This one can be quite serious...If you have plants that are infested with
sucking insects on the lower leaf surface, their "honeydew" drips down
onto the upper surface of the leaves below.  This sticky material is home
to many fungi which can severely damage a greenhouse crop in a very
short time.  The adults are often trapped in the slime giving the appearance
of a pinguicula, perhaps.  The Rhodo may be "bugged."  If inspection reveals
aphid larvae or white-fly larvae, I would wash the leaves and spray the
lower leaf surfaces with some Safer's soap.  The stickiness of young leaves
could also be natural...but this would be an exception.
ross
Ross Koning                             Internet: Koning@ecsuc.ctstateu.edu
Biology Department                    Phone: (203)-465-5327
Eastern CT State University         Fax: (203)-465-5213
Willimantic, CT  06226  USA