Question
I live in NJ and have barberries throughout my landscaping.  The last couple years I noticed in summer, they seem to become infested with something that feeds off the leaves and stems and leaves debris behind, showing signs some kind of insect has been living there.  It doesn't appear to be any type web.  I haven't seen any insects on the plants but it started with one plant and keeps spreading around the property - but only to the Barberries.  I have sprayed them but it still comes back every year.  

Answer
Carly,

There are several possiblities- Barberry Aphid, Barberry Webworm or Scale. In all cases I would recommend spraying the insides of the shrubs with horticultural oil now to suffocate any overwintering insects or egg masses.

Good luck,
Ed Gulliksen