Dr Kerr is a distinguished plant pathologist who has recently discovered a method of biological control of the disease crown gall in stone-fruit crops. This disease is estimated to cause annual losses amounting to about $Al38 million in the world, including about $Al.4 in Australia, The method of control, widely practised by growers in Australia, has been introduced into New Zealand, Canada and the USA and is being tested in England and Greece. In addition to this important applied research, Kerr is recognised for his genetic model for pathogenicity in Agrobacterium, showing that the plant tumours result from the transfer of bacterial DNA to the plant cell.