Alfalfa Disease

I'm trying to identify a disease in my alfalfa. We've been having lots of rain and cool temperatures, and I'm on heavy black clay (not the ideal alfalfa soil). I think I've narrowed it down to Pyhtophthora root rot or brown root rot, but maybe something else. I first noticed yellowing of the leaves. When I walked out into the field, the crowns were crunching like it is August and I didn't irrigate it. The leaves are dying from the bottom up. I dug up a crown today and broke it open. Has some brown rot in the root, just below the crown. The stems broke off from the crown easily.

 

The WL rep said brown stem rot. Is there a difference from brown root rot or the same thing?

 

We have cotton root rot, but I know that's not it. Cotton root rot is more common for us, as well as constant insects pressure.

 

Thanks for any help.

 

 

 

 

Alfalfa Disease