Grow Mediums Autopots & Fungus Gnats

[kushedy]

I’ve been running autopots now for a couple of years with coco coir & in general I am fairly happy with them aside from the fact they seem to be prone to fungus gnats, in my experience at least.

I am just doing battle with the little bastards again now. I actually ran one of my grow tents drip to waste this time & that is gnat free. The autopot tent however is gnat central.

In the autopots defence I have been a little slack & not implemented preventative measures.

Do any of you suffer from fungus gnats regularly? Any tips for low cost preventatives?

 

[lunarman]

I have had them too with autopots. But can't say it was because of them. I don't have enough experience with them to say its a problem with autopots. That tray of water might contribute to it.

What I would do to exterminate them now is get some mosquito dunks and grind them up and mix in water. I don't know what ratio. I just winged it. I top watered that solution in to the plants. Also you could take something like 1/8 of a dunk and put it in the autopot tray in the section with the valve. These things are often floated in ponds to kill mosquitios so I figured floating in the tray can't hurt and should help. This should kill the larvae.

But you still need to break the cycle. Then I would get play sand and put a 1/4inch layer on top of each pot. The adults won't be able to get thru the sand and lay more eggs. So that breaks the cycle.

Those two things should get them. Maybe get some of those sticky strips too.

For prevention, I have had good luck mixing in Diatomaceous Earth in to my medium. I mix it in to my coco but then as I load up the pots I stop an inch before the top and put a layer of it there then fill the last inch up with remaining medium. Maybe even layer some more DE on top as well. And/or play sand too. I bought a big ass bag of DE because I use a lot of it now and its way cheaper in bulk. And I don't feel bad using a lot of it.

 

[kushedy]

Thanks for the advice. I've given them a dose of hydrogen peroxide & some DE. Other bug killing things are on order.
I was just curious if it was just me or if others also get this issue frequently with autopots.

I have had them too with autopots. But can't say it was because of them. I don't have enough experience with them to say its a problem with autopots. That tray of water might contribute to it.

What I would do to exterminate them now is get some mosquito dunks and grind them up and mix in water. I don't know what ratio. I just winged it. I top watered that solution in to the plants. Also you could take something like 1/8 of a dunk and put it in the autopot tray in the section with the valve. These things are often floated in ponds to kill mosquitios so I figured floating in the tray can't hurt and should help. This should kill the larvae.

But you still need to break the cycle. Then I would get play sand and put a 1/4inch layer on top of each pot. The adults won't be able to get thru the sand and lay more eggs. So that breaks the cycle.

Those two things should get them. Maybe get some of those sticky strips too.

For prevention, I have had good luck mixing in Diatomaceous Earth in to my medium. I mix it in to my coco but then as I load up the pots I stop an inch before the top and put a layer of it there then fill the last inch up with remaining medium. Maybe even layer some more DE on top as well. And/or play sand too. I bought a big ass bag of DE because I use a lot of it now and its way cheaper in bulk. And I don't feel bad using a lot of it.

 

[Clarky]

Fighting them myself. My pots are full of soil. Covered the top of soil with DE and the damn things just walk through it no problem. Put those yellow sticky strips in each pot and they were covered in a few days. Not sure what to do next.

 

[Waira]

Do any of you suffer from fungus gnats regularly? Any tips for low cost preventatives?

I've had good results with Mosquito granules/ bits,... Bonide and Summit brands are good, and you can get them in smaller jar sizes too... these are biological controllers using Bacillius thuringiensis israelensis (Bti) which the larvae ingest and die by infection of the guts! The larvae are the trouble makers, nibbling on roots,.... adults are little more than flying gonads,... the population has to be pretty bad before it really impacts the plant, some good news there,... sticky traps will cover the adults,.. it'll take some days to make an impact, but once in the soil, the Bti sticks around and keeps killing-
You can make a fast "tea" with this stuff, to activate and start reproducing the Bti quicker... for a gal of water, (no chlorine BTW) in a bucket, use about 1/8 cup granules, add 2T molasses or other carbo' source, maybe a dash of nutes and set it someplace fairly warm at least, room temp or so is fine,... let it brew for a day or so,.. if you have a little aquarium aerator, that's even better, keeps more O2 in there and stirs things around,... then water as usual, no need to saturate the pot, just a good drink is fine...

 

[Proph]

I've had fungus gnats several times. I wouldn't blame any of the pots I've used. Currently in auto pots. Sounds like you may need to do a deep cleaning of the pot system/tent/grow space. We know thar ,ungus gnats love moist soil, so the autopots create a perfect breeding ground, but I can't say the pots are the "cause".. Those larva can stay dormit for months.

 

[puffer1958]

Fighting them myself. My pots are full of soil. Covered the top of soil with DE and the damn things just walk through it no problem. Put those yellow sticky strips in each pot and they were covered in a few days. Not sure what to do next.

Sand works as a barrier, once you stop top watering/feeding

 

[kushedy]

I have just got hold of some sand so I will be filling in the top of my pots with that but only after I have given them a good dusting with some Pyrethrin powder.

For the record this is the list of treatments I have found online as supposedly being effective.

Mosquito dunks/bits

Pyrethrin

Neem Oil

Hydrogen Peroxide

Diatomite powder

Mighty Wash



I have previously used H202 & Neem oil successfully. H202 won’t kill all larvae but it definitely reduces numbers.

I also found that Diatomite powder did very little. Maybe you have to apply a really thick layer rather than dusting?

Mighty Wash may work for anything that gets hit by it as you spray it but I can’t see it working on the larvae.

Neem oil soaks & sprays work but smell to high heaven & eventually gunk up & kill sprayers.

I haven't tried Mosquito Dunks yet as they are not available in my country so I would have to order from abroad which doubles the cost of it at least.

I’ve only got 2 weeks left on the current crop so I am just going to go with pyrethrin powder & sand. I’ll do the same on the next run & see how effective the pyrethrin & top layer of sand is.

 

[Clarky]

Just soaked with h202 and put a thick layer of DE on top. See how that works and let yas know

 

[Clarky]

DE didnt work. Gnats crawled right through the stuff. Laid down about a 1/2 inch of nice blue sand. Hope that works.