Fungus Gnats - Beneficial Nematodes?

Hey All - New here so excuse any ignorance, please!

Have had a few fungus gnats flying around plants.. nothing crazy but took the preemptive strike and have been watering with mosquito dunk dissolving in water bucket as well as sprinkling mosquito bits on top of soil and also mixed some in while replanting... This seemed to do the trick and wasnt getting any adults on yellow sticky paper... I backed off with the dunks (guessing this is where I went wrong) and have noticed over the past few days that the annoying buggers have returned, more than before... Still only a few, but want to make sure I knock them out as the plants are healthy and two weeks into flowering and growing fast/well.

I have started the dunks back up dissolving in water and have sprinkled more of the "bits" on the top of my soil mix... Read that beneficial nematodes (Steinernema Feltiae) are great... ordered some (7 million) on amazon and awaiting arrival... anyone have thoughts on these? I am confident that the dunks will help starve and kill larvae again but dont want to take any chances on my first grow (and hopeful harvest)... I also planned on spraying some SM-90 on plant as foliar as I heard this will help keep the adults from plants and also help prevent any white powdery mildew..

Your thoughts are appreciated on using the Beneficial Nematodes! Also... any fear of SM-90 hurting them? Even if only used as Foliar...?

Please and thank you!!!

welcome to RIU

gnats - i've battled them and i hate them. what did i learn from the battle? it only takes one plant to bring about a gnat apocalypse from bad watering habits. i.e. watering everyone because you're in there when not everyone needs to be watered. find out where your infestation is coming from - you can see the larvae if it's a bad infestation, then you'll know what plant you're over-watering just enough to facilitate a good environment for them to reproduce. nematodes are helpful too. can't help on the SM-90 but someone will be along soon for that one.

good luck on your first grow.

I used a combinations of 1/2 dunk per 5 gal. Before that all the pots of 3 rounds of peroxide. Then while using the dunks I used Diat Earth. The DE helped end it, but I've read sand on top works better?

food grade diatomaceous earth. You could cut off the food source with actinovate or ceylon cinnamon they're anti-fungal. hydrogen peroxide diluted will kill larvae. I would be worried about killing the nematodes.

undercovergrow said:

welcome to RIU

gnats - i've battled them and i hate them. what did i learn from the battle? it only takes one plant to bring about a gnat apocalypse from bad watering habits. i.e. watering everyone because you're in there when not everyone needs to be watered. find out where your infestation is coming from - you can see the larvae if it's a bad infestation, then you'll know what plant you're over-watering just enough to facilitate a good environment for them to reproduce. nematodes are helpful too. can't help on the SM-90 but someone will be along soon for that one.

good luck on your first grow.

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Thanks Undercover Girl! Yes - have read that over watering is also the culprit to this starting! WHOOPS! I have cut back and added 1-2 days extra between watering... Now water/fert (rotate every other) every 3-4 days, unless top inch of soil feels very dry... Hopefully the decreased watering schedule combined with the dunks should work... Still plan on adding the nematodes regardless though as extra precaution..

Dr.Pecker said:

food grade diatomaceous earth. You could cut off the food source with actinovate or ceylon cinnamon they're anti-fungal. hydrogen peroxide diluted will kill larvae. I would be worried about killing the nematodes.

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Thanks again Dr. Pecker! Thinking I will stick with the mosquito dunks and decreased watering for a week or so while adding nematodes, when they arrive and see if they look to disappear... When you say you would be worried about killing the nematodes... are you referring to with the SM-90 or one of the methods you recommended? Is food grade diatomaceous earth organic (believe I found some that is)? Trying to stick to organic for the first grow here... but not always easy... So I just sprinkle ontop of soil? how often do I do this, and how thick..? I do have clay pellets ontop of soil currently to help maintain moisture on top level of soil due to tons of airflow in tent... but maybe this is where some of my problem arose... hmmmmmm Ok to sprinkle ontop of them? Again - thanks for all the help!

Final Phase said:

I used a combinations of 1/2 dunk per 5 gal. Before that all the pots of 3 rounds of peroxide. Then while using the dunks I used Diat Earth. The DE helped end it, but I've read sand on top works better?

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Thanks so much, Final Phase... I may pick up some DE.. if you look at my reply to Dr.Pecker.. appreciate your insight there too!

Nematodes, diatomaceous earth or safers end all caterpillar dust and ease up on the moisture

hells canyon genetics said:

Nematodes, diatomaceous earth or safers end all caterpillar dust and ease up on the moisture

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Thank you much!

GrowNube said:

Thanks Undercover Girl! Yes - have read that over watering is also the culprit to this starting! WHOOPS! I have cut back and added 1-2 days extra between watering... Now water/fert (rotate every other) every 3-4 days, unless top inch of soil feels very dry... Hopefully the decreased watering schedule combined with the dunks should work... Still plan on adding the nematodes regardless though as extra precaution..

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i started watering/feeding from the bottom and it has helped a lot too. good luck.

undercovergrow said:

i started watering/feeding from the bottom and it has helped a lot too. good luck.

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Sorry for ignorance here - what do you mean? How does one water from bottom. Using smart pots and a solid soil mix...

I've battled them many times and have the perfect formula for me at least.

Top dress your soil with Gnatnix growstone. It's made from recycled glass which prevents larvae from emerging and adults from getting into soil to lay eggs.

Then use Gnatrol with every watering.. its just some bacteria that attack fungus gnat larvae in soil. OMRI Organic certified.

Then use smart/air pots instead of regular pots with holes on bottom. The air pots let air in but is fine enough to keep gnats from getting in that way. Then of course what everyone else said about not over watering and giving each plant only enough water it needs.

GrowNube said:

Sorry for ignorance here - what do you mean? How does one water from bottom. Using smart pots and a solid soil mix...

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i use air-pots (soil) and just fill up (to a point that it will cover the bottom half of the air-pot) a 5-gallon bucket and set them inside of it. it soaks up water/nutrients from the bottom up.

undercovergrow said:

i use air-pots (soil) and just fill up (to a point that it will cover the bottom half of the air-pot) a 5-gallon bucket and set them inside of it. it soaks up water/nutrients from the bottom up.

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How many gallons do you prepare for each plant? I have each of three plants in 5 gallon smart pots so finding buckets that will work may be difficult... How long do you leave in there?

GrowNube said:

How many gallons do you prepare for each plant? I have each of three plants in 5 gallon smart pots so finding buckets that will work may be difficult... How long do you leave in there?

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currently using 3-gallon air-pots...yeah, getting ready to use 5-gallons this run so now i have a problem. thanks.

I always start a soil mix with crab shell, BTI and nematodes. Never a prob

Rrog said:

I always start a soil mix with crab shell, BTI and nematodes. Never a prob

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BTI? Sorry - what is that? Thanks and noted for next grow...

infdjedi said:

I've battled them many times and have the perfect formula for me at least.

Top dress your soil with Gnatnix growstone. It's made from recycled glass which prevents larvae from emerging and adults from getting into soil to lay eggs.

Then use Gnatrol with every watering.. its just some bacteria that attack fungus gnat larvae in soil. OMRI Organic certified.

Then use smart/air pots instead of regular pots with holes on bottom. The air pots let air in but is fine enough to keep gnats from getting in that way. Then of course what everyone else said about not over watering and giving each plant only enough water it needs.

Click to expand...

Thanks so much! I am and have been using smart/air pots. love em... If the mosquito dunks don't work, I will try gnatrol... Believe they are formulated from same organic ingredient (bacillus thuringiensis )...

BTI = Bascillus Thuringiensis Israelensis

Same as you're talking with the dunks

Rrog said:

BTI = Bascillus Thuringiensis Israelensis

Same as you're talking with the dunks

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My dude! Thank you!