Fungus Gnats

[420oclock]

Anyone have any tricks for getting rid of fungus gnats? I use fly paper, yellow cards, dunks, etc. I also fumigate my flower room in between grows with bug spray. BUT, no matter what I do, at some point I begin finding the little fuckers.

Do they get into my grow via potting soil?

 

[Boss]

They can come in soil.

 

[420oclock]

They can come in soil.

Hmmm. Sounds like the title of a camping porn movie.

That was kind of what I figured. Well, they aren't doing much harm, and I keep their numbers low, guess I'll "live and let live". Now spider mites would be a different story!

 

[Smokin Moose]

Gnats are often a sign of your medium being too wet. I have used a pyrethrum rinse to get rid of them.

 

[sfhaze]

predator nematodes are available at many grow shops, they are easy to apply. The ones I've used are called gnat patrol and come on a sponge.

 

[Racefan]

Gnatrol works well for the babies and the yellow insect cards work well on the flies. Put a layer of sand or perlite over the top of the medium to block access to adults. If the moms can't get to the soil to lay eggs they can't multiply.
I used peroxide at a high dose to kill off my last infestation. Fungus gnats can destroy a crop. The babies eat on the roots and the adults are known to feed on plant juices (suck at the leaves) at times as well.

 

[420oclock]

Thanks for the recommendations guys. Between all the things I'm doing, there are only a few adults around. Think I'll pick up some predators on my next hydro-shop run.

 

[420oclock]

I ran across a good article on fungus gnats:

From:Welcome to the Minnesota Department of Agriculture

Description
Fungus gnats (family Sciaridae) are found in and around damp areas such as wet floors or benches with decaying vegetable matter, algae, and/or fungi present. Adult female fungus gnats lay eggs in soil or growing media. The eggs hatch into larvae that feed on plant roots. As their name suggests, the wings of adult dark-winged fungus gnats appear light to dark gray.
Unlike houseflies or other kinds of flying insects, adult fungus gnats tend to remain near plants (in indoor situations) at soil level and can be found resting on leaf litter and foliage. Larvae dwell in the soil until they pupate; they are legless and have transparent bodies with distinctly black head capsules. Pupae are difficult to detect without magnification, but are stouter and more brown than larvae.
Life Cycle
Female adult thrips deposit oval eggs under the soil surface. The following are the life stages and their approximate duration*:
1. Egg (hatch in 4-6 days)
2. Larva - four instars (10-14 days)
3. Pupa (5-7 days)
4. Adult (lives about 7 days)*
*Adult females can lay up to 1000 eggs in a lifetime!
Damage
Fungus gnat larvae feed on various parts of plant roots and generally diminish plant health. Plants infested with fungus gnat larvae can show signs of stunted growth. Larval feeding can also spread plant pathogens and/or make plants more susceptible to disease. Although adult fungus gnats can help spread pathogens, they do not feed on or otherwise harm plants and are considered a nuisance when they occur in indoor settings such as offices, malls, and apartment buildings.
Control Strategies
Monitoring for adults. Regular monitoring for winged adults using yellow sticky cards will help identify a fungus gnat infestation in its early stages. Disturbing the foliage of plants suspected to be infested will cause fungus gnats to leave plants, and can help trapping efforts. Trapping alone is not recommended as the sole means of control, but when used in conjunction with other methods can reduce significant numbers of adults.
Physical and cultural controls. Do not overwater plants. Keep growing areas as dry, algae-free and weed-free as possible. Pull and bag weeds that may harbor pests. For office and home situation with a relatively few number of plants, cover entire soil area with plastic wrap to prevent adult emergence and egg laying.
Chemical controls. Although the use of insecticides to control fungus gnats on small numbers of indoor plants is not recommended, pyrethrins or pyrethroids may provide short-term relief from adult gnats. (See Physical and cultural controls.) For commercial growing operations, consider adding a biological insecticide such as Bacillus thuringiensis subspecies israelensis to growing media. For more information, consult your local pesticide product dealer to see what works best for your situation.
Biological Control. Several species of beneficial nematodes are available to help keep fungus gnat larvae in check. Other predators such as rove beetles (family Staphylinidae), ground beetles (family Carabidae), and soil centipedes (family Geophilidae) may occur naturally in your growing area. Predator mite Hypoaspis miles and biological insecticides such as Bacillus thuringiensis can be applied to growing media to control fungus gnat larvae. Consult a supplier of biological control agents to see which agents will work best for your situation.
Predators. Soil-dwelling predator mite Hypoaspis miles; rove beetles such as Atheta sp. (family Staphylinidae).

Parasitoids. Synacra pauperi parasitizes the larval stage of fungus gnats. (Note: S. pauperi is not yet commercially available in the U.S., but is being used in Europe for fungus gnat control in mushroom houses.)
Nematodes. Steinernema carpocapsae or Steinernema feltiae nematodes attack the soil stages of fungus gnats. Consult with a supplier of beneficial nematodes to find out how to apply nematodes and about other beneficials that can be used in conjunction with nematodes for additional control.

 

[Boss]

Nice find dude ;-)

 

[Racefan]

Bacillus thuringiensis subspecies israelensis = GNATROL.
I did learn that other than laying 1000 eggs the adults are harmless. Wonder what they do feed on if it isn't plants?

 

[420oclock]

Well, my fungus gnat situation has resolved for now. Although I seemed to only have a minor infestation, I went all out addressing the problem. My grow room has a gravel floor, so spills are not a problem, but I do have seasonal problems with moisture.

I used BT (subspecies israelensis) and will continue to use it on a regular basis. I cleaned up my grow room (good advice in general), getting rid of any dead organic material. I also placed a HotShot no pest strip for 24 hours. My fresh yellow cards are staying clear (for now).

 

[kickstart]

Where does one find these hotshot NPS strips? I have the gnats now...

 

[Boss]

They should be at any hardware store or even at the grocery store.

 

[Cannapheliac]

Gnatrol if you could get it. Its semi illegal in California but it duz work!
I can't get gnatrol so I use a combo of yellow sticky traps and a good pyrethren spray like don't bug me and spray bi weekly to keep em off the buds and use fungus gnat nematodes they eat the larva which is what causes the damage they eat the little feeder hairs off the roots! Lil bastards!! I really hate bugs with a passion I really wish there was like some hi tech way to put up a invisible bug forcefeild!!

 

[Harry Red]

Where does one find these hotshot NPS strips? I have the gnats now...

The fungus gnats I get laugh at no pest strips. That's not to say that having a few in your growing areas isn't a great idea, it is! But, there's a good chance it won't cure your fungus gnat problems and it's not an organic approach to the problem.

You have to break the cycle of adults laying eggs in soil to hatched larvae to new emerging gnats, which requires a multi-pronged attack.

For killing larvae check out Mosquito Dunks . They contain the same active ingredient as gnatrol (Bacillus thuringiensis subspecies israaelenses). They are cheap and available just about everywhere. One dunk can treat 100 feet of water surface so a little piece of a dunk will go a long way. I drop about a 1/8 of chunk down in a gallon of water and let it sit for 48 hours, then mix that at a ratio of 25% to 75% fresh H2O. You can remove the chunk, let it dry and use it again. If using soil, water with the 25%/75% solution once and month and it will kill off the gnat larvae. I've also read that predator nematodes, as Cannapheliac mentioned, are great for killing off the larvae... if you can find and afford them, that is...

For adults, just use victor fly ribbons: They work well on lots of other flying insets as well.

You can also form a barrier over the soil surface to keep the adults from landing, tunneling and laying eggs. Some people use a layer of sterile aquarium sand but that may cut off some oxygen to the roots. I've found a layer of perlite will work about as well and provide more oxygen to the soil. I've read where some people stretch pantie hose over the buckets to keep the adults out so that may be another option for you.

Another organic approach is to apply Food Grade Diatomaceous Earth ( DE ) Powder - 6 oz. to the surface of the soil. The shell particles of the DE are sharp enough to cut the adult and emerging gnats to pieces and kill them. You really don't want to inhale this stuff or get it in your eyes so be careful when applying. It's non-toxic though and can be ingested by humans and animals to kill worms and other parasites.

That's about the end of my experience and research on the topic. Hope it helps and good luck!!

Harry

 

[FreakNature]

Thanks Harry, and everyone else...this is good research and I'll put it to good use.

 

[Ganjarden]

I used a couple different ways at once to fix this problem. I had sticky traps, used a pyrethrum spray and covered my soil and pots so adults couldnt get back in. It solved it in about a week and a half to 2 weeks to being bug free.

 

[SublimeSmoker]

I believe I am having a problem with these fuckers. I hate them. I've had a problem with them before but at another location. This summer I had no problems. Now this winter I do. I have gnatrol on had but it's about 2 years old. I have been using about 3 teaspoons per gal of water and watering my soil with this mixture. Do the adults make the tips of the oldest fan leaves brown and curl almost like it's a magnesium def? I use fox farm ocean forest soil and never had to use nuts until the flowering stage. I'm just afraid where this has gone on for about 2 weeks they will be shocked and I won't have a good female to male ratio. Is it ok to spray you leaves with a little bit of dawn and water like I've heard before?

 

[Andrew W]

Fucking terrorists! I read a post some time ago where a lady said carnivorous plants worked for her. I got some @ Beautiful Carnivorous Plants for Sale. No terrariums required!

Lots of info on the site. I thought the Tropical plants would work best in a grow room.

I choose these:
Introductory Tropical Sundew Collection #1 : Beautiful Carnivorous Plants for Sale. No terrariums required!

In about a week the fucking gnats were sleeping with the virgins https://www.420magazine.com/community/styles/420style/smilies/thumb.gif

 

[Supernaut]

I was having a problem with them as well.

Here's what I did:

My plants in flower need water every other day. On the dry day, I cut slices of potato about 1/4" thick and placed them in each pot right after the lights came on. The slices stayed in there for 24 hours when the lights came on again and I had to water. I removed the slices and put them quickly into a plastic bag (I could see the larvae on them when I looked really well and I didn't want any to jump off). Then I watered as usual. I repeated the process 2 more times and haven't seen a single one flying around or stuck to my yellow cards around since.

I also read that watering with H202 would kill the larvae on contact. I would have resorted to it if the potato didn't work well enough.