Fungus Gnats 2022
 

I’ve searched the forum, but any updates on how to treat fungus gnats in 2022? Brought them home in some orchids in moss and now I’m having problems in many of my orchids, especially those with a bit of moss at the top mixed into bark. I know people suggest mosquito bits but I have not found success with them, nor with hydrogen peroxide.

I read about imidalacropid (sp) working to eliminate the larvae and wondering if anyone has thoughts on that. I have used it in the past with a liquid I mix and pour through (did this for mealybugs) but I recently bought another product that stays on top—systemic granules from bonide. I don’t really like using these so far as feel I’m encountering much more pesticide and they have a bad odor.

Thoughts on the latest in the war on fungus gnats? Thanks all

I prefer using mosquito dunks...
I posted how I use them in a different thread, a quick search of the forum for Mosquito Dunks will help you find that thread quickly.

They do not work to eradicate an infestation quickly, but your infestation will decline over a few weeks until they are all gone.

I am also a fan of the dunks. For my regular houseplants all I do is let them dry out a bit more than normal and water from the bottom for a few weeks so the top stays dry and discourages the adults from laying eggs. For things that can’t dry out, use dunks.

Train a fan on the plants. They're too weak to fly against it. As adults hatch out and blow away they're unable to lay more eggs. Before long they're gone.

I just use Gnatrol every 3 days if I get an outbreak of them. It's a powder dissolved in water, so I just use during watering. It's Bacillus thuringiensis subspecies israelensis, so just a variation of the mosquito Bt. It only lasts 3 days and only kills the larvae so you have to use it a few times to kill everything off. But it does seem to work fine.

Gnatrol and Mosquito Dunks/Bits all contain the same bacterium.

Insufficient results using them could be due to using chlorinated water, not soaking the dunks long enough, or by not applying enough of the “contaminated” water.

When I had a gnat problem indoors here, I kept several 2.5-gallon jugs of dechlorinated water, each containing a “Dunk”. I water from one, then refill it. The next watering comes from another jug. That way, they get several days of soak time to develop the bacteria population. I continued using only that water for about a month, as the gnats have a 2-4 week life cycle.

What has worked well for me is to repot the orchid with just bark and no sphagnum moss and to use yellow sticky traps. Sticky traps are good as preventive measure but not for treating heavy infestations though. For heavy infestations I just repot and reintroduce sphagnum moss once the gnats are gone.

Pinguicula

Easy to grow and attractive once they consume all the gnats.

Dealt with a bad fungus gnat infestation in late 2020 probably from a bag of Miracle Grow orchid mix. Tried yellow sticky traps, mosquito dunks, and beneficial nematodes without success.

Ultimately had to repot all my orchids in a different mix which I made sure did not have peat moss listed as an ingredient (which I suspect the gnats like). Haven't had any issues since :goodluck: