A few days ago, I noticed some black spots on the stem of my 2-3 year old Sunshine Blue blueberry bush. Today, I checked again, and it seems the whole stem is turning black. I just planted the bush this year, and this is one of the original canes that was already on the bush when I planted it. I checked the rest of the bush, and found a smaller patch on a new growth stem that's branching off of a different cane. The lesions on the newer growth appear to be dark reddish colored, while the more extensive ones on the orginal cane appear to be black. I looked it up on the Internet and it looks like stem canker. I'm attaching photos. Should I prune off the affected branches now, or should I wait until the plant goes dormant in winter? Thank you.