Toodyay Land Conservation District Committee - Herbicide Resistance



	Publications Weeds Soils Species Lists Catchments Phillips Brook Wattening Jimperding Boyagerring Community Friends of the River Seed Orchard Naturalists Club Issues Salinity Sodicity Revegetation Erosion Livestock Management Advice for the Small Landholder Small Landholder Information Service Spatial data Shared Land Information Platform Pest Plants and Animals Feral Rabbit data Our Strategy For the Future		HERBICIDE RESISTANCE Back to the Weeds Home Page Herbicides prevent or reduce weeds and thus replace or reduce manual and mechanical weeding. Manual weeding has been linked with occupational health and safety issues such as lower back and limb pain; while mechanical weeding destroys soil structure and soil flora and fauna. Because herbicides reduce the need for cultivation, herbicides can prevent soil erosion and water loss, and are widely used in conservation farming. Herbicides can be divided into two categories: Non-selective herbicides that stop the growth of all plants. Selective herbicides that are crop-specific and control weeds without harming the crop. Our heavy dependence on herbicides and the adaptability of many weeds such as ryegrass and radish has led to herbicide resistance developing in some areas. Herbicide resistance has developed a strong foothold in Australian agriculture since it was first reported in 1982 and has become a key constraint to crop production in all states. How does resistance develop? In any given population of plants there will always be number that contain genes which are resistant to herbicides and enable them to survive. Each time the same chemical is used those susceptible individuals die and the resistant plants survive. If the same herbicide is used over and over again eventually all the plants in the population are resistant. When a wider variety of control techniques and herbicides with a different mode of action are used. Herbicide resistance is less likely to develop. Resistance is not something that will suddenly appear over the whole of a property. It may occur in small areas or in one paddock. Detection of these areas will allow landholders to take action to prevent or delay spread to the whole of the property. Selection of resistant strains can occur in as little as 3 - 4 years. When planning your weed control program, you need to know the mode of action of the herbicide and what essential function does the chemical disrupt in the target plant. These two factors put herbicides together in groups to facilitate the management of herbicide resistant weeds. Using this information you can design anti resistant strategies such as checking which chemicals are in the same group, and where possible reduce reliance on high risk groups. Once a population is resistant to one herbicide in one group then it is resistant to all the others in the group. In order to manage herbicide resistance you should keep accurate records on a paddock basis. Herbicide Resistance Test The exact resistance of a plant cannot be known without testing. Knowledge of the resistant status of weeds on your property will enable you to manage your property and the threat of herbicide resistance. The Agrisearch resistant test is the most economical way to find this out. In comparison herbicide failure can be extremely costly. The test will tell you whether resistant plants are present and the degree of resistance in the population. There are five types of test available for testing of ryegrass, wild oats. silver grass and radish. Some of the tests can check for resistance to certain groups and others can be done to for any nominated registered herbicide. Seed sampling for testing is best done in spring to early summer. Results can take up to 3mths. Please pick up a herbicide resistance sampling pack from the Department of Agriculture and Food in Northam. For more detailed information about all aspects of herbicide resistance and crop protection look at The Avcare website at Avcare website Reference: Herbicide resistance a reference manual Dept of Agriculture Miscellaneous publication 16/94 Herbicide resistance and Modes of Action, Avcare 2000 pamphlet Back to the Weeds Home Page