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Old 16-11-2006, 03:41 AM posted to rec.gardens
Father Haskell Father Haskell is offline
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First recorded activity by GardenBanter: Sep 2006
Posts: 142
Default Fungus Gnats and Pyrethrum


Just Asking wrote:
I have a few questions:

1) Can you kill fungus gnat larvae by drenching the soil with a pyrethrum based solution?


Yes. Also, permethrin family insecticides, synthetic pyrethrins fine
tuned
for better kill and longer persistance.

2) Can you kill fungus gnat larvae with hydrogen peroxide (h2o2)? Will this kill the plants? If not,
what is the best strength?


I've used 3 percent drugstore peroxide cut to 1/2 percent without
causing
noticeable harm. Kills the gnat larvae indirectly, by killing the
fungus
that turns healthy root hairs into gnat food.

Tried cultural fixes? Try root pruning and repotting in clean soil.
Then
cut back on water. Drowned (and dead) roots is what draws gnats.
Near-terminal cases may require taking and rooting cuttings and hoping
the fungus infestation hasn't become systemic.

Have you done a potato test to get a positive on fungus gnat larvae?
I wonder if it would be possible to use spud slices as bait to draw
the little buggers to your dose of pyrethrin or BtI, allowing more
kills with less poison?