Fungus Gnats

farmergiles · 08-10-2011, 06:35 PM

These pesky varmints are present pretty much everywhere on the Earth, from Antarctica to hot deserts.
They are most common in forests, swamps or anywhere there is moisture.
They are almost always found where there are houseplants.

The family of gnats most commonly found in growrooms are called sciaridae. There are thousands of different varieties but many of them are very similar in appearance and behaviour.

Fungus gnats have a life cycle of around a month, going from egg to larva to pupa to adult fly to death in that time.

The female adults lay eggs, about 100 or 200 per gnat. The eggs hatch into larvae after about 4-6 days.

The larvae live in soil or other moist media and feed on fungus, decaying vegetable matter and plant roots.

After 12-14 days, the larvae pupate for another 3-6 days before emerging as adults.

The adults have wings and can fly. Most of them are female. They live for about 7-10 days.
The adults do not feed but they probably will need to drink water.

Normally the gnats won't cause that much damage except to weak plants, especially plants which have problems with their roots.
However they can act as a vector (carrier) for disease and mould.

Also they have a bad habit of laying eggs on freshly sprouted seeds or the bottom of the stems of unrooted clones with fatal consequences when the larvae hatch.

farmergiles · 08-12-2011, 01:55 PM

The adult fungus gnats are pretty easy to see. They are typically about 4mm long.

The larvae can be seen in the soil (or other medium) sometimes, they are about the same length.

In soil it is unusual to see the pupae and almost impossible to see the eggs.

The first means of defence used by many gardeners is the sticky yellow trap. This is just a flat piece of yellow material coated with some kind of sticky substance.
They can be purchased from garden centres. They are easy to make, I just use squares of yellow plastic material coated with oil. Anything will do so long as it is yellow and sticky. Flying insects are attracted to the colour yellow for some reason.

Hang them close to the plants.

Here are some stuck gnats on a trap. Mwuhahahaha!

Sticky traps are great because if you there are any flying insects in a grow, a few will almost always get stuck before they are seen flying around.
So the grower is alerted early to the presence of flying pests and can see what type they are.

They will only catch the adult flying fungus gnats. The eggs, larvae and pupae all live in the soil.
The traps probably wouldn't catch all the flying gnats in any case.

If you have ladybugs you might not want to use sticky traps as they will catch the ladybugs

.

farmergiles · 08-12-2011, 03:00 PM

The adults can also be controlled with insecticides. Soap spray works fine.

Sticky traps etc will keep the adult numbers down. But to eliminate fungus gnats it is necessary to mess up their life cycle at an earlier stage.

Neem or pyrethrum drench can be applied to the soil to kill the larvae. Pyrethum should not be used too close to harvest, even though it is an organic product. Always follow the product safety instructions on pesticides.
The gnats use the top part of the soil and the soil exposed by the drain holes to lay their eggs so this is where most of the larvae and pupae are found.

Bacillus thuringiensis is a bacteria which can be introduced to soil when watering. BT will kill fungus gnat larvae as well as many other insect larvae. It is very effective- pyretrum or neem can tend to lose efficacy as gnats can become resistant to them.
Bacillus thuringiensis is harmless to humans and plants and many beneficial insects such as bees. So it can be used with abandon right up to harvest.
A BT product might be available from garden centres but most likely would need mail ordering.

farmergiles · 08-12-2011, 03:20 PM

Fungus gnats need moist media like soil to lay their eggs in and for the larvae to live in.

They get into the soil from the outside, the soil at the top of a pot or around the drain holes will be the areas they tend to lay their eggs in.

If these areas are dry the gnats will struggle to lay eggs and the larvae will find it hard to thrive.

Overwatering encourages them.

Perlite or sand or some other quick drying substrate can be used to cover the top of the soil and fill the drain holes at the bottom.
Because it will dry out quicker than the soil after watering, it will present a dry inhospitable habitat for the gnats.

Some people use diatomaceous earth (DE) for this purpose- it dries out the exoskeleton of insects killing them horribly. Haha!
Care should be taken not to suffocate the plant with DE. So the DE should be removed after a few days once all the larvae and gnats die.

farmergiles · 08-12-2011, 03:34 PM

Assemble the following -

A tin
Some damp paper tissue
Clingfilm or a clear plastic bag big enough to cover the top of the tin
An elastic band.

Place tissue in tin. Leave out in grow.

Return after a day or two. There will be many gnats in the tin, laying eggs in the wet tissue.
Dexterously place the bag/film over the top and secure it with the elastic band so they can't escape.
Remove gnats and get rid.

They tend to prefer the tissue to the soil so this can be repeated until all the gnats are gone.

thanks to Brick Top

**Pharm Girl** · 09-07-2011, 09:40 AM

.........when all fails...this is what happens!

TheGodDegree · 10-20-2011, 08:49 PM

I currently have these annoying bastards in my garden. At first it was clear that they were there, but it wasn't bad at all. Then it got real bad, and then they disappeared. Now there are some, but not many. Haha.

I tried using square pieces of plastic coated with Vaseline. Figured this would work. Didn't work at all. Not one of them has stuck onto it. Is there something about Vaseline they don't like? Also, one of my local grow shop owners told me that it isn't much to worry about in the later stages due to the root growth, and as they get bigger, the bugs are less effective. No idea if this is true, but it seems like he is right. Btw, I am using an aeroponic/hydroponic setup using hydroton, not soil. Not sure if that makes a difference either.

Either way, I was surprised that the Vaseline idea didn't work. I'm just gonna go out and buy the ones they sell at the store.

farmergiles · 10-21-2011, 01:15 AM

I'm surprised the vaseline trap doesn't catch at least some of them. Engine oil works ok for me.

Fungus gnats don't decimate your crop like mites or something but they can act as a vector for mould and disease, also they do sometimes kill newly sprouted seeds and fresh cuttings.

Soap spray will kill the adults.

Vacuuming them helps keep the numbers down and it's kinda fun.

TheGodDegree · 10-21-2011, 09:17 PM

I like the vacuuming idea. I could see getting all baked out and trying to catch fungus gnats with a Shop-Vac, haha.

**slunt** · 10-22-2011, 08:48 AM

I've seen terrible crop damage due to fungus gnats that got in during the early stages. The plants were diverting more energy to root repair than to flower growth. It only got worse when the second more numerous generation hatched out in the 4-5th week.
Prevention like usual, is the key.
If they get into new clones consider that crop a write off, as far as useful yields are concerned.
New sterile room with new sterile soil is a must after a gnat infestation.
really great info FG. Understand the enemy and then defeat them.

like_clockwork · 10-29-2011, 07:48 AM

Yeah i bought i bag of soil from lowes to mix with my foxfarm and it came with a whole dynasty of fungus gnats free of charge. i found the easiest way to kill them is to just spray my plants with water and then they start flying around and i kill them with my hands. took a few days but all gone now.

Bobbito Blaze · 10-29-2011, 08:04 AM

Clock work they lay larvae in wet soil so wetting the soil actually attracts them drying out your soil will prevent them from laying eggs in soil so don't be surprised if they show up in a few days the best solution to get rid of these guys and I tried alot of methods most effective was bacillus thuringiensis var. Israelensis but is really hard to get and expensive about $300 a gallon for the pure form however if you can find those mosquito dunks there a round doughnut looks like kitty litter compressed into little rings you put them in bird baths swimming pool tarps or any where water builds up and give skeeters a place to breed it also has the strain of the bacteria u need break o little off one put it in your water can and water plants it kills the larvae and no more knats it's a great perminate solution

headsrnice · 12-19-2011, 05:56 AM

These little pests have began to show their face.. put up some sticky fly paper, have a couple soda cans with oil and moistened paper towels. Gonna give the soil a spray of insecticidal soap. Hoping this will get rid of the bastards!

headsrnice · 12-21-2011, 06:29 AM

Well I am really thinking that the reason my girls have been growing so slowly is the larvae and youngins of the fungus gnats destroying my roots. Seems like growth over the last couple weeks has been non-existant There's a ton of them that fly up when I water, and some of the bottom leaves are being damaged by the adults sucking on them.

Not sure if I should just count my loses with these, clean house and start again?

farmergiles · 12-21-2011, 09:02 AM

You might consider using mosquito dunks (google it).

Also - a variation on the sticky trap- line the top rim of the pots (inside and out) with tape and make it sticky (oil, anything sticky will do but don't contaminate the soil with anything bad).
Because the gnats almost always crawl over the rim when they are coming or going, this should catch a lot more of them than with hung sticky traps.

Picture provided by Pa-Nature

I think gnats can be beaten using simple techniques. Don't give up yet headsrnice.

headsrnice · 12-22-2011, 03:10 PM

Got the stick traps on the edges of the pots and sprayed the soil down with some insecticidal soap. Seems to be under control.

Those sticky papers were covered though!!!

seansplace · 12-30-2011, 12:37 PM

Nice bit of info nice one FG, will be keeping my eye out for these pests and putting in place the edge of the pot method before they start to prevent i think

Roach · 12-30-2011, 02:30 PM

Quote:

with tape and make it sticky

use double sided tape.

Bobbito Blaze · 12-31-2011, 05:40 AM

Hate those fuckers they stick to buds like fly paper and is gross

08-10-2011, 06:35 PM	#1 (permalink)
farmergiles Yahookan Join Date: Sep 2006 Location: Sick of the hatred and the lies Posts: 7,807 Thanks: 2,285 Thanked 3,750 Times in 2,554 Posts	Fungus Gnats These pesky varmints are present pretty much everywhere on the Earth, from Antarctica to hot deserts. They are most common in forests, swamps or anywhere there is moisture. They are almost always found where there are houseplants. The family of gnats most commonly found in growrooms are called sciaridae. There are thousands of different varieties but many of them are very similar in appearance and behaviour. Fungus gnats have a life cycle of around a month, going from egg to larva to pupa to adult fly to death in that time. The female adults lay eggs, about 100 or 200 per gnat. The eggs hatch into larvae after about 4-6 days. The larvae live in soil or other moist media and feed on fungus, decaying vegetable matter and plant roots. After 12-14 days, the larvae pupate for another 3-6 days before emerging as adults. The adults have wings and can fly. Most of them are female. They live for about 7-10 days. The adults do not feed but they probably will need to drink water. Normally the gnats won't cause that much damage except to weak plants, especially plants which have problems with their roots. However they can act as a vector (carrier) for disease and mould. Also they have a bad habit of laying eggs on freshly sprouted seeds or the bottom of the stems of unrooted clones with fatal consequences when the larvae hatch. __________________ Cultivate a stoic calmness *Fuck the Monkeys* Every Kind of Vice

08-12-2011, 01:55 PM	#2 (permalink)
farmergiles Yahookan Join Date: Sep 2006 Location: Sick of the hatred and the lies Posts: 7,807 Thanks: 2,285 Thanked 3,750 Times in 2,554 Posts	The adult fungus gnats are pretty easy to see. They are typically about 4mm long. The larvae can be seen in the soil (or other medium) sometimes, they are about the same length. In soil it is unusual to see the pupae and almost impossible to see the eggs. The first means of defence used by many gardeners is the sticky yellow trap. This is just a flat piece of yellow material coated with some kind of sticky substance. They can be purchased from garden centres. They are easy to make, I just use squares of yellow plastic material coated with oil. Anything will do so long as it is yellow and sticky. Flying insects are attracted to the colour yellow for some reason. Hang them close to the plants. Here are some stuck gnats on a trap. Mwuhahahaha! Sticky traps are great because if you there are any flying insects in a grow, a few will almost always get stuck before they are seen flying around. So the grower is alerted early to the presence of flying pests and can see what type they are. They will only catch the adult flying fungus gnats. The eggs, larvae and pupae all live in the soil. The traps probably wouldn't catch all the flying gnats in any case. If you have ladybugs you might not want to use sticky traps as they will catch the ladybugs . __________________ Cultivate a stoic calmness *Fuck the Monkeys* Every Kind of Vice

08-12-2011, 03:00 PM	#3 (permalink)
farmergiles Yahookan Join Date: Sep 2006 Location: Sick of the hatred and the lies Posts: 7,807 Thanks: 2,285 Thanked 3,750 Times in 2,554 Posts	The adults can also be controlled with insecticides. Soap spray works fine. Sticky traps etc will keep the adult numbers down. But to eliminate fungus gnats it is necessary to mess up their life cycle at an earlier stage. Neem or pyrethrum drench can be applied to the soil to kill the larvae. Pyrethum should not be used too close to harvest, even though it is an organic product. Always follow the product safety instructions on pesticides. The gnats use the top part of the soil and the soil exposed by the drain holes to lay their eggs so this is where most of the larvae and pupae are found. Bacillus thuringiensis is a bacteria which can be introduced to soil when watering. BT will kill fungus gnat larvae as well as many other insect larvae. It is very effective- pyretrum or neem can tend to lose efficacy as gnats can become resistant to them. Bacillus thuringiensis is harmless to humans and plants and many beneficial insects such as bees. So it can be used with abandon right up to harvest. A BT product might be available from garden centres but most likely would need mail ordering. __________________ Cultivate a stoic calmness *Fuck the Monkeys* Every Kind of Vice

08-12-2011, 03:20 PM	#4 (permalink)
farmergiles Yahookan Join Date: Sep 2006 Location: Sick of the hatred and the lies Posts: 7,807 Thanks: 2,285 Thanked 3,750 Times in 2,554 Posts	So what can I do to prevent fungus gnats? Fungus gnats need moist media like soil to lay their eggs in and for the larvae to live in. They get into the soil from the outside, the soil at the top of a pot or around the drain holes will be the areas they tend to lay their eggs in. If these areas are dry the gnats will struggle to lay eggs and the larvae will find it hard to thrive. Overwatering encourages them. Perlite or sand or some other quick drying substrate can be used to cover the top of the soil and fill the drain holes at the bottom. Because it will dry out quicker than the soil after watering, it will present a dry inhospitable habitat for the gnats. Some people use diatomaceous earth (DE) for this purpose- it dries out the exoskeleton of insects killing them horribly. Haha! Care should be taken not to suffocate the plant with DE. So the DE should be removed after a few days once all the larvae and gnats die. __________________ Cultivate a stoic calmness *Fuck the Monkeys* Every Kind of Vice

08-12-2011, 03:34 PM	#5 (permalink)
farmergiles Yahookan Join Date: Sep 2006 Location: Sick of the hatred and the lies Posts: 7,807 Thanks: 2,285 Thanked 3,750 Times in 2,554 Posts	A gnat trap- Assemble the following - A tin Some damp paper tissue Clingfilm or a clear plastic bag big enough to cover the top of the tin An elastic band. Place tissue in tin. Leave out in grow. Return after a day or two. There will be many gnats in the tin, laying eggs in the wet tissue. Dexterously place the bag/film over the top and secure it with the elastic band so they can't escape. Remove gnats and get rid. They tend to prefer the tissue to the soil so this can be repeated until all the gnats are gone. thanks to Brick Top __________________ Cultivate a stoic calmness *Fuck the Monkeys* Every Kind of Vice

09-07-2011, 09:40 AM	#6 (permalink)
Pharm Girl Weeding the Garden.~ Join Date: Feb 2006 Posts: 4,540 Blog Entries: 13 Thanks: 3,003 Thanked 1,176 Times in 894 Posts	.........when all fails...this is what happens! Attached Images __________________ .....The Time has Come to 'Walk the Talk'.....~ ......A message for ALL from the Deer Tribe...~ It is a great journey — but you must do the walking and have the willingness to change and make the leap into the next level of human evolution. Become an inquisitive free thinking individual that takes responsibility for your life and the spiritual accountability to live life to the fullest. *Fuck the Monkeys*

10-20-2011, 08:49 PM	#7 (permalink)
TheGodDegree YaHookan Join Date: May 2008 Location: USA Posts: 157 Thanks: 7 Thanked 67 Times in 46 Posts	I currently have these annoying bastards in my garden. At first it was clear that they were there, but it wasn't bad at all. Then it got real bad, and then they disappeared. Now there are some, but not many. Haha. I tried using square pieces of plastic coated with Vaseline. Figured this would work. Didn't work at all. Not one of them has stuck onto it. Is there something about Vaseline they don't like? Also, one of my local grow shop owners told me that it isn't much to worry about in the later stages due to the root growth, and as they get bigger, the bugs are less effective. No idea if this is true, but it seems like he is right. Btw, I am using an aeroponic/hydroponic setup using hydroton, not soil. Not sure if that makes a difference either. Either way, I was surprised that the Vaseline idea didn't work. I'm just gonna go out and buy the ones they sell at the store. __________________ "All mankind is divided into three classes: those that are immovable, those that are movable, and those that move." - Benjamin Franklin

10-21-2011, 01:15 AM	#8 (permalink)
farmergiles Yahookan Join Date: Sep 2006 Location: Sick of the hatred and the lies Posts: 7,807 Thanks: 2,285 Thanked 3,750 Times in 2,554 Posts	I'm surprised the vaseline trap doesn't catch at least some of them. Engine oil works ok for me. Fungus gnats don't decimate your crop like mites or something but they can act as a vector for mould and disease, also they do sometimes kill newly sprouted seeds and fresh cuttings. Soap spray will kill the adults. Vacuuming them helps keep the numbers down and it's kinda fun. __________________ Cultivate a stoic calmness *Fuck the Monkeys* Every Kind of Vice

10-21-2011, 09:17 PM	#9 (permalink)
TheGodDegree YaHookan Join Date: May 2008 Location: USA Posts: 157 Thanks: 7 Thanked 67 Times in 46 Posts	I like the vacuuming idea. I could see getting all baked out and trying to catch fungus gnats with a Shop-Vac, haha. __________________ "All mankind is divided into three classes: those that are immovable, those that are movable, and those that move." - Benjamin Franklin

10-22-2011, 08:48 AM	#10 (permalink)
slunt Super Moderator Join Date: Aug 2004 Location: Peoples Republic of Kanada Posts: 319 Thanks: 55 Thanked 743 Times in 189 Posts	I've seen terrible crop damage due to fungus gnats that got in during the early stages. The plants were diverting more energy to root repair than to flower growth. It only got worse when the second more numerous generation hatched out in the 4-5th week. Prevention like usual, is the key. If they get into new clones consider that crop a write off, as far as useful yields are concerned. New sterile room with new sterile soil is a must after a gnat infestation. really great info FG. Understand the enemy and then defeat them. __________________ i have heard there are troubles of more than one kind. Some come from the front, some come from behind. Bur I've bought a Big Bat. I'm all ready you see. Now my troubles are going to have troubles with me!(Seuss)

10-29-2011, 07:48 AM	#11 (permalink)
like_clockwork YaHookan Join Date: Oct 2009 Location: Juan valdez's backyard Posts: 54 Thanks: 19 Thanked 13 Times in 8 Posts	Yeah i bought i bag of soil from lowes to mix with my foxfarm and it came with a whole dynasty of fungus gnats free of charge. i found the easiest way to kill them is to just spray my plants with water and then they start flying around and i kill them with my hands. took a few days but all gone now.

10-29-2011, 08:04 AM	#12 (permalink)
Bobbito Blaze YaHookan Join Date: Oct 2011 Posts: 166 Thanks: 2 Thanked 62 Times in 51 Posts	Clock work they lay larvae in wet soil so wetting the soil actually attracts them drying out your soil will prevent them from laying eggs in soil so don't be surprised if they show up in a few days the best solution to get rid of these guys and I tried alot of methods most effective was bacillus thuringiensis var. Israelensis but is really hard to get and expensive about $300 a gallon for the pure form however if you can find those mosquito dunks there a round doughnut looks like kitty litter compressed into little rings you put them in bird baths swimming pool tarps or any where water builds up and give skeeters a place to breed it also has the strain of the bacteria u need break o little off one put it in your water can and water plants it kills the larvae and no more knats it's a great perminate solution

12-19-2011, 05:56 AM	#13 (permalink)
headsrnice YaHookan Join Date: Jun 2010 Posts: 323 Thanks: 274 Thanked 61 Times in 46 Posts	These little pests have began to show their face.. put up some sticky fly paper, have a couple soda cans with oil and moistened paper towels. Gonna give the soil a spray of insecticidal soap. Hoping this will get rid of the bastards!

12-21-2011, 06:29 AM	#14 (permalink)
headsrnice YaHookan Join Date: Jun 2010 Posts: 323 Thanks: 274 Thanked 61 Times in 46 Posts	Well I am really thinking that the reason my girls have been growing so slowly is the larvae and youngins of the fungus gnats destroying my roots. Seems like growth over the last couple weeks has been non-existant There's a ton of them that fly up when I water, and some of the bottom leaves are being damaged by the adults sucking on them. Not sure if I should just count my loses with these, clean house and start again?

12-21-2011, 09:02 AM	#15 (permalink)
farmergiles Yahookan Join Date: Sep 2006 Location: Sick of the hatred and the lies Posts: 7,807 Thanks: 2,285 Thanked 3,750 Times in 2,554 Posts	You might consider using mosquito dunks (google it). Also - a variation on the sticky trap- line the top rim of the pots (inside and out) with tape and make it sticky (oil, anything sticky will do but don't contaminate the soil with anything bad). Because the gnats almost always crawl over the rim when they are coming or going, this should catch a lot more of them than with hung sticky traps. Picture provided by Pa-Nature I think gnats can be beaten using simple techniques. Don't give up yet headsrnice. __________________ Cultivate a stoic calmness *Fuck the Monkeys* Every Kind of Vice Last edited by farmergiles; 01-01-2012 at 03:17 PM. Reason: added pic

12-22-2011, 03:10 PM	#16 (permalink)
headsrnice YaHookan Join Date: Jun 2010 Posts: 323 Thanks: 274 Thanked 61 Times in 46 Posts	Got the stick traps on the edges of the pots and sprayed the soil down with some insecticidal soap. Seems to be under control. Those sticky papers were covered though!!!

12-30-2011, 12:37 PM	#17 (permalink)
seansplace YaHookan Join Date: Dec 2011 Location: mars Posts: 215 Blog Entries: 2 Thanks: 102 Thanked 39 Times in 31 Posts	Nice bit of info nice one FG, will be keeping my eye out for these pests and putting in place the edge of the pot method before they start to prevent i think

12-31-2011, 05:40 AM	#19 (permalink)
Bobbito Blaze YaHookan Join Date: Oct 2011 Posts: 166 Thanks: 2 Thanked 62 Times in 51 Posts	Hate those fuckers they stick to buds like fly paper and is gross

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