Fungus Gnats or Springtails- HELP

[Bill U.]

Hi everyone,

As of last night, I was doing a quick final check over my orchids before bed and in one of them, I have discovered very small, gray/black larva floating in my humidifier tray of my 1 phal. I took that tray, cleaned it out, sanitized it, and then put a tiney bit of water back in it as of 12am and now, 8am, there are MORE (but not nearly as many, yet)!

After looking at them, it seems that they are either springtails or fungus gnats. I am not sure if they are springtails because in that phal, i repotted this past spring (Spring '12). I believe that they might be starting to eat at the roots because my phal's bottom 2 leaves are starting to yellow

I have seen that there are a couple different ways to kill both pests, and that one of them is with diluted hydrogen peroxide watering- does this work?

PLEASE HELP! PICTURES TO COME SOON!

P.S. I know that if they are springtails, then they aren't harmful to the plant, but I would prefer to squash them now before they travel to my other phals!

[NatalieS]

Springtails are very, very, tiny - probably about 1-3mm. As you say, they are not actually harmful. They can be an indication that your potting medium is breaking down, so if you haven't already checked the roots of your plant then I would do that. You might just need to re-pot.

Fungus gnats are more of an issue. The adults are technically harmless but they lay eggs in the damp media and the larvae eat roots and burrow into the stems. Very, very bad! Don't panic though, do you see any tiny black flies hovering around your plant? If not, then what you are seeing is probably not fungus gnat larvae. If you do see little flies, then it could be. I had a real problem with fungus gnats this summer and tried a number of home-made recipes to no avail. 'Gnat-off' and yellow sticky paper has worked. If you can't find any products specifically aimed at getting rid of fungus gnats, then take your plant out the pot, get rid of as much of the old media as possible and rinse the roots really well. Then re-pot into fresh media and let it dry completely in between watering. Fungus gnats thrive in a continuously moist environment, so if you let the media dry out it will discourage them. I don't know about using peroxide - perhaps someone else has some experience with it?

Really, the easiest thing to do as a first step (and if you're really worried) would be to re-pot into fresh media.

[Bill U.]

I'm going to check out the roots and everything later tonight.

I have attached pictures to try and clarify what I am seeing- I know that they are really small, but I couldn't get a closer shot that was in focus. The only places I have been seeing them are in the water under my phal- when I disturb the medium, I don't see anything trying to jump or any black flies starting to buzz around either.

P.S. the one "blight" spot on the one leaf in the first photo was there when it was given to me as a rescue.

[WhiteRabbit]

I suspect fungus gnat larvae. Soaking the pot in some soapy water (dish soap, can also add some rubbing alcohol) for 15 minutes or so should kill them.

[Bill U.]

I took it out of the pot and looked at the roots tonight--> almost all of my roots were rotted away, so now I have little 1/2" to 1" long roots when before it had several inch long roots.

I also dumped the sphag moss (had broken down to the point of being rather soil-y) that I had it potted in out onto a white sheet of paper and there were white/gray tiny little bugs crawling around (nothing that was flying, or jumping).

So I took the pot and washed it out with dish soap and hot water, then washed the roots, applied cinnamon where I cut the roots, and repotted in fresh sphag. I'm hoping that this will solve the problem!

[NatalieS]

I'm sure your plant will be much happier in the fresh media! Just be careful not to over-water while the plant is recovering - it's best to let it dry out in between watering. I find that spraying or misting the surface of the media encourages new roots to grow quickly.

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[wiyosaya]

I had a similar problem with my "ordinary" house plants. I reduced the water that I was giving the plants, and also I treated the gnat infection with beneficial nematodes - Steinernema feltiae

The nematodes significantly reduced the population of gnats, and not watering the plants as much helped, too. It seems that the gnats require more moisture than the plants require.

HTH