Battle of the Fungus Gnats

[lakelady]

I have some mosquito dunks in the shed, that's an idea.

Cole Robbie, I have arachnophobia lol

[cythaenopsis]

Thanks so much for this post. I don't have a fungus gnat infestation... YET! But I have an orchid that was suffering from it. In fear of contaminating my other orchids, I put the pot outside for a bit before deciding what to do with the plant (save or toss it). It was right nearby my tomato plants. Uh oh... Moist soil. Mulch on top of it. Hmmmm... yeah, now that I think of it a fungus gnat would be in paradise there. So I bagged up the plant and took it away. If it weren't for this topic, I'd never have known.

Sure enough I did find a couple of stragglers parked on the side of the tomato containers. Nailed them. But who knows if some went exploring around out of sight. I'll have to keep my eyes peeled. In any case, I'll definitely keep this remedy in mind if it looks like an infestation is trying to take hold. Thank you, Carolyn!

[cythaenopsis]

Well, I found myself with a major fungus gnat infestation...

Apparently they're small enough to climb through the holes of window screens. I was getting more coming in than made sense to me, so I rustled up the mulch layers on my tomato plants--dozens of the little buggers flew up.

I know they're pretty much harmless to the tomato plants, but I don't like the idea of them coming into my home and flitting about anywhere they please (I had a couple buzz in front of my face when I was reading in bed!).

I'm going to set some traps for them, using vinegar in tall containers. I also added a peppermint Castillo soap to some water and doused the mulch covering with it... the peppermint won't harm the plants but the gnats seem to hate the stuff. Anybody here ever tried it or have other suggestions on what to apply?

[stromato]

For years a well-meaning relative has brought a potted plant for the holidays. Invariably, those plants, from many different nurseries, have had gnats which quickly colonized all the other plants.

After many years of trying everything, we found that only repeat applications of a BTi drench to every container really worked; that is, there would no longer be even one gnat flying in front of anyone while reading in the evening—which I believe is the standard test for whether gnats have been properly controlled. (Repeat drenches of BTi are, of course, required since it is only effective on one developmental stage.)

Or, if you dare, you could just nuke ‘em, as Raybo suggested. I’ve never tried that but it would likely be very effective and probably with fewer applications than are necessary with BTi.

[Labradors2]

I often get infestations of fungus gnats in my houseplants. The best way that I have found to control the problem is to let the soil dry out in between waterings, and to water only from the bottom. I have tried sprinkled powdered cinnamon of the surface of the soil and that helps, but is not enough to control the problem. I think that adding sand to the top layer would be good too, but I never remember to pick up some sand when I visit the beach!

HTH,
Linda

[cythaenopsis]

Thanks for the tip on the BTi, stromato. Looks like Gnatrol has it, based on earlier postings. Also, mosquito dunks contain it. I guess you could crush up a dunk, mix it with water, and then use it for drenching.

Incidentally, I'd never heard of BTi before. I looked it up and it's a bacterial agent as opposed to chemical.

[Labradors2]

Originally Posted by cythaenopsis

Thanks for the tip on the BTi, stromato. Looks like Gnatrol has it, based on earlier postings. Also, mosquito dunks contain it. I guess you could crush up a dunk, mix it with water, and then use it for drenching.

Incidentally, I'd never heard of BTi before. I looked it up and it's a bacterial agent as opposed to chemical.

I've used it on roses and on red currant leaves before the plants fruited BUT it smells DISGUSTING and I don't think I'd want any of it to land on my tomatoes!

Linda

[ArthurDent004]

I had a major infestation myself around my indoor strawberry plants. I first tried the same apple cider vinegar traps I used to rid myself of a fruit fly infestation last year. I set out three traps and after one week I had caught less than 10 gnats total. I came across the sticky yellow squares but I couldn't find any locally then I saw this at my local Wal-Mart - a four pack of Raid Fly Ribbon - http://www.amazon.com/FR3-RAID-Count..._sim_sbs_hi_12

I used all four - one dangling down to the soil of my first strawberry plant, one by the window near the plants, one hanging from a floor lamp near the door of the room the plants are in and one hanging by my patio door. These strips outperformed my wildest expectations. Within a week the ribbon by my plant was covered with gnats. I keep looking at articles for gnat control and came across Bacillus thuringiensis. I started looking for products that contained this. It also happened that I was looking for a product containing Mycorrhiza because I wanted to see if it lived up to the reviews I'd read. I found that Myco Madness - http://www.plantlightinghydroponics....oz-p-2638.html contained both products. I started adding it to the feed water for my plants and have been most happy with the results. The fly ribbon catches the adult gnats and the Myco Madness seeds the soil with the bacteria that kills the baby gnats.

The mycorrhizal fungi colonized the plant roots and extends the root system into the surrounding media, greatly enhancing the absorptive surface area of root systems.

[stromato]

Cythaenopsis, while you are waiting for your Gnatrol to arrive, rather than dunks, you would get more bang for your buck with Mosquito Bits, made by the same manufacturer. They are both usually sold at big box and some hardware stores.

Last time I checked, the Bits are just bits of corn coated with vegetable oil to which the BTi adheres. You can make a wonderful tea for the gnats by soaking about a quarter cup of bits in some form of tea bag in one or two gallons of water for fifteen minutes.

If you already have dunks, you could soak one in your watering container—no need to crush it—but results with dunks seem to be less reliable, perhaps because the concentration of BTi is lower.

[David52]

Before I started using the granules/mosquito bits, I used to fill a 2 gallon bucket with tap water, let that sit for 24 hours to allow any chlorine to gas-off, then tossed in 1 or two of the doughnut dunks, let that sit for 24 hours, then used the water on the plants.

But these days, sprinkling a few teaspoons of granules around any and all container plants, usually once a year, does the trick.

[cythaenopsis]

ArthurDent, thanks for the tip on the Raid fly strips. I'll definitely pick up some.

Stromato and David, those mosquito bits/granules sound like an effective treatment. Thanks!

[cythaenopsis]

I ended up buying Mosquito Bits (seems to be just one brand that makes this, hence the rather hefty cost) and applying it. Hopefully it'll help eradicate the fungus gnats. I sprinkled it liberally over the mulch and I'm top watering for the next week. I had to apply it to my herb pots as well, as the gnats were thriving in the chive forest--apparently an ideal kind of environment.

I also ended up with some house plants affected, because the young gnats are small enough to pass through screens.


BTW, a useful tip: In the evening after your last use of the bathroom sink prior to bedtime, fill the sink up about an inch with water, mix in a few spritzes of fragrant hand soap that lathers well (I'm using Nature's Gate Organics Lemongrass & Clary Sage liquid hand soap--you can pick it up at Walgreens.com for $7), then fill the sink about half-way being sure to let a soap foam layer build up. Depending upon the degree of the infestation, you may find in the morning a decent cluster of dead gnats. They are drawn to the smell the soap, land on the foam, and then the soap ruins their ability to fly causing them to drown. Very cheap and effective way to at least kill a good number of them, because the gnats can fly from one end of an apartment to another in just a minute or two (fast and strong little buggers).

The thing about this Nature's Gate hand soap is that the foam persists for a long time, which means it can catch gnats for a good stretch. If you use a soap where the foam dissolves quickly, it may not work well. Also, I have to wonder if the lemongrass and/or sage is particularly attractive to the gnats. You might get less impressive results from other fragrances. In any case, the soap is quite pleasant--and added bonus.

[cythaenopsis]

The mosquito bits are working, thankfully. It took almost 2 days, but in the pooled water I now see a graveyard of fungus gnats. There are still a number of them flying around, but I suspect they're younger gnats that haven't eaten the bits as of yet (I'm hoping they're not resistant!). The stuff diluted in the water also seems to affect the gnats. I spied one flying low over the water and then it seemed to struggle to get up over the tray edge, eventually falling back into the water and flailing. I take no joy in seeing something suffer so I snuffed it out. These gnats are fascinating creatures that are well adapted for what they do... but their quickly growing population makes them a menace.

The directions say to sprinkle liberally, covering the entire surface. I'm not so sure such a dense layer is needed. But I understand why they recommend it--it's self serving, as you run out faster and then you have to buy more.

[stromato]

The bits only kill the larvae in the soil, so your adult (flying) gnats must be dying for some other reason.

[cythaenopsis]

^ The directions say that the gnat larve ingest the contents of the bits that have seeped into the soil and this kills them. Since the larvae are attracted to eat it, I'd think that the adult gnats would as well. I had placed the bits in a pool of water around the plants which made a kind of amber broth. No doubt since the gnats are attracted to moisture, they probably ingested the brew. It's the only thing I can think of.