I finally figured out that scorch is the name of the condition that is causing a die off of some of my iris plants. The first sign seems to be a brown dead leaf in the middle of a fan, and when you dig up the plant in an advanced state of scorch, you find that the roots have dried up although the rhizome is still hard and looks fine. I have seen this other years, but didn't really know what it was.
I had some irises that bloomed gloriously this year, and then they just quit growing. I thought it was just the drought so I have watered them a couple times this summer, but it didn't help the ones with scorch. When I dug them it smelled a bit like mushrooms? So I am wondering if it is some kind of fungus maybe. For now I am digging up the ones with this condition and cutting out any of the parts that are still good. New roots will form at the growing edge of a rhizome. So I am sort of experimenting with the sickies to see if there is anything to arrest the disease. Well at least it has cut back on my need for new iris beds!
Hi, While I only know of "scorch" from reading on the forums, and don't think I've ever had it (and don't WANT it, from what I read of your troubles!) I have a "can't hurt, might help"treatment I use whenever an iris comes out of the ground, before I replant. I use an old spoon and a knife to remove any damaged/rotted/soft areas, then I wash it well with a bleach solution( I'd guess 10-20% bleach) ,Lay them in the sun till they are dry(maybe turn them so they dry completely) then I dust them well with sulfer(get the powder, not the flakes), and replant. I like to remove the spent, or in your case, infected soil,and replace with a good mix of 1/3 composted manure,1/3 good topsoil, and 1/3 my crummy,sandy, rocky soil.I replant, water well, and spray them with a fungicyde after a few days. This has taken care of almost all are "ills" ,borer damage soft rot, and even what I believe was crown rot.Anyway , good luck!...Arlyn
From my latest research, scorch is caused by a mycoplasma that is transmitted by leaf hoppers, directly from plant to plant. You have to get rid of all plants that are carrying it, or the bugs will just keep spreading it. A high heat treatment may kill it. Unfortunately, our weeks of 100 degree plus heat seem to be gone for now...(Did I say unfortunately? ;>)