Question
I have several of my indigenous (zone 6b) trees in containers as outdoor bonsai.  I'm having a problem with a few of them this summer and I can't seem to identify/treat it.  Specifically, my Black Birch and my Maple have a condition in which about 50%(or more) of the leaves are somewhat shriveled and brittle to the touch (they sort of feel like a dry dead leaf, although they are still on the tree).  For the most part the leaves maintain there green color but some are begining to brown around the edges. While the plants clearly aren't thriving, they don't seem to be completely overwhelmed by this either (at least not yet!).  These are trees that I've owned and grown for several years so I'm fairly certain I have the light/water requirements on base.  I've tried the standard insect sprays with no results.  Any idea what it may be and how to treat it?  Thanks.

Answer
BC,

It is hard to diagnose these type of problems over the net without seeing them.

My first inclination is to suspect water.  I have been noticing these symptoms during drought on water stressed maples.

As far as insect are concerned look before you spray.  If you see insects take a sample to a local expert for ID.

I hope this helps.

Gary