Whats the best way to get rid of fungus gnats?

Sick Plants & Problems
#28

Got my “Mosquito Bits,” and threw a handful on top of the soil on both my house plants and my Special Plants before watering, and mixed some diatomaceous earth into the soil for plants I’ve confirmed to be infested. For what it’s worth, I haven’t seen any of these little bastards around my house in probably 5 days or so, and haven’t caught any in sticky yellow traps in 3 days.

I’m going to pick up some “Gnatrol WDG,” if/when they come back – think it’s the same bacteria as Mosquito Bits and the dunks, but made specifically for plants.

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#29

I’ve noticed theres a huge difference in Gnatrol vs Mosquito Bits.

Mosquito bits works, Gnatrol doesn’t. Very limited control vs the bits.

1 Like
#30

That is quite the difference! Ha! Ha!

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#31

I’m surprised with all the organic guys here that no one has recommended crab shell meal.

“Neptune’s Harvest Organic Crab Shell (2-3-0) is an excellent dry organic source of nutrients, including Calcium (23%) and Magnesium (1.33%). It retains moisture in the soil and builds the organic matter. It also gives the roots something to grab onto and wrap around, for a food source, creating a deeper root system. Crab Shell is high in Chitin (Kite-en), which promotes the growth of Chitin eating bacteria in the soil. It will help eliminate Ants, Grubs, Fungus and Root Nematodes, because they are all Chitin based in structure. Put around plants, Crab Shell will keep Slugs and snails off. It also helps choke out weeds and keep moles, voles, mice, etc… from digging up bulbs and root vegetables.” 1

Besides all of that ^ the tiny razor sharp shards slice up Fungas Gnat Larvae as they move towards the surface.

Don’t believe me? Try it for yourself.
I haven’t had a fungus gnat in 2 or more years and all I changed was adding crab shell to my soil mixes.

Stay Hazed,
Jake

Source:

25 Likes
#32

You have to get aggressive when controlling FG.

Control watering, no sloppy irrigation… No excessively wet media. FG reproduces quickly if given the right conditions. Keep your greenhouse clean.

I think the more important idea is to target the FG larva, this is done with Bt or Bacillius thuregenesis treatments. AKA Mosquito bits.

Discard contaminated media, if you even suspect its contaminated, treat the entire bag with Bt.
But better to get something clean.

Whats good about BT is they cannot develop resistance to it. (EPA doc) I’ve tried several controls of imichlorprid/malathion/pyrethium by itself, or in rotation. They simply dont break the cycle of reproduction and the media can get recontaminated quickly. They just dont have that residual activity like BT has. Plus I’m a cheapskate. I have a few years supply of Merit 75. but how fast FG can develop resistance to it is frightening. Bt is pretty impressive in how the entire class of dipthera larva is controlled by it.

Mosquito bits when activated you can see mycelium shooting out of the bits and this is exactly what you want. My suggestion for Bt application to the top of soil is no less than 1 bit per sq/cm of soil surface dont be stingy with it. Bt is also harmless to humans and plants, in fact GMO corn “StarLink” cultivar has Bt toxins within the corn itself. Not approved for human consumption, but it has made it into the food chain.

Back to Bt control strategy.

If you are having FG problems, use Bt, Also, consider decontaminating the media itself, I’ve unpotted plants and washed top layers off, to remove the larva, and when I repotted, I put some on the bottom and I topped the ball off with Bt and then topped it off with clean media and applied the bits to the top.

What about the fliers?

I personally use a combination of traps and No Pest Strips. The traps are obviously an instant kill and is used for monitoring, but the NPS dont instantly kill, but I can tell that they have a very erratic flight pattern with NPS in the room. Yes I know dichlorvos are not exactly ideal but it seems to suppress them, you have to use them in a way that is not according to label directions, but when I see control I simply space them out more and more and eventually they go back into the plastic bag to be used if issues develop. In my experience NPS only covers about 5-10 square foot for FG control.

What I do like about BT vs. chemical controls is no worries about residuals, and I can use it even during flower, no worries at all. Ive seen some commercial inoculants using Bt in the formulas.

5 Likes
#33

@Blowingupjake Nice, I’ll have to try that on a soil run in a top dress. If I can have overlapping controls, I’m all for it.

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#34

That is the exact crabshell i have used for six years now. Neptunes harvest is great. I use their kelp also.

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#35

Ah! A fellow Neptune lover!

So… Do you have fungus gnats @ryasco ?

Stay Hazed,
JAake

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#36

Nope. Along with the crab meal I also use diatomaceous earth every transplant. Between the two i have no worries.

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#37

Damn right. I love DE.
“I put that shit on ereything”

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#38

I also use DE.
I sprinkle a little on the surface of my soil when it dries after each watering.
I think it is more of a preventive rather than a traditional insecticide. It kills the pests slowly and it keeps the population of gnats from exploding out of control. It never seems to kill every single one of the renegade bastards. But it certainly keeps them in check, so that they never really become a problem.
I use lots of yellow sticky traps hanging around my garden as well as DE.

5 Likes
#39

@Calyxander

I agree with your observation of DE. In a way it acts like a mechanical barrier, but does does not have good control like other methods. FG can go into every little crevice, and if your sanitation isn’t on point, they can go live there too, I’ve found them in my dehuey drain tray.

Eradication is very difficult. But traps, DE, BT, sanitation, and environmental controls will suppress them to the point of where you dont even see them. One thing that never goes away even after control is gained is the monitoring system that is also used as traps.

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#40

ugh fungus gnats just showed up in my tent recently (coco grow, already 6-8 weeks in to veg) guess i’m off to get some sticky fly traps and what else? DE?

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#41

mosquito dunks/bits ?

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#42

Neem meal, (a pinch or two once a week) DE, (diatomaceous earth) and letting the pots dry out (if not a notill) is the only way i can reliably get rid of gnats. Sticky traps help and beneficial predators help also.

4 Likes
#43

All three sound good :grin: traps really only help you see how many you have (and help a bit if you’re not a fan of jerk-ass little bugs flying around), but the DE + mosquito bits should murder the crap out of them within a couple weeks.

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#44

I just took care of my FN problem the other day by using a sprayer with the flow nozzle opened fully and used a Hydrogen Peroxide mix to drench the top of the soil. The mix was light at 8 ounces Hydrogen Peroxide (the 3% one) to 3 gallons of water. After the soaking of the surface, the entire surface is covered in ground up Oyster Shell. Let that soak us some of the moisture and you can also see them going bananas on the surface. After you’re done being entertained by dying gnats go ahead and give them all a good watering. Mine got a good watering with compost tea, then about an hour or so later a light mixing up of the top loose layer of soil then some water again. Not a lot though, just enough to see the Oyster Shell saturate into the soil more. Couple days later I haven’t seen any. Now i have cats lurking!!

That took care of 7 plants in the ground outside.

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#45

Malted barley and neem meal topdresses. Neem oil sprays. They will be gone fast. Just dont fuck around:)

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#46

has anyone used beneficial nematodes??? i’m going to get some today if the garden centre has them!

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#47

https://www.youtube.com/watch?v=aiebPYJdMcU