As cases of resistance to herbicides escalate worldwide, there is increasing
demand from growers to test for weed resistance and learn how to manage it.
Scientists have developed resistance-testing protocols for numerous
herbicides and weed species. Growers need immediate answers and scientists
are faced with the daunting task of testing an increasingly large number of
samples across a variety of species and herbicides. Quick tests have been,
and continue to be, developed to address this need, although classical tests
are still the norm. Newer methods involve molecular techniques. Whereas the
classical whole-plant assay tests for resistance regardless of the
mechanism, many quick tests are limited by specificity to an herbicide, mode
of action, or mechanism of resistance. Advancing knowledge in weed biology
and genomics allows for refinements in sampling and testing protocols. Thus,
approaches in resistance testing continue to diversify, which can confound
the less experienced. We aim to help weed science practitioners resolve
questions pertaining to the testing of herbicide resistance, starting with
field surveys and sampling methods, herbicide screening methods, data
analysis, and, finally, interpretation. More specifically, this article
discusses approaches for sampling plants for resistance confirmation assays,
provides brief overviews on the biological and statistical basis for
designing and analyzing dose–response tests, and discusses alternative
procedures for rapid resistance confirmation, including molecular-based
assays. Resistance confirmation procedures often need to be slightly
modified to suit a specific situation; thus, the general requirements as
well as pros and cons of quick assays and DNA-based assays are contrasted.
Ultimately, weed resistance testing research, as well as resistance
management decisions arising from research, needs to be practical, feasible,
and grounded in science-based methods.