Greetings Marjorie:
Premature leaf drop, if indeed this tree is dropping its leaves prematurely, is often the result of either environmental factors (heat, drought, excess moisture, flooding, altered soil hydrology, etc.) or biological factors (insects and/or pathogens).
Since most individual tree "health" symptoms cannot be effectively diagosed over email, phone, or the internet, please contact your local university Extension office or contact a local certified arborist for an on-site evaluation of the affected tree.
Best of luck!
