Dear Peter,
I have found that most of the systemic pesticides available here in the U.S.
have no ill effect on Nepenthes when used at recommended strength. I use a
produce called Cygon 2E at 1 tablespoon/gallon. This is very effective
against scale but you may need a second application in 10 days. If this is
not available in your area try a local product on a test plant. When using a
new pesticide you can do a 1X and a 4X test on a couple of seedlings or
something relatively common like N. alata that you would not be overly
concerned with losing. If a 4X test does no harm it should be safe with virtua
lly any Nepenthes. I have heard however that Nepenthes are damaged or killed
by copper based fungicides.
Most of our local scale are easy to kill, however one species known as snow
scale requires repeated treatment with at least two systemic insecticides
over a month or more. It is widespread in the eastern U.S. and may occur in
Europe as well.
Good Luck!
Cliff