Experts and BHG readers answer.
weeping willow leaves turning yellow
Thanks for writing. It sounds as though your willow may have a fungal disease --- but without being able to examine the plant in person, I can't really say what disease it would be.
For more help, I'd contact the experts at your local county extension office: http://www.aces.edu/counties/Tuscaloosa/ They should be able to help more if they can come out and look at your tree.
---Justin, Senior Garden Editor, BHG.com