Probation officers (P.O.s) routinely check, in the course of their service, for arrests and convictions within and outside the county of jurisdiction. Preemptive disclosure is up to you. Sometimes P.O.s will wait to see the outcome of the new charge before violating you. Depends. Probation violations may not result in the imposition of jail time for the new charge. No false hope here. Each case has its own facts.
If you see your P.O. and do not disclose your new arrest during your scheduled meeting, the P.O. will not appreciate your concealment of the arrest that occurred before the meeting. Your new charge is drug related, as was your prior conviction. Might trigger some modification of your probation regarding a treatment program. No guarantees, but, you are concerned with damage control.
This answer is offered for informational purposes only. It is not offered as, and does not constitute, legal advice. The answer presumes you are not currently represented by an attorney who knows your specific circumstances.