Diseases and disorders of olives in Australia

A survey of diseases in olive plantations throughout Australia was undertaken during 2001-2005. Olive trees with disease symptoms were tested to determine the causal agent(s). Where new pathogens were detected, greenhouse studies were undertaken to confirm pathogenicity. Leaf diseases detected were olive leaf spot (Spilocaea oleagina) and cercospora leaf mould (Pseudocercospora (=Cercospora=Mycocentrospora) cladosporioides). Anthracnose (Colletotrichum acutatum, C. gloeosporioides) was the main disease of fruit, however the physiological disorder apical end rot was prevalent and caused significant damage to fruit. Verticillium dahliae and several Phytophthora spp. were recovered from trunks and roots of wilted and dying trees. Several bacteria, including Pseudomonas syringae, Ralstonia solanacearum, Xanthomonas campestris and Pseudomonas sp. were isolated from wound sites, causing stem cankers and local lesions. Two diseases detected for the first time in Australia included olive knot (Pseudomonas savastanoi pv. savastanoi) and charcoal rot (Macrophomina phaseolina=Rhizoctonia bataticola) which caused a dry rot of roots and crowns.