Help for fungus gnats

16 years ago

I've seen a few messages about fungus gnats taking out a whole batch of seedlings. While I'm not usually one to drop a lot of chemicals into my plants, in order to maintain the dozen or so plants in my work "cube" I've had to invest in a systemic insecticide. The one I use is safe to use on tomatoes, roses, shrubs, and flowers too. It's made by Ferti-lome and is only about $3.98 for a moderate-sized bottle of the dry granules. Active ingredient is 0-0- Diethyl S-2 (ethylthio) ethyl phosphorodithioate.

A little bit is all it takes to clear up the problem, although management practices (avoiding damp soil) go a long way too!

HERE'S TO A HAPPY/HEALTHY NEW CROP OF SEEDLINGS!!

Kristi

Comments (9)

haweha
16 years ago
Thank you for the info, Kriti!
For and against insects rspectively, I would prefer preparations with the systemic insecticide Imidacloprid.

The common name of the active ingredient you are applying is Disulfoton and it is a systemic thiophosphoric acid ester and its rather hazardous and I wonder that it is at all available for the private gardener.
Ranked as one of the most hazardous compounds (worst 10%) to human health. (see link below)
And, isn't it rather odoriferous?
However, if you have to fight against tarsonemid mites TOO then your advice is certainly very valuable. I use Dimethoate in the combat against those bulb scale mites.

Here is a link that might be useful: Properties of Disulfoton
kaboehm (zone 9a, TX USA)
Original Author
16 years ago
Thanks Hans. I bought this at the local garden center, and use it rarely. I just thought if it came down to losing an entire year's worth of seedlings, it might be worth a little risk! I do know that it has an odor, but it disipates quickly (into the ductwork no doubt)! If handled properly, I don't have a problem with it....and promise I won't taint the office coffee! It's the only way that they let me keep plants at the office! At the first sign of a gnat, each plant gets inspected and treated if necessary.

I'm sure I wouldn't be able to buy it if I still lived in California, but this is Texas...and it's amazing what you can buy! Not necessarily safe, but always for sale!

Thanks again!
Kristi
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mariava7
16 years ago
Sir Hans...Imidacloprid is available here. Most of the preparations are sold/recommended for Roses, trees and shrubs. I think I bought one (Bayer) to use on my Dogwood trees for they seem to get insects/mites during late spring/summer and it's impossible to spray them (taller than my house).

How much of this preparation should I use on my hippeastrums? How often? I think I don't see recommended rates for them in the instructions. Will Imidacloprid take care of mites and narcissus bulb flies?

Mosquito dunks will take care of fungus gnats. And so will the Schultz 3in1. Both being very safe to use indoors.
kaboehm (zone 9a, TX USA)
Original Author
16 years ago
Glad to hear that the 3 in 1 will also take care of gnats. I try to control moisture in the soil as that seems to be one of the main causes. Will use the 3in1 at work, as I really DON'T want to use teratogenic carcinogens around coworkers...really! Thanks for the info!
Kristi
jodik_gw
16 years ago
I have found the best way to eradicate fungus gnats indoors is to use Schultz's 3-in-1 spray directly on the surface of the pots, and to simply kill the flying adults with a flyswatter. Repeated sprays are necessary to kill any hatchlings from the soil.

It also helps to bottom water, keeping the soil surface rather dry. Fungus gnats thrive in a moist environment, and when you don't provide one, they don't stay.
macthayer
16 years ago
I use a very environmentally friendly product that is highly effective against fungus gnats. It is Bacillus thuringiensis (Bti), and is found in a product called "Knock out Gnats". You can find this product at Gardens Alive (www.gardensalive.com). You mix a small amount of the liquid in with water, and just keep watering your plants with it. It won't kill adults, so you may want to put up a couple of those yellow "sticky traps" to catch them. But it does kill off the larvae in the soil so eventually you get them all with no harm to the plant or to people. MacThayer
tommyr_gw Zone 6
16 years ago
Put one quarter of a "mosquito dunk" in your watering can. It contains BT which will kill the larvae in the soil. It works and is safe to use.
kaboehm (zone 9a, TX USA)
Original Author
16 years ago
A coworker had a horrible infestation in his "money tree" and the best thing to catch the adults was a cup of hot cocoa! The poor girl who sat next to him couldn't keep her morning cocoa on her desk without a sheet of paper across the top or she would go to take a sip and find a bunch of gnats floating in it!! :-)

Thanks for all the advise. It made me sad to read so many posts of people losing seedlings to gnats.
Kristi
jodik_gw
16 years ago
I would have liked to use the Mosquito Dunk method of eradicating the gnats, but in order to get one "dunk", you have to buy an entire package... and they're not that cheap!

But the 3-in-1 spray works just as well, and if the top soil in the containers is kept fairly dry, there's no likable environment for the gnats in the first place!