Fungus Gnats

[GoDawgs]

I'm playing indoors with micro cherry tomatoes this winter. These three were started Oct 30 and when I checked yesterday the roots weren't quite to the bottom of the pots yet. They will eventually be transferred to a one gallon pot. Lille Lisa and Red Robin are red and Jochelos is a deep yellow.



There have been fungus gnats out and about on these and the two broccoli plants I have coming along. The plants probably had not been allowed to dry out enough between waterings. My bad. I thought I remembered reading about hydrogen peroxide spray as a treatment so I looked it up. Yep. One part regular 3% peroxide to three parts water so that's what I mixed up and put in a little spritzer bottle. I know it's probably been discussed before but I'm posting this in case there are new folks who have joined who might have missed any previous posts.



Peroxide won't hurt the plants at all. The pot's soil surface and the plants themselves need to be sprayed daily for ten days, as that's the fungus gnat life cycle. By the end of 10 days any eggs in the soil will have hatched with newly hatched gnats having come to the surface to meet their doom. The treatment worked like a charm. They're gone.

There was also one tip on telling the difference between fungus gnats and fruit flies: fungus gnats are slow and easy to grab but fruit flies are a whole lot quicker. Quicker than I am! That's got me wondering if peroxide spray will also work on fruit flies that, from time to time in warmer weather, may invade the small compost bucket I keep by the sink. We'll see.

[Labradors]

Interesting to know!

I read somewhere quite recently that pouring boiling water over the sterilized potting mix will kill any fungus gnat eggs. That could be a handy thing to try if you know you have some infected potting mix! Not only that, but boiling water also makes it absorb the water much faster than cold (except that you have to wait for it to cool down before planting anything).

Linda

[brownrexx]

I put my potting soil / soiless mix outside in the freezing temperature for a couple of days before I use it in the spring and I very rarely see fungus gnats. I use the freezer if it is not cold enough outside.

If I get fungus gnats, I put part of a Mosquito Dunk in my watering can and water with that.

[pepperhead212]

I always put some Bt israelensis in both my soil, and hydroponics setups, to prevent fungus gnats.

[AZGardener]

I also use boiling water with my seed mix and have no issues until the seedlings start going outside to harden off. When the gnats show up, I treat with gnatrol (active ingredient Bt israelensis). I've tried other methods (apple cider vinegar, cinnamon, sand) and have had the best results with boiling water and Bt. HTH

[brownrexx]

Bt israelensis is what Mosquito Dunks and Mosquito Bits are composed of. They kill the larvae not the adults.

[GoDawgs]

Fortunately I've not had fungus gnat problems before but it's good to know about the boiling water and bT Is., etc for infected potting soil mix.

[pepperhead212]

Bt israelensis is what Mosquito Dunks and Mosquito Bits are composed of. They kill the larvae not the adults.

That's where you have to attack them - a preventative measure like that. I do this with my large plants I bring inside, about 2 weeks before bringing them in - one of the major sources of indoor fungus gnats. There are always some larvae in the upper 2" or so of the plants outside, unless treated on a regular basis.

[bower]

I had a plague of fungus gnats on the indoor plants until I discovered Bt-i (mosquito dunks or bits). Yes it is tricky to deal with adults, and perhaps the peroxide is best for that. We tried a combo of yellow sticky traps near the soil for adults along with mosquito dunk in the watering can for the larvae, but it was not a 100% solution in that season. The year after, a pre-emptive strike with the mosquito dunk watering has completely prevented any gnats from emerging. I would do that again for any plan like, growing peppers to maturity in the house. They are such magnets for trouble anyway (aphids!), but the fungus gnats ate their little roots and really caused them a sad time.

[pepperhead212]

Here is the Bt israelensis that I use. It is a liquid, which only takes 8 drops per gallon of water (I use filtered water, since Cl might kill the bacteria), to either moisten the seeding mix I use, or to moisten the pots, before bringing them in. The mosquito dunks I use small pieces of, in my hydroponics, and SUVs. I never see a fungus gnat indoors any more! The liquid stays active for 2 year at room temp, according to the company, but I keep it on the door of my fridge, anyway.

[MissS]

Granular diatomaceous earth placed as a topping on the soil will also control fungus gnats. If you use mycorizae in your soil then avoid using the hydrogen peroxide. It will kill them.

[Nan6b]

The DE helped where everything else failed, for me.

[GoDawgs]

I have food grade DE down in the shed so I can try some of that. The feed 'n weed probably has mosquito dunks this time of year. Everybody else has cleared the garden center and stuffed it with Christmas.

[Amateurinawe]

Same here [mention]GoDawgs[/mention] I went last weekend to the local garden centre and it was full of glitter, trees, christmas lights and I couldn't find half the stuff I wanted. So i got some manure quick and got outta there.

[brownrexx]

I purchase food grade DE at Tractor Supply because people use it in chicken coops. I actually use it there too as it kills bird mites that get into the cracks and crevices of the coop.

[Cole_Robbie]

Skeeter dunks.

[GoDawgs]

I found the skeeter dunks today at my feed & seed. Now, how big a piece of the dunk to how much water? I just need to make up about a pint of it.

[pepperhead212]

[mention]GoDawgs[/mention] With that, you'd probably have better success with grinding it up, and mixing it in the upper 2" or so of soil in a pot (or, all of the soil mix, if starting a pot, or seed starting pots. It doesn't take much - they sell similar items for a lot more than the dunks, when you figure out cost per ounce, and they don't call for much. I remember many years ago the company that I originally got the liquid Bt is. from switched to the granular, and it was only about 4 oz, for almost $20 (supposedly made 100 gal, to water with), so I found the liquid elsewhere. But the dunks would work fine.

[AZGardener]

I just wanted to add that using skeeter dunks or any of the other Bt products kills the larvae, not the adults, eggs, or pupa.
So, it may take 2 or 3 doses to get rid of them. But it works better than anything else I've tried, and I think I've tried
about all of the methods google searches can bring up.

[brownrexx]

A whole dunk controls hundreds of gallons of water so I just crumble a small amount into my watering can. Lots of solids will fall to the bottom but those are probably just fillers.