Fungus Gnats

Kelly O'Neill
Wed, 30 Mar 2011 20:09:55 PDT
> ...Gnatrol,
> but it sounds the same as Mary Sue's
> product.  To clarify, BT is Bacillus
> thuringiensis var. israelensis. ...

I agree the gnat larva can be a real problem and don't go away over time if the 
conditions suit them. I think most peat based soils come with them already living 
in them. Especially if the soil was in bags and sat around in storage anywhere for 
a while. 
   I believe BT is a great solution. I know B. t. i. is recommended. Gnatrol may be 
the best. Instead I used a product called Thuricide which contained B. t. k. 
(where the k is something like kuraski) as it was more readily available to me. I 
think it works very well. It is not quick, so the H2O2 type ideas might be a good 
way to knock down a serious existing problem. A few days later, I'd start the BT 
   My unresearched approach:  I think of the BT as a living critter that I need to 
get growing in the soil. Once I drench the soil it takes time for the BT to multiply 
until my soil is basically immune to the Gnats. Adult flies may continue to be 
present in small amounts but if they lay eggs, they are feeding the BT in the soil. 
If I have any unused moist soil sitting around, I give it a shot of the BT drench so 
the BT can start growing in the soil. I, of course, hit new plantings with some 
also. I try not to kill the BT with harsh chemicals or severe drought. In the always 
pretty warm conditions the Gnats thrive in, this seems to work well for me. 
   BTW, I have not really noticed the Gnats to be a problem in 
unheated/unprotected outdoor containers in Western Oregon. Differences in 
nighttime/soil temperatures or other factors may be what is causing a difference 
of opinion on this list about how much of a problem the Gnats are.

 Kelly O'Neill and 
   Big Bubble Magic(tm) at
and  Wet Rock Gardens Flower Farm
2877 N 19th Street - Springfield, Oregon 97477
U-Pick and more at the farm (open 9 to 6, Sun, 
Wed and Fri - from March thru Halloween) -

More information about the pbs mailing list