or similar modes of action and combining chemicals with other weed control methods; this is called 'Integrated Weed Management'. Farming practices Herbicide resistance recently became a critical problem as many Australian sheep farmers switched to exclusively growing wheat in their pastures in the 1970s. In wheat fields, introduced varieties of ryegrass, while good for grazing sheep, are intense competitors with wheat. Ryegrasses produce so many seeds that, if left unchecked, they can completely choke a field. Herbicides provided excellent control, while reducing soil disrupting because of less need to plough. Within little more than a decade, ryegrass and other weeds began to develop resistance. Australian farmers evolved again and began diversifying their techniques. In 1983, patches of ryegrass had become immune to Hoegrass, a family of herbicides that inhibit an enzyme called acetyl coenzyme A carboxylase. Ryegrass populations were large, and had substantial genetic diversity, because farmers had planted many varieties. Ryegrass is cross-pollinated by wind, so genes shuffle frequently. Farmers sprayed inexpensive Hoegrass year after year, creating selection pressure, but were diluting the herbicide in order to save money, increasing plants survival. Hoegrass was mostly replaced by a group of herbicides that block acetolactate synthase, again helped by poor application practices. Ryegrass evolved a kind of "cross-resistance" that allowed it to rapidly break down a variety of herbicides. Australian farmers lost four classes of herbicides in only a few years. As of 2013 only two herbicide classes, called Photosystem II and long-chain fatty acid inhibitors, had become the last hope. Weed societies Internationally, weed societies help collaboration in weed science and management. In North America the Weed Science Society of America (WSSA) was founded in 1956 and publishes three journals: Weed Science, Weed Technology, and Invasive Plant Science and Management.'' In Britain, European Weed Research Council was established in 1958 and later expanded their scope under the name European Weed Research Society The main journal of this society is Weed Research. Moreover, the Council of Australasian Weed Society (CAWS) serves as a centre for information on Australian weeds, while New Zealand Plant Protection Society (NZPPS) facilitates information sharing in New Zealand. Strategic weed management is a process of managing weeds at a district, regional or national scale. In Australia the first published weed management strategies were developed in Tasmania, New South Wales and South Australian 1999, followed by the National Weeds Strategy in 1999. See also Control of Bramble