Cankers can cause poor tree growth and may not be on all branches.
Photo from Dr. Krishna Mohan, ISU.
A cut from a pocket knife reveals that under the canker the vascular cambium is brown and necrotic rather than light green.
OSU Plant Clinic Image, 2018.
See:
Peach (Prunus persica) - Cytospora Canker
Note Out of dozens of samples there were 4 diagnosed with Cytospora canker by the OSU Plant Clinic. Other pathogens associated with cankers in other samples included Fusarium and Nectria as well as bacterial canker.
