Invasive Pathogens in Plant Biosecurity. Case Study: Citrus Biosecurity

Most of the world’s major citrus production areas were developed outside the citrus centres of origin, separated from many co-evolved natural enemies (pests and pathogens), but progressive globalisation has reunited some pests with their citrus hosts. Additionally, some ‘new-encounter’ pathogens have not co-evolved with citrus. The movement of major citrus pathogens of biosecurity concern is discussed with particular emphasis on tristeza, leprosis, huanglongbing and citrus variegated chlorosis. The chapter details recent attempts to eradicate citrus canker in Florida (USA) and Emerald (Australia) and focusses on the processes and impediments encountered to achieve eradication under very different climatic, legislative and industry conditions. The impact of citrus black spot in areas climatically conducive to the disease and a discussion of fruit as a pathway for introduction of the disease to new areas are discussed. The experience and learning acquired from managing and eradicating these citrus pests will be of value to other countries and regions that are faced with similar pest incursions.