Comments on: Fungus Gnats

By: Heyokah

Heyokah — Mon, 31 May 2010 04:06:56 +0000

I recently bought a basil plant and got fungus gnats (and some nasty fungus) as well. After doing a bit of research, I found that most ways of dealing with them involve changing the pH of the soil to kill the fungus (and thereby the gnats). Spraying with vinegar (in solution possibly), sprinkling coffee grounds on the soil, etc. Limiting the amount of water to the pot would also help as what you essentially need to do is change the environment that the plants are in – houseplant conditions (constant temp – warm, wet, and not terribly sunny) are great for growing fungus.

I used a route suggested by orchid growers. Sprinkle cinnamon on the soil before your next watering – apparently the cinnamon is toxic to fungus but not to the plants. Worked for me and I haven’t had any problems since!

I’ve also noted a salt-and-pepper jumping spider on the window screen next to my plants. I love those little guys and I hope he’s finding enough to eat but I’m glad my pests are gone!

By: Elizabeth @ The Natural Capital

Elizabeth @ The Natural Capital — Wed, 03 Feb 2010 19:09:24 +0000

This is why I love your blog — you can take a tiny, insignificant household pest and make it interesting.

During the summer we also have good luck getting rid of fungus gnats by just putting the potted plants outside for a while — not really an option when it’s below freezing outside. I’m not sure why it works — maybe the heat just dries out the soil faster. In the winter it’s easy to overwater since a) our house is chilly, leading to less evaporation and b) plants are less active due to shorter days. Letting the soil dry out between waterings usually keeps these guys in check.

By: Andy Kaiser

Andy Kaiser — Mon, 01 Feb 2010 02:53:36 +0000

Thanks for the confirmation.

They were really annoying – I’m interested in buggy things, but I get almost phobic when they’re flying free anywhere near where I eat or sleep, and at the time I kept my orchids in my kitchen.

However, I did have a way of getting rid of them – I don’t know if this actually killed them, or (perhaps more likely?) killed their food supply, but what I did when I noticed them was to:

1) Completely fill/drain the orchid pot (I’d do this and the following steps with the orchid still in the pot).
2) Dump a bunch of orchid fertilizer directly on the orchid potting material (totaling 1-2 tablespoons’ worth).
3) Fill up the pot with water, and make sure all the fertilizer was dissolved. Mix it up good.
4) Let it drain out as normal.

…then, when it got dry again (every 4-6 days), I’d just water the orchid as normal. For me, after doing that process once (or sometimes twice), the gnats would be gone for at least a couple months. Worked really well, though I do NOT recommend my technique for anyone reading this – that amount of orchid food should be lethal to the plant itself (though my orchids did pretty well. Go figure.)

By: Tim Eisele

Tim Eisele — Mon, 01 Feb 2010 02:08:11 +0000

Yes, they are pretty good at hovering, and do tend to fly quite slowly. The University of Florida site says " There is not a similar insect in the production area or interiorscape", which I take to mean that any time you have tiny flies that are breeding in flowerpot soil, they almost certainly are these. So, I expect that you did, in fact, have fungus gnats. Actually, I kind of suspect that practically everybody who keeps houseplants has at least a few fungus gnats.

By: Andy Kaiser

Andy Kaiser — Sun, 31 Jan 2010 14:42:58 +0000

Tim, in order to compare and ID these in my own house, I’m wondering about their method of flight: are these gnats really good at hovering and flying really slowly? I used to have a lot of such things when I had orchids, and noticed they were always worse when I overwatered.

Andy

By: K T Cat

K T Cat — Sat, 30 Jan 2010 23:46:39 +0000

One of the best things I’ve learned from your blog and something I’ve regaled my friends with is how many insects have other living things do most of their digestion for them. This is another great example. The digestive tract of this little guy must be just a few hundred cells long.