Fungus gnats. Pain in the arse or total nightmare?

[Lazy Dayz]

Got a few fungus gnats flying around in the grow space. Are these just a bit of a bit of a pain in the arse or are they going to cause me serious problems? I've got 3 or 4 weeks left on this run. Many thanks!

[Nervous]

Depends. 

A few are beneficial because the larva break down organic matter and generally don't cause root issues (they're part of healthy outdoor ecosystems anyway)

If you've given them the right conditions (constantly wet and warm) to thrive and loads of adults are flying about then it's trouble. 

Just get some yellow sticky papers up and if you're growing in organic soil - rove beetles. If you're growing in coco - good luck because the bottled remedies for gnats do fuck all without repetitive (costly) applications, diatomaceous earth works until you water it and sand is often laden with salts.  

Edited November 9, 2020 by Nervous

[Bartyfartblast]

get some of those yellow sticky sheets near soil where they hatch out. 

[Simple Jack]

Fungus gnats are a pain in the arse, but not in the same league as things like mites and thrips which actively devour the plants themselves (and are a bugger to eradicate). They eat the symbiotic fungi that act as an extension of the root system, decreasing nutrient uptake. At this stage though it is unlikely to make a huge difference. You could get some yellow sticky traps to catch the flyers if they start swarming.

 

Ultimately, the best way to avoid fungus gnats is to buy uncontaminated growing medium.

[Lazy Dayz]

Many thanks for the advice @Nervous, @Bartyfartblast& @Simple Jack. I'll get some sticky traps for the little shitbags

[Greenthumbgardener]

Yup got the little fuckers in at mine aswell. As, others have mentioned swerve the liquid bottle treatment 'nuke em' only seemed to nuke my wallet haha! 

 

Got the nematodes about to go in and do there bit for the cause. Also another member said neem oil on top of soil layer worked for them. 

[buddy13]

Steinernema feltiae nematodes

1 application usually does the job but another a week later totally destroys them

[Lux_Interior]

On 09/11/2020 at 8:51 PM, Simple Jack said:

Ultimately, the best way to avoid fungus gnats is to buy uncontaminated growing medium.

 

Interesting! How likely is shop bought compost to have Fungus Gnat larvae in it? Maybe use a Neem Oil drench prior to putting plants into it, as a preventative measure? (!)

[Mestizo]

10 minutes ago, Lux_Interior said:

 

Interesting! How likely is shop bought compost to have Fungus Gnat larvae in it? Maybe use a Neem Oil drench prior to putting plants into it, as a preventative measure? (!)

Very likely.

 

You can put washed sand and cover the top of your medium and also line the bottom of water catchers/saucers. That reduces their path in to the compost to lay more. Is normally sold as play sand for kids in garden centres. You don't wanna use your average sharp or builders sand as it's not washed.

 

Fly traps laid in corners of the grow space give you a good indication of other pest intrusions also. Once you know what you're dealing with, you can treat accordingly.

 

Fungus gnats are a fucking pain in the arse though without a doubt. They came in on the compost I'm using also. I'll still always use compost over things like Coir which is transported air miles. One man eco warrior over here. People bake their spent compost to kill of gnat eggs and then add fungi back in but you know, whatever you can do to get get your herb grown.

Edited November 22, 2020 by Mestizo

[Lux_Interior]

1 hour ago, Mestizo said:

Very likely.

 

You can put washed sand and cover the top of your medium and also line the bottom of water catchers/saucers.

 

Wouldn't a sand covering alter the drainage when watering though, or, maybe mess with pH of the compost/substrate?

[Boojum]

They're a pain in the arse but they don't harm the plants.

 

Get some fly paper from the local hardware shop, hang a roll of it down in the middle of your grow space

[Biokid]

Sticky traps and a layer of PLAY sand (not builders sand it is full of salt).

I bought a bag from BnQ and it has lasted a good few years. Never had any problems with either drainage or feed.

 

Bio

[Lux_Interior]

Just now, Boojum said:

They're a pain in the arse but they don't harm the plants.

 

Get some fly paper from the local hardware shop, hang a roll of it down in the middle of your grow space

 

But don't the larvae, going unchecked, damage the roots? Then nutrient uptake is affected. I had yellowing plants with necrotic spots & I'm fairly sure ignoring the odd Fungus Gnat had something to do with it. I thought it was a Cal-Mag thing but the necrotic spots married up quite closely with what I was seeing on various gardening websites. (Not all indoor gardening webstes)

[Lux_Interior]

6 minutes ago, Biokid said:

Sticky traps and a layer of PLAY sand (not builders sand it is full of salt)

 

That was it, Salt in building sand. Someone the other day said 'Play Sand' (Safe for Kids). I couldn't remember. 

 

Thanks

[mudman123]

damage your roots dey do do dont dey doh. A lot of these becomes lots more real fast. all good sugetions on prevention good luck