[Highland Park] certified arborist

Hello neighbors! We have a regular tree guy - for tree removal and pruning - Bert Ackerman 412-521-1938. He's great, not cheap, but reliable. He shows up when he says he will and does the work and a great clean up at the quoted price. We've dealt with him for close to two decades and have always been delighted. However, I now need a certified arborist. While cleaning ivy around my 100+ year old Norway maple, I found a patch of black fungus. Would hate to lose that tree. It provides comforting shade to the yard in the morning and the house in the afternoon. Can anyone recommend a certified arborist to help me with that problem? Thanks. Jan M.