ABSTRACT
To the general public, weeds are the unwanted plants that grow in their garden and backyard. But the problems associated with the establishment of unwanted plants in agricultural systems and natural ecosystems are far more serious and costly. It was estimated in 2004 that weeds conservatively cost Australian agriculture between $3.5 and $4.5 billion annually (Sinden et al. 2004). Although to date the cost of weeds affecting natural ecosystems has not been adequately evaluated in Australia, some biologists have placed the cost of weeds in these systems in the same order of magnitude as that of weeds of agricultural systems (ARMCANZ 1997). Competition from weeds can have significant negative impacts on native flora and fauna, and some weed species can alter natural ecosystem processes such as fire regimes, flooding regimes and other aspects of hydrology.
