Thanks for the question. To identify a possible treatment will require finding the cause of the canker. Our hot and droughty conditions can weaken our trees making them susceptible to various maladies. Have you noticed any other symptoms (dieback, early shedding of leaves, smaller leaves, etc.)? When did you first notice the problem? Knowing the soil type, irrigation, age, recent damage, canker location (e.g. north, south) can also help it determining the problem. Could you verify that the canker is "bleeding". One concerning factor is the apparent lack of root flare at the base of the tree, possibly improper mulching. This can cause decay at the base of the tree. You can also get a diagnosis by sending a sample to the Plant and Pest Diagnostics Lab (https://www.canr.msu.edu/pestid/) or have an onsite visit by a certified arborist (https://www.treesaregood.org/findanarborist).

I look forward to your response,