I recently moved to az. From Ca. and was arrested here for poss. Of marijuana... I'm on informal probation in Ca. for DUI... is my recent arrest a probation violation in Az. Do I need to report to the court that I'm on probation in Ca. before my pretrial?

Your probation will show up on the criminal history in AZ and it will show up. What you do have to do is inform CA that you have been arrested in AZ.

Not informing the PO of any police contact is considered a violation of your probation. Tell them before they find out about it on their own.

In addition to the above, in my state an arrest does not violate probation, only a conviction.