fungus gnats and seed starting

Kenneth Hixson
Wed, 09 Nov 2005 11:29:02 PST
	I can't offer a perfect answer to your problem with fungus gnats-
what works one time may not work under other conditions, but here
is what has worked for me.
	Fungus gnats need access to organic matter to lay their eggs.
Cover the surface of your potting mix with something inorganic.  Granite
grit will work, so will perlite, vermiculite, etc.  Each has advantages and
disadvantages, choose what works under your conditions.

	The hose from a vacuum cleaner, held just above the leaves of
seedlings, can suck up a lot of adults.  You can "herd" gnats to the
vacuum cleaner hose by moving your hand over the seedlings toward
the vacuum cleaner hose.  It will take two or three days to get most
of the adults, but it is time well spent.  You can very easily vacuum
up the leaves of your seedlings, so have a helper hold the hose, or
tape it in place for a while.

	For the larvae in the potting media, I simply applied liquid soap,
diluted as directed, as a drench to the top of the pots.  Safer's Insecticidal
soap works, probably so will others, though some soaps may have plant
toxicity.  Experiment on a few pots before treating everything.

	For what it is worth, all soil is composed of broken down rock bits--
with organic matter added.  The actual mineral part of a plant is very small--
a couple pounds per hundred pounds of dry plant matter.  If you've ever
burned wood in a woodstove, consider the amount of ash left after burning
a ton of firewood.


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