Hesler & Whetzel (1917) claim, "Ten per cent rusty plants are frequently reported.

It can stretch as far south as Florida, or as far west as California, and is also quite common in Europe and Asia (the disease cycles of this rust that are found in Europe are considered "long", as opposed to some of the "short" cycles found in the United States.

Several weeks after the initial appearance of the bodies, a rust will begin to form on the underside of the leaf.

[6] The haustoria penetrate through cell walls to extract nutrients, while the fungus follows the growing-tip of the plant.

As discussed in the "Hosts and Symptoms" section, black bodies appear on the upper surface of the leaves during the spring.

The orange "cushions" that develop later on the under-side of the leaf are forming spores, which have the capability to germinate all at once.