Herbicide resistance starts with the loss of one or two herbicides but rapidly escalates as the increasing use of a smaller pool of herbicide actives greatly increases the selection pressure for weeds to evolve resistance to the remaining active groups.
The loss of effective herbicidal weed control represents a major threat to food security, as weeds compete with agricultural crops for water, sunlight and nutrients. It can render crop production uneconomical because of its impact on yield and quality, and the higher costs of using non-chemical alternatives, such as tillage, to manage weeds.
In Australia, herbicide resistance and the subsequent loss of economic viability contributed to a substantial reduction in the number of Australian grain growers during the late 1990s and early 2000s, Dr Michael Walsh, professor of plant sciences at Charles Sturt University in Australia, said during a farmers’ day hosted by the Western Cape Department of Agriculture at Tygerhoek Research Farm near Riviersonderend in the Western Cape.
He pointed out that herbicide resistance was a more severe problem in Western Australia than in other parts of the Australian wheat belt, as farmers in this region were more focused on intensive crop production with reduced livestock.
In comparison, growers in the eastern wheat belt region typically have a mixed production focus with an integrated crop and livestock production system, which helped to slow herbicide resistance development.
According to herbicide resistance surveys that are
