An increasing reliance on herbicides in farming has resulted in many weeds developing a resistance to a range of chemicals. At the same time, new crop types, tolerant to specific herbicides, are being developed by biotechnology.
Herbicide resistance is now a major problem in Australia, with one in five farmers being affected. The world's most spectacular case of herbicide resistance is the Australian grass weed Lolium rigidum. This plant has demonstrated resistance to many different herbicides in thousands of populations.