Annette, have you seen any infected plants near your property or in neighboring yards? There's probably a "Typhoid Mary" lurking about nearby. A hiding culprit in my yard was growing up the middle of a large blue spruce. One day I just happened to see something growing out of the upper part of the tree, and it was a huge, heavily diseased multiflora. There were also some in farm fence rows near the drive way.
Chelle, are your Freisia plants grafted or own root? Have they been blackspot resistant as well? I've been choosing mostly fragrant varieties as well, nothing makes me happier than burying my face in a big, fragrant rose! And when I smell roses while just walking around the yard, I'm in Heaven!
