In any instance where trees or portions of trees usable as firewood are removed from property under the control of a public utility, pipeline company, railroad, state agency or department, or a political subdivision, that portion of the tree material that is six inches or larger in diameter shall not be destroyed by open burning or deposited in a landfill without first having been offered for use to the public, subject to the approval of the landowner or landowners involved. This section shall not apply to tree material removed in a program of sanitation or disease control, as defined in Minnesota Statutes 1979 Supplement, section 18.023.