This is iris leaf spot. Some years it's a nuisance, other years not. You can spray with a fungicide to limit its spread. And/or cut away unsightly portions. I haven't heard proof positive stories about organic recipes. I have used my rose fungicide on it with success of limiting its spread. Other people swear by Danconil (sp?).

Good news is leaf spot is non-threatening. Bad news, it's ugly. One year might be bad, the following year none. Or it may appear for a couple of years in a row.

Many precautions have been suggested but in my experience none really works. We've had an unusually high amount of rainfall this year and yet I'm not seeing it. So much for that theory. The one year it was so bad I swore I would spray all new growth regularly the next season. Forgot. Very little appearance. No figuring this one.

A search on leaf spot in the box at the bottom of the page will bring up old posts on the subject.

Thank you! I think I can handle that :)