Looks like Southern Blight or Petiole Rot.

Steve

Here is a link that might be useful: Southern Blight

Here's another thread from earlier this summer concerning Southern Blight...

Here is a link that might be useful: Southern Blight

Thanks Steve and Ci lantro. Those links are exactlly what this looks like. Hopefully I cleaned it up enough.

Better spray the hostas around it with fungicide as well. And if I were you, I'd spray Guac again in the fall, and again in the spring. A hosta grower told me tebuconazole works too.

Deanna