Trace Forward/Trace Back Investigations. When P. ramorum is detected in a nursery, county agricultural commissioners will conduct trace forward and trace back investigations at locations in their county that have either supplied (trace back) or received (trace forward) plants from the positive nursery. Trace back activities include inspection of source nurseries for symptomatic plants, collection and submission of samples, and any other regulatory activities such as issuing hold notices and submitting inspection results.
