Powdery Mildew disease on leaf. Yellowing patches and dead brown tissue.
Powdery mildew (Podosphaera xanthii) on bottom of leaf. My plant was doing well this spring but once the 90+ degree F weather and 80% humidity hit in May, it got an attack of powdery mildew. Download and zoom in for a closer look. The plant is sluffing off these leaves and I'll wait to see if I need to use potassium carbonate. As you will see from most of these photos, powdery mildew on mirlitons does not progress to a "patch white powder" as in other plants. The leaves yellow and die before the fungus can create obvious colonies.
Healthy leaf.
Early signs of disease, small yellow spots that coalesce into broader yellow wedges.
Powdery Mildew turns tendrils brown.
Powdery Mildew killing young flowers
Leaf-curl resulting from treating plant with potassium carbonate (Milstop). The milstop will burn flowers, kill tendrils, and damage flowers, but this is necessary to kill the powdery mildew. Four weeks of treatment of plant has these negative side-effects but is necessary damage to ensure long-range treatment of the disease.
Healthy leaf after 4-week treatment of plant with milstop.
Powdery mildew infection in spring in plants crowded together against fence, which traps morning fog and reduce air circulation.
Infected leaves
Early infection, faded yellow splotches.