Re: Strange spots on leaves
Guess it's about time for me to put my 2 cents worth in here on this topic.
I have found that during periods of heavy rain that spores which live
normally in the soil are splashed up onto the leaves and germinate (?)
sporulate (?) resulting in the brownish spots. The causitive agent is
described in "Garden Irises", on page 106, as Heterosporium Leaf Spot (H.
gracile). The same problem is described in "World of Irises", on page 340,
under the heading Fungal Leaf Spot.
While the spot tends to detract from the overall appearance of the clump, IT
IS NOT FATAL, and will disappear as soon as the weather changes to dry. You
can spray anti-fungals but you would be better served to save your money.
There are no iris that I know of that are totally immune to leaf spot but if
you search your garden you will find many iris that are less susceptible.
P.S. There is a picture of leaf spot on page 105 of "Garden Irises"
Regards from Dave Silverberg where leaf spot is a way of life in the wet
Pacific Northwest. But it all disappears when the weather dries up from June
15 to late October.