Bright white fungus, what is it?

[Almighty Beech]

Hi all,

 

At Rutland County Council we are proud to have three mature elm trees, sadly a sporophore was discovered on one of these trees. Unfortunately someone unknown has remove most of it restricting my ability to identify it. It is pure white with a fine grey horizontal layers; 8.5cm width; 6cm length.

 

I have spent sometime trying to narrow down what it can be, and then conclude how significant this disease is to the tree. Any help will be greatly valued. 

[Steve Bullman]

Maybe fomes fomentarius?

[scotspine1]

Perenniporia fraxinea