This freely available and excellent document published by the “Commonwealth of Australia, Rural Industries Research and Development Corporation”. Acknowledgement is made of the copyright of this document but the publishers also state that “The information contained in this publication is intended for general use to assist public knowledge and discussion and to help improve the development of sustainable regions” and that “wide dissemination is encouraged”. We trust that placing this document on this site for convenient and topical access by the club members in particular will be in the spirit of these intentions.