I'm going to take a closer look at the roots tomorrow. All of the other symptoms are textbook symptoms of scorch, so either I found them in time to prevent root damage (unlikely) or I overlooked some early signs of damage. I will also take a closer look at the surrounding iris clumps.
The rhizomes were securely anchored by their roots, I had to dig them out. But other than that all the symptoms were there. The leaves started dying at the tips (but I didn't look close enough to notice that it was the new inner leaves that were dying first), the dead leaves would not pull off, when the outer leaves were removed from surrounding healthy-appearing rhizomes the inner leaves were a sickly yellow green and were limp, the rhizomes were firm, the dead leaves were a reddish brown and looked like they had been burnt. The problem occurred in the bed that had the scale problem late last summer...so it's possible the scale were the vector for the infection.
Since one of the studies said that rhizomes left out in the sun (we are having warm weather) for a long time can be cured...although when replanted in fall they probably won't bloom for a year...I'm thinking I might try to 'bake' a few on the patio for the sake of science. If I decide to try this I will keep them separated from my other plants. I'm not sure I want to risk it though...
