Cultivate your own garden, said Voltaire at the end of Candide. Looking homeward, I note that peony measles, first seen in mid-July has continued to develop. Measles, or red spot or leaf blotch or Cladosporium leaf blotch disease are alternative names for this fungal disease. It is caused by, you guessed it, Cladosporium paeoniae or, who knew, with its new moniker, Dicholocladosporium chlorocephalum.
On the upper leaf surface, reddish and brownish “measles”-like spots develop earlier in summer, now coalescing into purple blotches. I noticed this week a different symptom on the lower leaf surfaces, described quite aptly by Nancy Pataky of the University of Illinois as “dull chestnut brown” in color.