Our M. sieboldii has developed some kind of an infection affecting is growth. It was planted 2 yrs ago and guessing it was approx 3 yrs in the pot, prior. Noticed the stem scarring last fall and originally thought it was a "buck in rut" rub damage (he turned a healthy 5 year M. grandiflora into a 6 inch stump over night!). This spring the sieboldii budded out with leaf and flower buds uniformly throughout the plant but in the last 2 weeks one of the main stems exhibiting the most serious scarring/damage has wilted and browned the both leaf and flower buds (some very small shoots appear to be emerging unscathed thou). A secondary stem off an adjacent main stem is also showing same wilt and as well has to a lesser degree the same stem damage. The rest of the plant appears to have good vigor and healthy flower buds. The injury/infection of the stem on closer inspection does not match rub damage and appears to be a dry canker or something within the stem drying the bark out and splitting vertically, partially girdling stem. At present contemplating pruning the infected stems off and thinking perhaps get onto a winter dormancy spray program. Any ID on the pathogen and other treatment options?