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Fruit fly/Fungus gnats.

Shorerider

Shorerider

Staff Member
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Extreme Member
While watering my seedlings in my grow box I notice fruit flies emerging from the soil. Not many, maybe 4-5 over 70+ plants.

They don't seem to be causing any harm as yet but would like to know if they could. Obviously once I have pods on my plants they'll be outside in my garden.

It seems as though a couple of security guards (see link) have taken up residence in my grow box so they should control numbers somewhat.

https://db.tt/USVgyYYF


Cheers....
 
Wow what a battle, I'm glad you won in the end. Hopefully I don't get to that stage. I've had a look online and it looks like I can't get Mosquito dunks here in Aus. I may have to try the adhesive strips and or h2o2.
 
Shorerider said:
Wow what a battle, I'm glad you won in the end. Hopefully I don't get to that stage. I've had a look online and it looks like I can't get Mosquito dunks here in Aus. I may have to try the adhesive strips and or h2o2.
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Do you bottom water? If not, that is your biggest defense. I had them super bad 2 years ago like PT and the strips worked best along with the sand but sand was late. This year I started with the sand and never had issues. 
 
LordHill said:
Is sand on top of the soil a good option even if you top water?
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Not really unless you can do it really slow so that you do not wash sand away. With sand on top when you bottom water the sand turns into a very hard crust, impossible for those annoying gnats to get into the soil. 
 
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No, I top water. I have quite a few seedlings so what would be the best way to bottom water all of them at the same time?
 
If you notice my picture above all those cups are in a tray, I pour 1 gallon of water in there and everyone gets bottom watered through the cutout holes int he bottom of the cups. This also works for containers that already have bottom drainage. 
 
Ah, I see. Do you allow all plants to gradually soak all the water up, or do you drain off any excess water after a given time?

I went out and bought some of this: http://ecoorganicgarden.com.au/products/pest-disease/eco-neem/

It was the only product that mentions fungus gnats.

Then I read on their web site that it is only approved for use on ornamentals In Australia.

Has anyone had any experience with this product?


Cheers......
 
Shorerider said:
No, I top water. I have quite a few seedlings so what would be the best way to bottom water all of them at the same time?
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Stop top watering right now. Joyners system is what I use. I let them drink all they can in 20-25 minutes then a quick drain.
 
The gnats are all about the top inch of soil so keep that dry!
 
And diatomaceous earth on the surface works well. They hate it!

Shorerider said:
Wow what a battle, I'm glad you won in the end. Hopefully I don't get to that stage. I've had a look online and it looks like I can't get Mosquito dunks here in Aus. I may have to try the adhesive strips and or h2o2.
Click to expand...
 
Get the strips up ASAP!
 
PrimeTime said:
 
Stop top watering right now.
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Careful with this advice, Pythium is a real pain in the ass.
 
 
PrimeTime said:
 
 
 
The gnats are all about the top inch of soil so keep that dry!
 
 

 
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You guys do know that the fungus gnats don't have any problem finding the bottom watering holes right? I mean, they fly around looking for moist soil......
Like Chris, I had a real problem last year. This year my approach was mosquito dunks and sand and perlite (same use as sand) and lots of fly paper. No issues over the winter.
 
IMHO, bottom watering can be worse than top watering if the roots don't go down that far.
 
I haven't watered in 48 hours and my cups are starting to dry out. I will leave them for another 12 hours for now. I now have sand and will be adding it to every cup. I plan to water with the Eco-neem that I bought and have also added fly paper.

Fingers crossed this works.

Thanks for the help guys. What started out as what I thought was a silly question turns out to be much more serious.

Goes to show that the only silly question is the one that you don't ask.


Cheers.......
 
I dont know if its the same as small flies i did have, but i used a small bowl with vinegar, water and zalo (soap), they go after the smell and when they try to land on the water they drown. I do the same inside when we get small flies in the kitchen.
 
pwb said:
I dont know if its the same as small flies i did have, but i used a small bowl with vinegar, water and zalo (soap), they go after the smell and when they try to land on the water they drown. I do the same inside when we get small flies in the kitchen.
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The ones in the kitchen are fruit flies and that works for them and fungal gnats, however, if and when the fungal gnats lay eggs on the soil, the babies eat all the roots. 
 
If you want to make that trap better, put clear wrap over the top of the bowl and poke small holes using toothpicks. Once they go in they cannot come out and will hit the liquid no matter what! 
 
H2O2 from the bottom, 1/2 in or more dry sand on the top.
 
I've used it straight out of the bottle (3% standard solution) but others mix it down.
 
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