Discovered this grossness on our peach tree:
As far as I can tell from googling, it's got perennial canker, also called Valsa canker, Cytospora canker, Leucostoma canker, and peach canker. Leucostoma cincta or persoonii -- not sure which, not sure it matters.
Canker eradication. During the pruning operation, remove all cankers on small branches or limbs, making a thinning cut at least 4 inches (10 cm) beneath the edge of the cankered zone. On large scaffold limbs or the trunk, it is possible to surgically remove cankers during the late spring or early summer, when the wounds will heal most rapidly. Although this is a time consuming procedure, it is particularly useful for eradicating canker from young orchards in the early stages of disease development, before it has a chance to spread. It should not be practiced when cankers affect more than half of the branch diameter.Gotta do some serious surgery. It's really widespread on the tree. Lots of oozing.
Surgery should be performed during dry weather, preferably when no rain is forecast for at least 3 days. Using a sharp knife, remove all diseased bark around each canker, plus a 3/4- to 1-inch (2-2.5 cm) margin of healthy tissue around the edges; it is not necessary to dig into the hardwood, but there should be no brown inner bark that remains. To heal properly, the finished cut should have a smooth margin and be slightly rounded at the top and bottom ends. It is not necessary or helpful to cover these cuts with a wound dressing.