Looks like some kind of bacterial infection or maybe stem borer assuming that all other factors are up to par. What kind of water are you using? Rain water, municiple, well???

The blueberry is planted next to a small pond so does not need watering. Others are planted 50 feet from the pond and still has this problem.

It could be a stem canker.What variety of Blueberry?There are canker resistant kinds.I'm not sure which ones though. Brady

The varieties have been forgotten through the years but I'll check out canker free blueberries, Thanks all.

I have the same problem, it's a type of canker. What I plan to do is cut the stems down to soil level and spray lime sulfur this fall and early spring. This is suppose to take care of the canker. worth a try i suppose. luke

Thanks Luke, It's too late for this years treatment but I'll be ready for it next year.

Guate, that looks like phomopsis twig blight to me:

http://ohioline.osu.edu/hyg-fact/3000/pdf/3214.pdf

It wiped out my entire planting, despite my thorough soil preperation. Perhaps if I had caught it earlier, some fungicide might have saved my plants. I now have brambles in the beds--they're looking good.

Marc