Soil Mites That Eat Fungus Gnat Larvæ

[My Green Pets]

So far (fingers crossed), I haven't had any pests or diseases to attack my plants. Except those blasted fungus gnats. They are everywhere. At this point, I can't sit for more than a few minutes, anywhere in the house, before a gnat comes buzzing my way.

Now, whenever I buy a new plant, I have just accepted that it, too, will eventually be crawling with them. But maybe, just maybe, that won't be the case for my latest addition.

I got a new plant this week and, a few days later, saw a couple of tiny, white, spider-looking things in the medium.


Photo from Buglogical Control Systems

"Great," I thought, "I just got this thing and now I have to deal with a mite infestation."

But a quick search online soon revealed Hypoaspis Miles, a beneficial soil mite that preys on fungus gnat larvæ. They are actually available for purchase as a beneficial bug! Perhaps the nursery where my plant was grown uses this mite to control their gnat population.

If my new plant stays gnat-free, I'll feel a bit more sure about what these little guys are. I may end up a little regretful for smashing one of them earlier!

[Ray]

I wish you luck with that, but let me throw out something else to consider:

The presence of a fungus gnat population is the "canary in the coal mine" warning you of decomposing potting media that supports fungal growth. Controlling the larvae or trapping the adults may treat the symptom, but does nothing to address the underlying problem.

[S&K Maley]

I agree with Ray but one thing we have done till time to repot is crumble some BTI into the pot and no more fungus gnats.

[My Green Pets]

S&K Thanks for the advice, what is BTI? —Edit, I just looked this up. Looks amazing...now where to find this in France?

Ray thank you, the orchids (except the new one) were all repotted within in past few months (and in fairly course mixes at that)... There are other houseplants including an areca palm, a dracæna, a ficus...repotting these guys is out of the question at the moment as 1) it is winter and 2) they are enormous (the dracæna alone is 9 feet tall).

Biological warfare might be my only recourse...

[S&K Maley]

BTI is sold as mosquito dunks. Repotme sells them but we buy them at big box stores.BTI is a soil bacteria which when ingested by the gnat larvae does them in.We also crumble some into our humidity trays and all orchids in S/H get it once a month.We highly recommend it as it is non toxic to anything other than mosquitoes and fungus gnats.

[My Green Pets]

Well I just bought some BT online, we'll see how it works! Thanks for the recommendation!

[My Green Pets]

Well it turns out I have bought the wrong stuff.

I saw Bacillus thuringiensis and thought I had the right stuff.

It was only after ordering did I discover that there are many different strains of this bacteria, and each one is only effective for certain pests.

The one I bought was Bacillus thuringiensis kurstaki which, according to what I'm reading, is only good for killing caterpillars

So I've ordered some effervescent tablets of Bacillus thuringiensis serovar israelensis and hopefully this will be what I need.

Feeling dumb right now!

[Harvy Howard]

Fungus gnats can be a problem, especially if you grow a variety of plants in addition to orchids. I have an indoor-light setup, and grow an eclectic mix of plants -- including some African violets that prefer an organic soil that is not allowed to dry out too much. I am now avoiding the use of bone-meal in my soil mixes, and switching over to more vermiculite/perlite materials and less soil/peat-moss.

Anyway, as a non-chemical control for fungus gnats I use the trap method. This is simply a glass jar or large drinking glass containing a bit of banana, the top sealed with clear food-wrap punctured with a small hole big enough to let the flying critters in. I find that apple peelings do the job too, and I add a splash of beer for good measure. During the winter months of below freezing weather I simply let the captives fly off outdoors, and seal the top for the next batch.

Once the number of fungus gnats is at an acceptable low, I move the traps further away from the plants to avoid problems associated with the ethylene gas that is emitted from the ripe fruit. Good growing.

HH

[Leafmite]

My orchids aren't the problem as lava rock or fresh sphagnum moss doesn't really succeed in growing gnats. Some of my other plants, however, were created to be gnat breeding grounds. I go the butterwort route. I might also try a sundew this upcoming summer.

[weederwoman]

I've used BTI, but I also have insect-eating plants. My sundews and butterworts trap gnats with sticky secretions. I also have a lot of nepenthes and sarracenia, but I can't swear these trap anything as small as a fungus gnat. I have never battled a serious infestation, however, but the plants are fun regardless.