Late last summer our ~15 yr old Yellow Bird Magnoila died very suddenly. It began with the leaves on entire branches on one side of the tree turning yellow, wilting and dessicating rapidly. Within 2 weeks one half side of the tree was affected. By late October the entire tree was brown and crispy. The tree failed to leaf out this Spring. Culturally nothing had changed and the tree had been growing vigorously in the same location for about ten years. Surrounding herbaceous plants looked fine. Herbicide damage was not an option. I suspect some kind of pathogen. Does anyone know what could cause such rapid decline in Magnoila? Is the taxon Yellow Bird prone to any particular diseases?