I'm just guessing here - maybe rust?

this is from mobot - Problems Associated with Arisaema dracontium - Rusts Page
Quote from above:
"Symptoms may include leaf yellowing, withering and early leaf drop. In some cases at the time orange spores of the fungus are produced, lesions are not yet evident."

this and other issues listed in link below

hope everything works out - it's a beautiful plant.

Here is a link that might be useful: Problems Associated with Arisaema dracontium

Thank you so much, bubbleoffplumb!

I'm guessing it must be some kind of fungus. I don't usually apply garden treatments to the plants that grow wild around here, but surely a fungicide couldn't harm it any worse than this disease.