Report Title - Weeds Australia

Figure 1Life cycle of prickly acacia2.2 History of spreadPrickly acacia was first recorded in Australia in 1803 in New South Wales. It did not becomewidespread until after 1900, when it was grown extensively as a shade and ornamental treein the Bowen and Rockhampton districts of Queensland. Initial spread was by broadcastingseeds from horseback and by deliberate planting of seedlings. In 1926, the QueenslandDepartment of Agriculture and Stock recommended it as a shade tree for sheep productionin western Queensland. It was subsequently widely planted around homesteads, bore drainsand dams during the 1920s to the 1940s, not only for shade but also for fodder, because ofthe protein-rich pods and leaves.The wool crash of the 1970s saw a change from stocking sheep to cattle in Queensland. Theslump in cattle prices during the 1970s in turn led to high stocking rates, which may havebeen significant in providing large numbers of cattle as dispersal agents. This, and the seriesof wet years during the 1950s and again in the 1970s promoted massive invasion of pricklyacacia throughout the northern Mitchell Grass Downs and the establishment of dense thornveldts, particularly along bore drains.Infestations now cover about 6.6 million hectares, with large established infestationsroughly bordered by Hughenden, Julia Creek, Winton, Barcaldine and Aramac in westernQueensland. The heaviest infestations occur along bore drains, watercourses and drainagelines. Infestations spread from here onto the extensive rangelands.Infestations also occur in coastal and southern Queensland, the Barkly and Victoria Riverdistricts of the Northern Territory, the Kimberley region of Western Australia and the northeastof South Australia.3