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So... what are these things eating my roots?

Posted by karenrei 4b/5a Iowa City (My Page) on
Tue, Jun 2, 09 at 15:00

I have some plants indoors whose soil has been infested with some sort of insect. The first pot that was infested, shiso, has become dwarfed and not grown one bit since the infestation. The second pot that has become infested is my prize LED-grown pepper that had just started flowering, and now it's starting to lose its lower leaves. My first thought was, obviously, everyone's main target: fungus gnats. However, I've come to doubt this hypothesis.

1) The little white creatures that I see occasionally on the soil surface (never on the plants themselves) are clearly not wormy, which fungus gnat larvae are. They actually walk across the surface in a rather fast, legged manner (although they're too small to actually make out legs).

2) I've been treating my soil with BTi for a week and a half now, and I have nothing to show for it.

Sorry, no pictures -- they're too small, and duck out of sight too often. I tried an insecticidal soap coating on the top of the soil in case they're soft-bodied types that the soap can kill and in case they don't go deep enough into the pot. But if that doesn't do the trick, I'm thinking I'll have to up the ante and go with a pyrethrin soak.

Thoughts?


Follow-Up Postings:

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RE: So... what are these things eating my roots?

Bt-i is only effective for larvae of certain members of the fly family, like fungus gnats. Don't waste your money if that's not what you have.

Why not try horticultural diatomaceous earth?


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RE: So... what are these things eating my roots?

I have some diatomaceous earth, but my experience is that it gets washed up by watering. Also, using the stuff indoors doesn't sound pleasant, from a respiratory standpoint.

Bt-i is only effective for larvae of certain members of the fly family, like fungus gnats.

Hence, the fact that it didn't work helped convince me that my fungus gnat hypothesis was wrong and to take a closer look at the critters ;)

I pyrethrined last night. I also managed to smash one of the adults to get a closer look at it. Pale, almost translucent yellowish body, translucent white wings, total size about 1-2mm. Didn't look like a whitefly, though, and the soil isn't whitefly habitat anyway.


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RE: So... what are these things eating my roots?

Have you thought about using nematodes?

http://gardeningzone.com/index.php?cPath=25_75

that is where I ordered Steinerema feltiae... I'll let you know in a few days if my assorted fly problem has gotten better =P


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RE: So... what are these things eating my roots?

You wrote "...the fact that it didn't work helped convince me that my fungus gnat hypothesis was wrong..." (and that after 1 1/2 weeks)

As it turns out, one must use Bti with every watering for at least 3 weeks to disrupt the gnat's life cycle.


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RE: So... what are these things eating my roots?

I considered nematodes, but they're just so expensive. Plus, once they finished up the insects that were infesting my soil, they'd starve, as this is an indoor setup, not outdoor.


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