Weston (1957) stated that this gall-forming rust fungus was introduced on seedling plants [of Acacia] from Australia. It attacks stems, leaf petioles, and mature seed pods, forming inflated galls several centimetres in diameter. Cunningham (1926c) stated that this fungus has proved to be serious on Acacia grown for ornament and for tan bark. Weston (1957) stated that by 1920 the rust fungi Uromycladium had spread throughout both islands and by 1930 the presence of this disease made the tan bark plantations uneconomic and they were felled and cleared.

Type: Rust and Smut Fungi; Description: Spermagonia black, pustulate, minute, associated with both uredinia and telia and covering the entire surface of inflated convoluted galls; on stems, branches, petioles, and seed pods. Galls are perennial, usually 2–8 cm in diameter but up to 35 cm; on petioles and seed pods they are smaller, with a blister-like, green to purplish appearance; stem and branch galls are usually larger and olive brown. Uredinia cinnamon brown, mixed with chocolate brown telia. Urediniospores ellipsoid to oblong, 30–45 × 16–26 μm, bright yellow becoming yellowish brown, reticulate; pedicel elongated, hyaline. Teliospores three in a head on one sporophore, which does not have a lateral vesicle; teliospores depressed globose to subglobose, 16–23 × 21–26 μm, pallid chestnut brown, densely covered with warty spines arranged in lines.

Distribution: Northland, Auckland, Coromandel, Waikato, Bay of Plenty, Taranaki, Taupo, Rangitikei, Wanganui, Gisborne, Hawkes Bay, Nelson, Marlborough Sounds, Marlborough, Mid Canterbury, Dunedin.; 1st Record: Cunningham (1923a).

Significance: Because galls impede the transpiration flow, branches beyond the gall make little growth, produce only a few leaves and begin to die back. When infection is severe, whole trees may be killed within a few seasons. In the 1920s, this rust was responsible for the failure of 1800 ha of Acacia decurrens planted to start a tannin industry. Until recently, susceptible host species were not grown commercially but there are plans for planting substantial areas of A. mearnsii and A. dealbata in Northland. At present, the effect U. notabile on these plantations cannot be predicted.; Host(s): Acacia baileyana, A. dealbata, A. decurrens, A. mearnsii.