Hoping someone can help, please.

I have a well established (15 years +) berberis. Sorry I don't know the
variety, but it's bronze with small yellow flowers. The last couple of
years, every leaf it produces has been eaten by something so that it's
bare by the end of summer. Caterpillars possibly ? It's just starting to
come into leaf now, and I'd like it to keep its leaves this year if at
all possible.

Short of picking the pests off by hand, what organic methods can I use
to keep them away ?
--
Judy
http://members.lycos.co.uk/bluelotusrising/index.html
http://www.rigbys.demon.co.uk