nothing to help me to resolve this problem. I did find that the yellow sticky traps worked great but I got the creepy crawlys everytime I looked at all those FG on the stickies.
My local green house offered to re-pot all of my plants, at a fee of course. However, a week ago I read all the messages on this forum and decided to try the top layer of sand. I haven't seen a FG since (one week) even though, I had a very bad infestation.

My questions are: If the adult FG laid eggs in my soil before I applied the sand, what is going to happen to the larvea that is beneath the sand layer? Will they die and it will be the end of my problem or will they emerge from the sand? Should I give my plants some water now or wait another 2 weeks to see if the FG are gone?

Could someone please help me, I'm panicking and don't want to take the next step which is to throw the plants away and never have live plants again!


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RE: Fungus Gnats

While overwatering will encourage fungus gnats, underwatering won't get rid of them. I've let plants get so dry they wilted and had significant dieback, but it still didn't solve the fungus gnat infestation.
There's a common myth that they're only found in the surface layer of soil. Not true; they also use the bottoms of plant pots, entering and exiting through the drainage holes. And it is even less easy to get the soil to dry out there without killing the plants.

There are many great ideas up thread..You can also do this..

Water with a solution of Bacillus thuringiensis, an organic control for caterpillars, to kill insect larvae. Bacillus thuringiensis (or Bt) is a bacteria and is safe to use around children and pets. I think mosquito dunks would be very helpful for you..

You could drench the soil with a solution of pyrethrin, an organic pesticide made from chrysanthemums.

You could use yellow sticky traps placed near the infested plant to catch adult fungus gnats. They work!

The adults cause no damage to healthy, mature plants but are a nuisance inside the house. They will hurt young ones though..They eat the fine roots and rob nutrition from them..You can make your own sticky traps by spreading tanglefoot onto stiff yellow paper.Always try the least toxic method of pest control as your first step.Although Bt is organic and safe to use, it will kill all types of caterpillars, including butterfly larvae. Spray only the plants that are affected.Never use chemical pesticides inside.

Oh yes, you can put a half inch layer of sand on top of the soil in the pot. This will tend to dry out quickly and the fungus gnats will not survive in this dried out top layer. Once they are controlled, you should remove the sand. But remember as I said, watch to see if you have any coming out from the bottom of the pots..;-)

Hope this helpes..


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RE: Fungus Gnats

Once the soil is dry, mix 1 part hydrogen peroxide (H2O2) solution with 4 parts water. Use 3% solution, which you can find in any drug store or in the hygiene/medicine aisle of a chain grocery store. You can use a stronger solution if you change the water mixture appropriately, and don't be too concerned with proportions; it would take a very high concentration of H2O2 to hurt your plants. Just make sure you buy pure H2O2 with no chemical additives
Water your plants as you normally would, using the hydrogen peroxide solution and taking care to get good coverage of the entire top layer of soil. Use a spray bottle if desired. The soil will fizz for a few minutes after application; this is natural. The gnat larvae die on contact with the H2O2. After a few minutes the fizzing stops and the H2O2 breaks down into oxygen molecules (which your plants don't mind) and water molecules (which your plants love).


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RE: Fungus Gnats

Thank God, my plants do NOT, nor have they ever had gnats..even though gnats are the least problems of all insects..Still, who wants them?

If I found a plant that had gnats, I'd bring it outdoors, toss the soil, hose the roots and leaves, scrub the pot or replace, then repot in fresh, well-draining soil.
Last. the plant would get a hearty drink of water. In the future, I'd make sure soil is properly watered.

If 'plants' had gnat 'infestation,' I'd do the same, 'soil is costly, but my plants are worth it,' AND, scrub walls and floor where plants live..

Toppings, such as moss would be tossed in the trash or in the outdoor compost.
When I worked at a plant store, and shipments came in, plants covered with moss, '98% of the time,' were infested with gnats.
Even Spanish Moss, which looks nice, would be removed.

Mike, I'm not sure, but I doubt sand would kill gnats..you might not see them at first, but my fear would be they're liviing underground, munching roots..YUCK!

Since I don't use chemicals, the only way to rid these underground creatures would be to repot in fresh soil, use cleaned pots, then in the future, watered properly.

Gnats visit when soil stays wet and air is dry. I've seen them flying around nurseries, winter and summer.
Not green houses so much, but enclosed stores that sell plants. Because there isn't much humidity to speak of, not to mention fresh, circulating air, employees drenching soil, voila, fungus Gnats. Just my opinion..lol..Toni


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RE: Fungus Gnats

  • Posted by mpr 4 (My Page) on
    Sun, Nov 28, 10 at 22:02

I had this problem with a simple indoor rubber plant. Gnats would periodically fly around and I assumed that's where they came from, since the soil is where they always come from. I tried so many different chemicals, home-made remedies...nothing worked. I even dried that thing out until I got nervous that it would die. I had the problem for about 3 months.

Then I was in my kitchen one day and saw some dead gnats by my cabinet under the sink. I opened the cabinet and moved some items around and they started flying out more than I've ever seen. After inspecting the contents in the back, I found out where they were coming from; a bag of Miracle Grow "Moisture Control" planting soil! It wasn't from my plant at all.

I believe those types of soil have so many additives that eventually they spawn all kinds of creepy creatures. After talking with a couple of "purists" in my area, they've convinced me to stay away from the novelty soil and go with straight potting soil. Their argument was that it's been working for thousands of years in the wild and way before today in homes, and I'm inclined to agree with them. I've been gnat-free ever since.


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RE: Fungus Gnats

MPR..Please don't take this the wrong way, but instead of replying to a 4+ yr old post, you should start fresh.
Some people get upset when/if they get emails from old posts.
I don't think Eileen has an account anymore, but it's best to start or stick with new threads.
Again, I don't mean to offend, Toni


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RE: Fungus Gnats

  • Posted by mpr (My Page) on
    Tue, Nov 30, 10 at 20:03

No offense taken. I really didn't have anything new, just a follow-up. My info would make more sense in context to this thread.

I guess I'm not sure how it could be a problem anyway. This post started in 2006, then jumps from Aug. 2006 to Nov. 2007, then again from Nov. 2007 to Mar. 2009, and there wasn't a problem then.


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RE: Fungus Gnats

Well I suppose maybe I'll get criticized for posting to an old thread too, but - it seems a lot more handy and useful to have all the information on a topic in one place, than to do a GardenWeb search for "fungus gnats" and get 2 or 3 dozen different threads with who knows how much overlap, redundancy, etc. And if people don't want to get emails for old posts, then they should turn off the email notification option. Frankly I've never used it, I get enough emails as it is.

Plus, too often people post something about "the hot water cure" or something like that, but then never follow up with the results - maybe a ping from a post in the past will remind them to let others know how things turned out (so we don't waste our time with ineffectual solutions).

The reason I'm writing is to add to others' speculations about commercial soils such as Miracle-Gro -- we had a bad case of fungus gnats in Vermont, where I'd only used Miracle-Gro soil. Then we moved to California this past spring; I got rid of all houseplants (as you're supposed to do in moving to CA). Got some plants for my office, along with new pots and more Miracle-Gro soils -- and now I've got the darn things buzzing about my head literally as I type this from my office.

So, to avoid libel laws I won't say that Miracle-Gro was the *cause*. But, I will say that there seems to be a lot of correlation between fungus gnats and Miracle-Gro, based on both my experience and the experience of others posting above.


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RE: Fungus Gnats

I got a 10 year old elephant ear for free,brought it home and when winter came took it inside and 1month later I noticed these little things flying around.I thought they were fruit flys.then a month later I was moving the top soil around and saw these very tiny maggots,I flipped because I love plants and enjoy them,THESE THINGS HAD TO GO!!!!! I did some research then.Hung up a couple yellow sticky traps and mixed ALL SEASONS SPRAY OIL with water(way less than recommended)and the next day there were a lot of them on top of the soil dead.2 months have gone BUY and I haven't seen anything.they might be down below.let u know what happens


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RE: Fungus Gnats

I'd like to know if anyone had any luck with the hot water treatment. Anyone?


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RE: Fungus Gnats

I had two (2) avocado plants which were at tall as my ceiling and full of large long leaves. I move the plant to cut the height down and gnats came from the plant in swarms. I used peroxide straight, apples, Dawn mixed with half water did the best to attract the gnats...the HOT water in the rails rather than peroxide, as a exterminator told me to do...
wasting cases of peroxide over the time...
Dawn was the best I found, after using everything recommended....I'm still worried to start anything new.


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RE: Fungus Gnats

I'm not any expert on these gnats, but I have a little bit of them inside and never noticed any harm from them. They LOVE water! I once left my water dish after painting and next day there were tons of gnats drown in it. When they started getting annoying I put a large tray with water in my living room, and wow - there were tons and tons of them there in a few days! I didn't even know I had so many! and now I barely see them flying around. I have over 50 plants in my small house. :)


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