A wind driven vertical axis power generating system is disclosed. It is an object of the invention to provide a changer of this kind modified in such a way that the user can access all disks inside the changer and access all disks except disks which are in a playback position by a pick-up or an equivalent reader. The active agent is converted at the application site upon access of moisture and by an activating agent into a second state, which is suitable for diffusion through the skin or mucous membrane and in which it is taken up by the organism. isolates, or toxins therefrom, are used to control alfalfa weevils, boll weevils, andor rice water weevils.