Knock Out Gnats.....Anyone used it with Success?

artzypantz(z5 / IOWA)April 20, 2007

I have Gnats in my potting soil again this spring.....this is the second spring i have encountered this problem with my indoor house plants and seedlings. I repotted everything last fall to try to keep from having this problem, but to no success. I didn't notice them during the winter, (but hardly watering in winter and maybe i just didn't notice them) so i don't know if they came in with the new bag of potting soil this spring, or if they were there all winter. I have also had really big problem with getting potting soil that smells moldy when i buy it,(2 different stores even) and it seems the wood chips in it mold as soon as water touches it!

(Miracle Grow is no longer going to be my choice for house plant potting as its making us all sick, plants and people! I don't know if this bad smelling soil is bringing the Gnats with it or what, but it smells horrible to say the least. I am not sure if its what they are putting in the soil contents or if this problem is due to the way the store is putting the soil in storage)

Any how, i have tried repotting as i said, with no luck, i also tried watering with a bit of vinegar in my water which wiped out a few of my plants and left the gnats. Now i plan to purchase this stuff online called "Knock Out Gnats", which is $20.00 for the stuff.

Have any one here used this with success?? I don't have $20.00 extra as a single mom, and if its not going to work i'd rather have someone tell me now then find out the hard way!

Thanks.......& if you have any other product suggestions that are successful i sure would appreciate it! Plants help to brighten our days and our home, i hate to lose that to these stupid creepy gnats!

Enjoy your day!


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Gnats will only appear if the soil conditions are right for the eggs to hatch and the larva to grow into adults, and that happens when the soil is kept too moist. No expensive controls are needed just monitor watering better and do not water those plants until the soil says it needs water. Check that need by inserting your index finger into the potting soil to the first knuckle and if the soil is dry that deep water and if it is not don't water.

    Bookmark   April 20, 2007 at 7:34AM
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morz8(Washington Coast Z8b)

Tonia, yes - the Knock Out Gnats works very reliably. Any of the products with BTi (baccillus thuringiensis subspeciies israelensis) will take care of gnats.

Don't become impatient with it though, it takes about three consecutive waterings (on your normal watering schedule) with the BTi solution to stop the breeding cycle and elminate them. I don't water until houseplants begin to show a little wilt, like every 7 - 10 days, so that means about 30 days before they are truly gone.

    Bookmark   April 20, 2007 at 11:10AM
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ken_adrian Adrian MI cold Z5

next year.. try the suggestions at the link ....

do it yourself.. even if the bag says it was done in advance ...


Here is a link that might be useful: good luck

    Bookmark   April 20, 2007 at 12:46PM
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rhizo_1 (North AL) zone 7

Tonia, I'm interested in what you've said about your potting soil. Are you using the MiracleGro GARDEN soil or their peat based potting medium for container plants? I'm asking because several people have commented on using the soil by mistake, commenting on the smell, bad texture, etc. I also don't think that the container mix contains bark, but the garden soil does.

Though the majority of MiracleGro potting medium users seem to find fault with it at some time or another, not too many people remark about a horrible smell. So....I'm just wondering.

Good luck with the Knock really does work great!

    Bookmark   April 20, 2007 at 1:07PM
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artzypantz(z5 / IOWA)

Good morning all! Thank you for your replies!
I am so glad to hear the Knock out Gnats will work, i will go ahead and purchase it today!
I used to make my own potting soil with black dirt, sand, & perilite, but then others said it wasn't good for houseplants because there was no nutrients in the soil and it was to heavy when drying out which kept oxygen from reaching the roots. I did have more problems with other pests when using my homemade soil, but not gnats. I may go back to experimenting with making my own again.

The potting medium i have been using says on the bag......
Miracle Grow Potting Mix for indoor/outdoor containers.
This stuff has actual wood chips/chunks in it. I bought some last season and also this spring, both with the same very bad smelling, moldy mildewy smell. Actually strong enough to make you cough when breathing in above an open bag or a pot of wet soil. I also noted that when starting seeds in this mix, after the top had been wetted, in 2 days the wood chips showing on top of the mix, started to grow white mold and the smell was worse. The wood in it looks like some of the shreded mulch you see for sale.

My concern with trying to sterilize potting medium is whats in it. Are we talking sterilizing actual soil and not the peat based mixes?
Most container mixes have fertilizer, perilite, vermiculite, & wood chips in it, which causes my concern of heating this up in the house. Especially me, as i am the worlds worst cook to begin with! Any thing concerning the stove/oven and me,is great cause for concern and disaster! ;)
Thanks for helping me learn & grow with my plants!

    Bookmark   April 21, 2007 at 11:30AM
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rhizo_1 (North AL) zone 7

You can make a pretty good container mix out of plain peat moss and perlite...mixed at about 50:50. Not fancy, no other amendments, NO SAND, NO BLACK SOIL. Initially, it will be hard to get moistened, but with a little mixing, it will do the job better than the typical packaged potting medium. And the fungus gnats are not likely to be at home when there is so much perlite in the mix! Fast drainage of water and lots of nice big pore spaces will result in happy, care-free plants.

Ken is the only one around here who sterilizes his potting mix, so he will have to speak to all of the FUMES issues, lol! Yikes! Never in my house, I promise you that!

    Bookmark   April 21, 2007 at 1:00PM
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artzypantz(z5 / IOWA)

Hi rhizo_1! Thank you for the recipe! I will do that!
I noticed the potting medium was hard to get wet also. Whats the problem with Peat? At times it seems it refuses to soak up any water at all! About 10 years ago miracle grow had a good mix and i never had any real problems with pots. Now theres barely any perilite in the mix. I used to use the cactus mix for every thing but it was to much money for the tiny amount you get.
We should develope and market a new brand lol (just kidding)!
Thanks again & enjoy your day!

    Bookmark   April 24, 2007 at 10:02AM
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I purchased the Knock Out Gnats, but the mixing instructions are not helpful. 3.2 - 6.4 oz/100 gallons???
How about the amount needed for 1 gallon??? This is a house plant infestation and not a ranch/farm infestation.
Any advice apopreciated.

    Bookmark   June 1, 2011 at 1:06AM
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