Fungus gnats.... ARGH!!

[Hedgewitch]

Hi everyone. I'm new to the forum and joined because I'm at my wits end trying to eradicate fungus gnats from my indoor plants. I've tried Neem oil (evidently it's only effective if the flies & larvae eat it), drenching with hydrogen peroxide solution, letting the soil dry out, spraying soil with fly spray.....the works. In a few days they're back. I haven't tried Mosquito Bits but to do all my plants it would cost a heap. 8oz are $64 in Australia and I have hundreds to do, some really large. Does anyone have a cost effective way to get rid of them that's actually worked?

 

[Marck]

Greetings, welcome to the Forums.


Besides, B.t.i. (Bacillius thuringiensis ssp. israelensis) there are also nematode controls, and sticky traps to reduce the adult population. I'm not sure what the cost and availability is for these other options in Australia. There are also more toxic pesticides that I don't recommend for this, but they are out there if you are interested.

Removing dead leaves and partially-decomposed plant matter on the soil surface, and applying a rock or pebble mulch to your houseplant containers may also give partial relief. I wouldn't aim for complete elimination here, just population reduction.

Another possibility that is free, except for the labour of moving pots, is summering your houseplants outdoors where the fungus gnats will encounter a variety of predators that won't cost you anything. This option is best done now as Summer begins in the Southern Hemisphere. With hundreds (!) of indoor plants this may not be possible for all of them, so observe and prioritize which are the most needy cases.

 

[Hedgewitch]

Thanks for your help Marck. I'm willing to give the other pesticides a go. I've used malathion before but it's a last resort, not sure it's even on the market now. One of my maranta looked really bad so I got the magnify glass out and went through the roots and soil and found 4 of the little blighters so I don't think I have a bad infestation but I want them gone before it is. Thanks again.

 

[Sheal]

I've recently heard that inserting a number of matches head down into the soil of each pot works. I've not needed to try it though.

 

[Hedgewitch]

Thanks for the tip. Might be something to do with the sulphur in them. I'll do some more research. At the moment I'm spraying the top of the soil with fly spray. I know, I can hear your screams from here. I've chosen the milder type not the surface spray and so far it seems to be working, although over the past two days I have seen a couple flying around but I'll keep on top of it, hopefully without poisoning myself or the plants.