Answer: Unfortunately, based on the fact that it was recently pruned severely I suspect the stickiness may be exuding sap and that, along with staining of the bark, are characteristic of an infection. There is a potential for severe disease which will attack wax myrtle through cuts, either Inonotus heartrot or Ptychogaster wood rot (Inonotus rickii or Ptychogaster cubensis.) I would strongly suggest you work with your local county extension to obtain a specific diagnosis of the problem and based on knowing that, decide how to proceed. I am really sorry.
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