All plants get diseases and most of them are caused by fungi. Some of the worst groups are Fusarium, Ganoderma and Armillaria. From our research at the Royal Botanic Gardens & Domain Trust we have discovered a number of fungi new to science, and new diseases affecting Australian plants - not only in botanic gardens but also in our forests. We think only about 15% of the fungi in Australia are known, and only a fraction have been studied in detail. By understanding which fungi cause diseases, and by researching their biology, we can predict how they can best be controlled.