India, Oct. 20 -- A tree brought in to help Australian farms has become one of the country's toughest weed problems. The Northern Territory Government says prickly acacia was first introduced to Australia as a shade and fodder tree. It now infests more than 6.6 million hectares of the country and is listed by the government as a Weed of National Significance, a national label applied to weeds with major impacts.

The tree is native to tropical and subtropical Africa, Pakistan, India and Myanmar. It came to Australia in the 1890s for shade, fodder and ornamental purposes, according to a 2003 study by Kriticos and colleagues in the Journal of Applied Ecology. By 1926, it was established in the Bowen and Rockhampton districts of Queensland. ...