Growths on blueberry bushes
That is blueberry stem gall wasp. The wasp lays its eggs on the stems during bloom and the larvae caused the stem to enlarge and protect them then through the season. The treatment window is just before and after bloom since the insecticides that will kill the gall wasp and its eggs will also kill bees.
This is a native blueberry pest which has become very abundant in the last few years especially in northern Michigan. What variety is it on? It appears to be selective as to the varieties it goes to if it has a choice.
At this time the best course of action is to cut it all out and destroy the galls.
Here is some more information on the pest
If you have any other questions please contact me directly.