Yellow-bellied sapsuckers and verbena bushes

I've got yellow-bellied sapsuckers who are doing a number on two verbena bushes with the grid that they carve into the bark to extract the sap. In past years, the bushes have done fine, but this year, I'm more concerned because the grid is much more extensive. Will this do any permanent damage to the bushes?
Tracy Lewandowski Louisville, KY
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