Q: Some of our magnolias have leaf “clusters”, that are turning brown . Could you advise us about possible causes?

A: I think the flagging is caused by black twig borer. If it was a twig girdler, you would have complained about lots of twigs on the ground and few in the tree….plus the twig ends would be more conical.

see Black Twig Borer

Black Twig Borer – NCSU

Twig Girdlers