INJURY TO TREES
hi, we have a plum tree and a maple tree both showing the same injury. The plum is about 17 years old, growing in sand on Breezy Point, NY as is the maple. A split started in the plum tree some five years ago and continues to get worse with what looks like clear (amber like) sap hardening as it drips out of the trunk. The wood of the tree grows into the crack on the bark and seem to heal itself then the cracking moves up the tree and to other limbs. The injury started at the base of the trunk and has spread upwards. Part of the plum tree has died. I don't see any critters on it, but see some of the bark coming away from the trunk. The same injury started on the maple 2/3 years ago. We had 7 ft of water during hurricane Sandy in the garden and standing water for about 3 days. i can't seem to upload pictures, your page won't load them - sorry
Queens County New York
We can see two of your photos, of the plum tree. It certainly seems as if it is in decline. There are many possible reasons, as ornamental fruit trees can have many problems and are generally not very long lived.
Here is our Extension publication (U of Maryland) about tham:
The amber sap suggests some sort of bark injury. It could be mechanical (man-made) but not at all unlikely, could be due to a boring insect.
We'd suggest pruning out all the dead wood now and seeing what you have left to decide whether it's worth keeping. It would tidy it up, and though once borers are in a tree (they are often drawn to stressed trees, especially from drought) there is not much to be done, they can last quite a while, especially if given care such as watering during times of less than an inch of rain a week, and a mulch covering of 2-3 inches (not touching the trunk) to keep in moisture and lessen any competition from nearby weeds and plants.
Here is our IPM Shade Tree publication that should likewise help you with your maple tree: http://extension.umd.edu/sites/default/files/_images/programs/hgic/Publications/HG61_IPM_Series_Shad...