# dealing with fungus gnats



## ehanes7612 (Nov 25, 2011)

quite by accident found a way to control fungus gnats while insulating greenhouse

drape some plastic from the top sides of greenhouse so that there is a gap between walls and plastic sheeting...the gnats fly up into the space and where the condensation collects, atracts the gnats and traps them (this also helps with insulation)


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## SlipperFan (Nov 25, 2011)

Do you have a photo, Ed?


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## ehanes7612 (Nov 25, 2011)

SlipperFan said:


> Do you have a photo, Ed?



tried taking a photo but cant tell anything from it..basically its just two sheets of plastic with a gap in between them


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## Lanmark (Nov 25, 2011)

But do they breed there, too, and repopulate the greenhouse? Just wondering.

I've had luck using Spinosad.


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## ehanes7612 (Nov 26, 2011)

Lanmark said:


> But do they breed there, too, and repopulate the greenhouse? Just wondering.
> 
> I've had luck using Spinosad.



they get stuck to the water condensed on the plastic , and because the plastic is moving, at those points where there is water the plastic sticks to the walls of the greenhouse, trapping the flies ..they die their..its like a natural fly paper...it works really well..and since i did this the number of flies has dramatically decreased


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## likespaphs (Nov 26, 2011)

Lanmark said:


> ...I've had luck using Spinosad.




really?
it's not labeled for gnats


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## Clark (Nov 26, 2011)

For the last six weeks, have started light garden in mancave.
The enclosure has basement window within.
Foundation walls are cooling off now, and are condensation magnets.

Gnats are collecting just like yours. But only around the window.
Just found sticky traps today. Will apply also.


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## likespaphs (Nov 26, 2011)

a couple home remedies

http://www.learn2grow.com/problemsolvers/insectsanimals/insectdamagecontrol/fungusgnats.aspx

http://www.ehow.com/how-does_4761302_gnat-trap-work.html


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## Lanmark (Nov 26, 2011)

likespaphs said:


> really?
> it's not labeled for gnats



Yes it has worked great for me. I use Captain Jack's Deadbug Brew Concentrate. It has worked great for me in controlling thrips, fruit flies and fungus gnats.


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## likespaphs (Nov 26, 2011)

Capt Jack's is labeled for thrips and fruit flies, but not fungus gnats. if you are getting control of gnats, it may for some other reason. (i've never had it impact a population of fungus gnats.)
don't forget to rotate your pesticides otherwise they will lose their efficacy


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## Lanmark (Nov 26, 2011)

likespaphs said:


> Capt Jack's is labeled for thrips and fruit flies, but not fungus gnats. if you are getting control of gnats, it may for some other reason. (i've never had it impact a population of fungus gnats.)
> don't forget to rotate your pesticides otherwise they will lose their efficacy



It may indeed be for some other reason. I dunno. It's definitely not on the label but I took a chance. I sprayed and they all dropped dead and didn't return. 
I certainly can't guarantee it will work for everyone. That's very good advice about rotating pesticides -- something we should all be diligent about.


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## SlipperFan (Nov 26, 2011)

Does it soak into the soil and kill the larvae, Mark?


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## Lanmark (Nov 26, 2011)

SlipperFan said:


> Does it soak into the soil and kill the larvae, Mark?



It's definitely a possibility! I had fungus gnats in my mounds of sphagnum moss as well as on my cork mounts and in my baskets filled with hydroton. It doesn't help that I now live in a "reclaimed swamp" 

I drenched everything with a solution of spinosad and sprayed as well. Voilà -- no more fungus gnats! If spinosad didn't do it, I guess Jesus or the tooth fairy might have come through for me. Mass suicide is another option or it could have been some other unknown factor beyond my knowledge and control. :rollhappy:


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## SlipperFan (Nov 26, 2011)

Interesting.

Just because Spinosad doesn't specifically say it's for fungus gnats, that doesn't mean it won't be effective on them. Bayer Tree and Shrub doesn't say it's for mealy bugs, either. Anyway, this is a new insecticide to me. Thanks for the info.


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## likespaphs (Nov 26, 2011)

SlipperFan said:


> ...Just because Spinosad doesn't specifically say it's for fungus gnats, that doesn't mean it won't be effective on them. Bayer Tree and Shrub doesn't say it's for mealy bugs, either....



yeah, but i have never seen a product with spinosad (although i generally use Conserve SC) that is labeled for fungus gnats or their larvae
imidacloprid, the active ingredient in the tree & shrub spray is commonly labeled for mealies (example: Marathon, Merit)


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## Lanmark (Nov 26, 2011)

likespaphs said:


> yeah, but i have never seen a product with spinosad (although i generally use Conserve SC) that is labeled for fungus gnats or their larvae



I haven't either.

Maybe the fungus gnats I had were swamp gnats...is there such a thing?  All I know is that they weren't the same as the fruit flies or the black flies which we get around here. They weren't whiteflies either. They weren't no-see-ums nor any other type of biting fly. They were simply itsy bitsy flies which were in, on and around all of my plants like a cloud. They constantly got into my ceiling light fixtures and died there, looking like black pepper inside the frosted globes when the bulbs were switched on. They looked for all the world to me like any other fungus gnat I've ever seen down through the years.

They were already here when I moved into this place in May, and they quickly colonized all of my plants. I'm soooo glad this problem has finally ended, however it happened. It's been a few weeks now and there's still been no recurrence.

Perhaps _Bacillus thuringiensis_ would be a better option for you, Dot. I didn't happen to have any on hand when I decided to take action, and this is how I came to use the spinosad.


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## abax (Nov 27, 2011)

I've always used Orthene 97% as a drench and placed
sticky traps around my greenhouse to monitor and catch
any gnats that might have been airborne when I drenched.

Yes, I know it stinks.


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## likespaphs (Nov 27, 2011)

abax said:


> ...Yes, I know it stinks.



it also has much higher mammalian toxicity


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## Clark (Nov 27, 2011)

I was hoping Mr. Hanes could hang a lightbulb over the area of concentration.
As day turns to night, will they fly towards the remaining light?
Or, is my window a temp. or O2 thing.


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## SlipperFan (Nov 27, 2011)

Lanmark said:


> ...
> Perhaps _Bacillus thuringiensis_ would be a better option for you, Dot. I didn't happen to have any on hand when I decided to take action, and this is how I came to use the spinosad.


Gnatrol? The problem with that is that it needs a soil medium to work. In orchid potting media, there's really nothing to hold the little critters so they can do their work.

Actually, I've had good luck with Bayer Tree and Shrub when I've used it in a strong enough solution. But as been said before, it's good to change off insecticides.


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## abax (Nov 27, 2011)

Well, I'm the only mammal in my gh and I have my hazmat suit, etc. I look ridiculous, but I feel fairly safe and
my gh is a closed system so nothing gets exposed outside
of the gh.


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## NYEric (Nov 28, 2011)

Really!?! I dont spray for fungus gnats. I have a few sticky traps and hand squash any that escape. I haven't seen a live one in ages.


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## Lanmark (Nov 28, 2011)

SlipperFan said:


> Gnatrol? The problem with that is that it needs a soil medium to work. In orchid potting media, there's really nothing to hold the little critters so they can do their work.
> 
> Actually, I've had good luck with Bayer Tree and Shrub when I've used it in a strong enough solution. But as been said before, it's good to change off insecticides.



Yes, Gnatrol is what I was referring to.

You could always try a pyrethrin aerosol or fogger.


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## keithrs (Nov 28, 2011)

Gnatrol does work but you have inoculate it for 24-48 hrs before use. Hydro guys really like Gognats.


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## ehanes7612 (Jan 10, 2012)

the fungus gnat situation is slowly becoming more of a problem...cant seem to find where they are breeding.. checked many of the roots and they are fine ..no presence of larvae either...but the number of flies is steadily increasing despite flytape...they seem to know what that is now


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## Bob in Albany N.Y. (Jan 10, 2012)

Ed check out this site: 
http://www.hummert.com/ProductList.aspx?C=01B&Title=Total-Release Insecticides

Knock on wood, I haven't had this problem yet, so haven't tried these products. I have however ordered a couple of those aerosol bombs and used them quite successful in the greenhouse. I normally do a bomb once a week in a regiment for two or three weeks.


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## ehanes7612 (Jan 10, 2012)

Bob in Albany said:


> Ed check out this site:
> http://www.hummert.com/ProductList.aspx?C=01B&Title=Total-Release Insecticides
> 
> Knock on wood, I haven't had this problem yet, so haven't tried these products. I have however ordered a couple of those aerosol bombs and used them quite successful in the greenhouse. I normally do a bomb once a week in a regiment for two or three weeks.



thanks but i am not ready to deal with chemicals..trying the potato trick


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## Yoyo_Jo (Jan 10, 2012)

oke: Get some pinguiculas! I swear by 'em.


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## cnycharles (Jan 10, 2012)

if they truly are fungus gnats, they will be drawn to little puddles of water. if you put some greenshield into a wide container of water they will try to land on it and the surface tension is lowered and voila, submarine gnats! whenever we spray greenshield and there are little puddles on the floor, they are very quickly drawn into them and die. physan and greenshield are probably close enough to the same thing that it will work, maybe even soapy water on a cookie sheet will work


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## ehanes7612 (Jan 11, 2012)

cnycharles said:


> if they truly are fungus gnats, they will be drawn to little puddles of water. if you put some greenshield into a wide container of water they will try to land on it and the surface tension is lowered and voila, submarine gnats! whenever we spray greenshield and there are little puddles on the floor, they are very quickly drawn into them and die. physan and greenshield are probably close enough to the same thing that it will work, maybe even soapy water on a cookie sheet will work



unfortunately they do this once and then the others seem to find out whats going on..tried it


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## chrismende (Jan 11, 2012)

The most important thing to do about fungus gnats is to evaluate whether you are watering too much! I get them under those circumstances and they get much better when I back off on watering so much. I also use many pinguicula plants, but these are more as indicators. 
I will try Spinosad, though, myself. I read all the data that DowAgro has on it's site (not that I can truly trust Dow), but it sounds pretty good. Just because something isn't labelled for a specific insect doesn't mean the product won't work for it. Their statement is "controls a wide variety....including..."


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## ehanes7612 (Jan 11, 2012)

chrismende said:


> The most important thing to do about fungus gnats is to evaluate whether you are watering too much! I get them under those circumstances and they get much better when I back off on watering so much. I also use many pinguicula plants, but these are more as indicators.
> I will try Spinosad, though, myself. I read all the data that DowAgro has on it's site (not that I can truly trust Dow), but it sounds pretty good. Just because something isn't labelled for a specific insect doesn't mean the product won't work for it. Their statement is "controls a wide variety....including..."



the watering is down to twice a week...the plants do dry out somewhat...which is even more puzzling ..have checked all the plants and havent found any larvae..trying the potato method to locate them..when i was growing inside i once had an infestation only to find out they were laying eggs in the drainage area below the plants (where media fell out of the pots and piled up)...but the greenhouse floor is clean


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## Shiva (Jan 11, 2012)

A quick shot of Raid will get rid of them, for a while.


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## ehanes7612 (Jan 11, 2012)

I placed potato slices in twenty pots . One pot about ten larvae showed up. I unpotted and sure enough the mix was wet. Found that water from the ceiling was dripping unto the medium creating a wet spot. Will place potato slices in all the pots...but at the rate of adult presence in my GH ..this one pot couldve been the culprit


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## likespaphs (Jan 11, 2012)

if you have a fertilizer injector, you may want to look into parasitic nematodes
they won't do anything to the population of adults but will take out larvae
there are also other benefical insects which can control them, including rove beetles and, dang, i forget the predatory mite
greenmethods.com has lots of good info


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## ehanes7612 (Jan 11, 2012)

likespaphs said:


> if you have a fertilizer injector, you may want to look into parasitic nematodes
> they won't do anything to the population of adults but will take out larvae
> there are also other benefical insects which can control them, including rove beetles and, dang, i forget the predatory mite
> greenmethods.com has lots of good info




i am hoping i found where they breed...my next step was to use nematodes..thanks!


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## likespaphs (Jan 11, 2012)

they can breed just about anywhere, including in the frames of the greenhouse, so i dunno if you'll be able to figure it out without some sort of "all work and not play makes Jack a dull boy" moment


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## ehanes7612 (Jan 11, 2012)

likespaphs said:


> they can breed just about anywhere, including in the frames of the greenhouse, so i dunno if you'll be able to figure it out without some sort of "all work and not play makes Jack a dull boy" moment



yeah BUT.. their larvae still need food and wont pupate unless they can gorge for four days ..the frames of my greenhouse are plastic , SO....unless they eat plastic ..i can negate that possibility...........proverbs aside ..i would still like to constructively think through this problem without giving up or resorting to chemicals and perhaps offer a mechanical alternative to infestation....we will see if it works


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## SlipperFan (Jan 11, 2012)

Lanmark said:


> Yes, Gnatrol is what I was referring to.
> 
> You could always try a pyrethrin aerosol or fogger.



Actually, I looked into that. But the directions say to NOT use if you have an open flame. Thus, of no use in my greenhouse with my gas heaters.

Advice to all: read the directions before purchasing!


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## likespaphs (Jan 12, 2012)

they keep breeding in the gutters of the greenhouse out here


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## ehanes7612 (Jan 12, 2012)

good thing i dont have gutters....there really is no place for them to breed inside my GH except in the pots..now they can breed outside..behind the GH..where i throw the compost...but seems unlikely in the cold weather..but i am not too certain their tolerances for temperature


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## ehanes7612 (Jan 12, 2012)

Think I found all the places they were breeding . Two pots. Managed to kill many gnats with hand clapping method. So hopefully the adults won't be replenished.its fairly easy to find the larvae . They hang out near the top. Just have to be careful to distinguish from young millipedes


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## likespaphs (Jan 13, 2012)

what is your floor?


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## ehanes7612 (Jan 13, 2012)

likespaphs said:


> what is your floor?



concrete


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## ehanes7612 (Jan 15, 2012)

seems what i am doing is working..only counted about five gnats today


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