juniper tip blight or diplodia

I have a question concerning what was diagnosed as Juniper Tip Blight or diplodia. I have an ashe juniper with 'rust' on the growing tips. I pluck the dead tips off and have been spraying with a copper fungicide but it has not abated or stopped or contained the spread. If left unchecked the tips die, then the twig, then the branch, etc...
I believe the cause was too much overhead watering - now all overhead watering has stopped.

Any help or suggestions will really appreciated. Thank you in advance.