The journal Weed Science reports on methods of testing for herbicide resistance. The authors of a review article discuss testing techniques, including field surveys, plant sampling, and dose-response levels. Rapid resistance confirmations are contrasted with more thorough DNA-based tests.
More than 200 plant species worldwide are resistant to herbicides. Modern agriculture depends on resistance testing to determine the best resistance management and mitigation. There are basic steps in testing, but details may vary depending on the herbicide mechanism of action, weed species, and timing of application.
The classical approach to resistance confirmation is to collect seeds from surviving plants in suspected fields, plant them in pots, and apply appropriate herbicide(s). Multiple doses are used to allow the production of a dose-response curve that will show the magnitude of resistance. The test should include three to four replications to confirm results, taking up to 2 months.
Full text of the article, “Review: Confirmation of Resistance to Herbicides and Evaluation of Resistance Levels,” Weed Science,Vol. 61, No. 1, January-March 2013