Here's some considerations:
*The large vertical wound looks to be a result of a lightning strike.
*The spongy friable material is all-dead heartwood, decomposing in place.
*The regularly accumulating sawdust is most likely decompositional insect derived, probably ants now. It could also be the result of woodpeckers or other birds foraging for insects.
*The holes might be the result of borers or some other insect, but that is probably the least of this tree's problems.
PRESCRIPTION
Clean up the edges of the bark along the wound, trimming back dead/dry till encountering green tissue. This will be the beginning of the live callous tissue that will be trying to close this big wound.
Remove as much of the spongy and friable material as possible, again back to hard stable wood. The spongy friable stuff is just providing a home to insects and other decay organisms like fungi or bacteria.
In fact, the systemic insecticide would probably do absolutely nothing towards eliminating any of the problems that appear to be there, since none of them are occurring in live wood where the systemic insecticide might be circulated to.
