The City Arborist shall have the right and duty to trim any tree existing on any public place in the City so as to insure the public safety or to preserve the function or beauty of such public place. He shall further have the right to remove any such tree or any part thereof which is in an unsafe condition or which, by reason of its location or nature, is injurious or detrimental to other public improvements, or is infected with any injury, fungus, insect or other pest or disease which cannot otherwise be controlled. Such infested or infected tree is a public nuisance.