The effectuate the purpose of this article, the commissioner is hereby invested with authority, during reasonable working hours, to enter upon any public or private premises, except private residences, to examine and sample all plants and trees, soil, articles, and substances which are suspected of being infested or infected with dangerous plant pests or other insects or noxious weeds in discharge of the duties prescribed by this article. No person shall obstruct or hinder him in the discharge of his duties.