As it happens I was editing an article for the UKCPS journal last night and
I came across a reference to soft soap as a cure for pest diseases.
Apparently the stuff works by destroying the waxy cuticle of the insect.
which then dies of dehydration. It ought to therefore work on most sap
sucking pests which form such cuticles but beware since the soap will also
have a similar effect on the plant.
Accordingly I'd try it at a weaker than recommended dilution first and test
a small part of the plant to cxheck for adverse reactions.
My guess is that you would need to be especially careful with Pinguiculas
and Drosera since the digestive areas which have the thinnest cuticle are
on the outer surface of the leaf. Sarracenias, Utrics, Nepenthes etc all
have the digestive areas tucked away so are less likely to be affected.
-- Phil Wilson (cp@pwilson.demon.co.uk)