It is effective for Crappie but as I understand it the Grey Ghost Streamer was originated by Carrie Stevens for Big Brookies and Landlocked Salmon in Maine around 1924. Since then many flies, poppers and jigs have come along that imitate the coloring and sometimes steal the name. Especially a Gray Ghost Jig that been around for awhile and is a super popular Crappie jig although some jiggers refer to them as flies. Of course fly fishing was around for a long time before Carrie Stevens came along with her famous flies and for sure it may have been a crappie fly originally but I've never seen anything mentioned along those lines in the historical books on flies. A couple other traditional streamers that work are the Black Nosed Dace and the Nine Three. Crappies have a big mouth and those streamers slim down in the water so they hit them quite well at times, especially when they are chasing minnows rahter than sitting on or near nests as then they like it slow and maribou rules. Another one I like is one called the Warden's Worry and along with it any of the Muddlers in smaller sizes.