The Director of Public Properties shall have power to enter upon any private grounds in the City and cause to be sprayed or otherwise treated any tree or shrub infected or infested by any parasite or insect pest when it shall be necessary in the opinion of the Director to do so, to prevent the breeding or scattering of any parasite or animal pest, and to prevent danger therefrom to shade trees and shrubbery planted in the streets, alleys and public grounds of the City. Whenever in the opinion of the Director, trimming, treatment or removal of any such tree or shrub located on private grounds shall be deemed wise, the Director shall have power to trim, treat or remove any such shrub.