Is my Yoshino cherry tree dying?

[Funksters5]

The leaves of my cherry tree are turning yellow and falling off & sap is coming out of the trunk. Would you look at my pics and tell me what I can do to save my tree. Thanks.

 

[Urban Forester]

Could we get a closeup of the "white substance" on the trunk. The color loss in the leaves is consistant w/a lack of water movement.

 

[treeseer]

also a picture of the first root as it comes off the trunk is important to see.