Hello:
I had a similar problem a few years ago: it was caused by three things,
seperately, and at different times.
1) The VFTs were being grown in a mixture of milled peat moss and perlite
with a top dressing of live sphagnum moss. Aphids had managed to colonize
the crown of the plants below the top of the vigorously growing sphagnum
and could not be found until I lifted the plant for inspection. Also, these
appeared to be common green aphids, but they were remarkably small; yet
they gave birth to live young (pinhead size) as observed under a magnifying
glass.
2) Same growth medium as above, but some nasty little mite was infesting
the very _inside_ of the crown. I could just make them out with a 5X loupe.
These two I treated with a mild spray of a nicotine infusion with a drop of
liquid dish soap added to ensure contact. The bare-root plants were washed
in rainwater after fifteen minutes and repotted in new medium. All plants
recovered.
3) Two closely growing VFTs were infected by some kind of mold, or rot,
that attacked the basal stems and turned them to mush. I threw them and the
potting media out after treating them with a fungicide to no avail. Never
did find out the name of the infection, but it developed extraordinarily
quickly.
I do NOT recommend using a soap and/or nicotine spray on droseras or near
the crowns of ANY potted CPs. Some Nepenthes may be treated in this manner,
but care must be taken to avoid open pitchers and to keep such mixtures
away from the growing medium.
Don't know if this helps, but Good Growing,
Rand Nicholson
The Writing Service
Canada
writserv@mi.net