I wonder if the actual status of the leaf itself might confuse the issue even more.
What I mean is, what constitutes a "dead" leaf?
If a leaf drops but still has some moisture content, and/or green tissue, is it considered dead, or does it have to be brown, dry and dessicated? Seems like the leaves when they first drop might still have tissue that could support fungal growth, but once they're brown and really dead, they might not.
Think I'll still pick up all the dropped leaves to try to keep the fungus from spreading.
