CULT: Leaf Spot
When I lived in Kentucky, I noticed that some Irises were more
susceptible to leaf spot than were others. In the cloudiest seasons, the
problem was especially severe. However, under no circumstances did I treat
the Irises with chemicals, because I felt the Borer control was enough
poison for a year.
What I always did was keep removing the infected leaves. Once the
heat of summer started, the problem went away. I don't know if this would
work in a cooler summer climate like Sweden, but it is worth a try.
Mark A. Cook
Dunnellon, FL. (That pesky gale is still stirring things up.)