I wrote a month and a half ago asking for feedback about a mysterious disease my 2nd-year pear tree came down with. I got some good suggestions, but unfortunately to no avail; the tree isn't making it. This is now the third bare-root pear this nasty disease has taken. It does not appear to be fireblight, as there is no softening of the tissue (rather the opposite), no drippy stuff, and no overall blackening of the leaves with them still on. It could be, though. I wouldn't be surprised. Anyway, here's a description for anyone who wants to take a crack at it. I'm looking for an ID, and preventative strategies. Especially preventative strategies, since hope spings eternal, and I have another young tree out there.

1. In one case, it came on during the first year. In the other two, it appeared during leaf-budding time. When it came on after leaves were out, they looked like this:

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2. it attacks via buds and pruning cuts (as might be expected). Here's what they look like:

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3. Eventually, the whole twig gets blackend, dried-out looking, and brittle, and it travels along towards the crotch. The latest tree also has some vertical cracks in its bark, don't know if that's related:

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Any help would be fervently appreciated!

Jessica