If the answer to any of these questions is yes and all other factors have been ruled out, then resistance should be strongly suspected. A sample of the whole plant or seed should be collected and sent to an appropriate laboratory according to the instructions of the herbicide manufacturer. Accurate and reliable resistance confirmation testing procedures have to be applied. The following guidelines cover instructions for confirmation testing, seed sampling, trial design, interpretation of results and handling of resistant plants and seeds. For the triazines and ureas, other methods are also available.
All methods require a certain amount of time.
Seeds should be collected from mature surviving treated plants and packed in paper bags for storage and transportation to an appropriate laboratory to carry out the confirmation bioassay. As an alternative, whole plants could also be collected in the field and brought to maturity in the greenhouse. Other important remarks To ensure that the seed sample is representative of the population, the seed should ideally be taken from a minimum of 40 plants and bulked to reach a minimum of 1000 seeds. It is essential to also obtain seeds from susceptible biotypes as a reference for confirmation testing. These seeds should be collected from plants in the same region where the suspected resistant plants are growing, but where no herbicides have been applied.