I have a Brogdon variety which is about 1 1/2 yrs old and looks very healthy. However, this spring shortly after it put out new leaf shoots, I have noticed several vertical splits in the bark right through the cambium and above the graft. I also noticed higher up on the tree, there is a spot where a whitish material was forming, and I saw a little 1/2" brown lesion there. On digging down with an xacto, I notice brown tissue down quite a ways. Although the tree looks healthy otherwise, is it now infected with some God awful systemic disease?

I have included a picture of my tree taken back in the fall.

Here is a link that might be useful: