I suspect water pressure damage from excessive water uptake from all the rain you have been having.
From: Barb Jackson <email@example.com>
Sent: Mon, Jun 13, 2011 9:17 pm
Subject: [iris-photos] Strange Markings on TB Stem
My sister and I have discovered a couple of TB iris with a pattern of
marks on the stem just under the first branch on different stalks.
There have been no bugs noticed in either area and the stem was not
staked. The top of the attached photo (with apologies for the quality)
is where the branch starts.
Any ideas welcome as to what might have caused the marks.
BJ in SW MB, Canadian Prairies, Zone 3(ish)