Looks like Botryosphaeria canker. The disease is most severe in woody plants weakened by drought, winter injury, sunscald, poor pruning, low or unbalanced nutrition, fire blight, and black rot. Also called Bot rot, it can be sporadic in appearance, being serious one season and difficult to find in succeeding years. I suggest cutting effected canes and burning them. Make sure you also get all the leaves of the cane that fall to the ground. And try spraying a mixture of one cup of hydrogen peroxide and 1 gal of water. Once a week. Hope this helps.