[Arid_gardener] Question: Trees, Mulberry, Leaf Drop, Maricopa County

[Jon Peters]

I have 5 mature mulberry trees all the same age (15yrs old) on the West side of my NW Phoenix home on a flood irrigate(d every 2 weeks), 1 acre lot.  They are all aligned in a N-S direction, spaced 20 ft apart.  Four of them are very healthy, good canopy.  The northernmost mulberry tree has been dropping 90% of its leaves since spring.  The leaves that remain on the tree are curled, and some are yellow (much like the tree was preparing for Winter.  There are no sap or drippings from the tree.  
1) What is the cause and remedy?
2) If it is a disease, how do i prevent it from infecting the remaining trees?


Thanks,

Jon Peters
e-mail: petersjc at earthlink.net