There is a nearby Linden tree which was in a bit of decline last year. This spring it was slow to leaf out. When it did, there were fewer leaves than last year.
One classic symptom of this disease is that all the leaves die on a branch except those at the tip of the branch. This picture shows such a branch taken from this linden tree.
Further away from the tip, as the twig coloration turns from green to a normal bark-brown, what looks like cobwebs start appearing first. Shortly thereafter, it looks like some clumps of brown dirt are mixed in with the cobwebs. A bit further on and spores begin to appear.
As on other trees and shrubs, the spores seem to appear more often near a branch junction or on a leaf stem. On the other hand, they often appear only on one side of the stem and tend to cluster there. This picture shows a cluster of spores on and near a leaf scar.
While the earlier pictures were taken in late May, the following set of pictures were taken in late September. At this time the white canker had already reproduced by shedding it's spores. Hence, spores were hard to find in the following branch and leaf cross-section microscopic views.
The inner bark is pretty much corrupted by white canker. (400x)
Large chunks of canker are errupting from the vessels. (400x)
Ice-white white canker hyphae are heavily colonizing the bark. (400x)
Parts of the inner conducting sapwood are also being blocked due to canker growth. (400x)
Lots of canker and tissue corruption. Also, note the white hypha coming up through a vessel, exiting the bark, and generating a blob of white canker outside the bark (red arrows). (400x)
Here, as in several other areas, the canker seems to follow rays leading to the branch center. Also, note that canker growth has separated the bark here (red arrows). (400x)
Here is good evidence here for distinguishing white canker from a leaf vein, which also tends to be white. The canker tends to run from the top to the bottom of a leaf. A vein is round, white, and frothy, and the leaf tends to bulge around it. (400x)
Two definite white canker blobs on the bottom of the leaf. (400x)
More instances of white canker extending from the bottom to the top of a leaf. (400x)
White canker runs from the top to the bottom of the leaf here, and some pieces of it are being shed from the top of the leaf. (400x)

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