Uromycladium species (Acacia rust fungi)
Order : Pucciniales
Species: U. notabile
Scientific name: Uromycladium notabile
Synonyms: Uredo notabilis
Uromycladium notabile is a fungus whose host are trees of the Acacia species. It is distributed throughout New Zealand. The fungus attacks stems, branches, mature seed pods, and leaf petioles forming large, convoluted, brown galls on branches, stems, and seed pods. These galls can range from 2cc to 35 cm across and they continue to grow for several seasons. They restrict water conduction within the tree and as a result, branches beyond the galls make little growth, produce few leaves, and begin to die back. When infection is severe, whole trees may be killed outright.
Each season the galls surface can become completely covered with brown spores and are spread by the wind and infect other trees by entering natural openings. The release of hormones by the growing fungal spores stimulates the growth of tree cells. This growth rapidly produces galls. The swelling gall tissue emerges from with in the infected stems and then grows externally. The galls produce spores from end of March and throughout winter. During August the galls begin to die and spore production ceases. Some galls on larger branches may survive and produce wart like outgrowths bearing spores in the following year.
Old galls are frequently attacked by insects and extensive tunnelling by larvae can be found. These insects, however, live at the expense of the gall and do not affect the host tree.