Kingdom: Fungi
Division: Basidiomycota
Class: Pucciniomycetes
Order: Pucciniales
Family: Pileolariaceae
Genus: Uromycladium
Species: U. notabile
Scientific name: Uromycladium notabile
Synonyms: Uredo notabilis
Common name; Acacia rust fungi
Uromycladium notabile is a fungus whose host are trees of the Acacia species. It is distributed throughout New Zealand. The fungus attacks stem, 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 within the infected stems and then grows externally. The galls produce spores from the end of March and throughout winter.In 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.
The galls darken with age.
The following photos are of galls on Acacia mearnsii (Black wattle)
Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/
