Wish I could help you, but I don't have a clue. For something like this I would hope you have someone half way knowledgeable at a nearby extension service or perhaps a top end nursery. Effective treatment and prevention are going to depend upon on positive ID of what you are dealing with. Could be viral, fungal or bacterial. A copper spray is probably a reasonable choice if you can't get a positive ID for some reason. Now, having said that please make sure what you are dealing with is actually a problem. It is normal for blueberries to have branch tips turn dark and die. In year one green wood, usually unbranched forms. Then the tip turns dark and dies. It won't grow further. The next year branches form on the cane and the tips of these will also turn dark/black and die. It's just what blueberries do.

The tree is a KIngston Black apple which is supposedly highly susceptible to Fireblight. I am hoping water damage is the issue. Fireblight has never been present in our orchard in years past, But I had something a lot like fireblight cankers on a harrwow sweet pear this spring that got pruned out...so my "radar" for it has been turned up. I wish the OFM would leave the apples alone...I see no fruit damage from them, but we get 2 rounds of egg laying in the growing tips, the more significant in the late spring. All our apples get hit to varying extent, but I have not seen the damage in the pears. It's become a growing problem over the last 3-4 years. I have tried to keep up by just pruning out flagging tips, but it has clearly not been enough. I know Scott has had some success with mating disruption and I need to look into that. I think if I could get the timing just right on Bt or spinosad I could hopefully still get things reined in. Barring that my options are limited if continuing to go the organic route.

Thanks for your responses. It's definitely not frost kill. The tree leafed out long, long after the freeze and was not touched by frost. I planted this tree about 9 years ago. It's in full sun, but with very adequate moisture. About 6 years ago, we had three nights of hard freeze in late May, the week before Memorial Day weekend. It lost all its leaves, didn't releaf until deep into July and had considerable dieback. But two years later it had really recovered, put up a strong leader, and last year began to bloom. It leafed out beautifully this year and looked great until the "blight' began. A friend of mine who is a horticulturalist found one reference to twig blight on sourwoods in one of her textbooks on diseases of woody plants. I would really hate to lose this tree. It's been through so much and was doing so well. And the fall color is a spectacular backdrop to a planting of Aster oblongifolius 'October Skies' and together they make one of the great shows of the fall garden for many weeks. I don't know how to post pics, but it really looks bad, mostly leafless except for a low branch which still looks good. Now that the leaves are gone, the tips seem to be dying too.

I certainly would not rip out a tree if I wasn't sure what was causing a symptom on one twig. It could have been anything causing a twig to die, including a mechanical injury. Fireblight sometimes gives clues. One of them is 'Shepard hooking' of a limb. Usually you'll see a canker where the innoculum originates. If you do identify a limb you suspect of being infected with fireblight, removing it from the tree several inches below the infestation is recommended. I've never waited for dormancy to do it, but some sources say you should. Fireblight is related to weather conditions and I have a wildling apple tree where fireblight was observed one year on several limbs of the tree where I could not reach it to prune (standard apple on own rootstock) and it has not harmed the tree, affected the fruits or reappeared. It can happen to stock of any rose-related tree or shrub, and it can be spread, so do you have numerous apple trees or ornamental crab apples? The infection can be self-limiting or devastating in a tree. Monitor it to see if it recurs elsewhere on the tree. If you do see more damage, I'd call your extension agent for recommendations. Royalty Crabs are susceptible to fireblight. Try to choose varieties resistant to this disease.