Industry perspectives on herbicide resistance monitoring and mitigation

Evolved herbicide resistance (HR) in weeds has become an important issue affecting global food production.  Early detection of HR, understanding its scope in a defined area, and potential mitigation are important aspects of managing the risk of HR.  Weed scientists have employed a variety of methods to characterize the spread of resistant weeds. Much has been learned about the design and the value of different types of HR monitoring programs.  Information obtained from monitoring can help guide farmer implementation of best management practices to mitigate resistance. Primary monitoring methods include: (1) controlled environment bioassays of putative resistant plants grown from field seed collections; (2) surveys of farmers and weed management experts; and (3) tracking farmer performance inquiries with appropriate follow up field evaluation and testing.  The most common monitoring method used by the scientific community is a field survey designed to either qualitatively (i.e. presence/absence in geographies) or quantitatively (i.e. determine the area infested with HR populations) define existing HR, while tracking farmer performance inquiries is the primary method to detect resistance in new species and in new geographies.  Once resistance has been identified, actions can be taken to limit its spread.  These mitigation measures must be designed within the context of the weed’s biology and agricultural setting where it exists. This paper examines the usefulness and limitations of various methods of monitoring along with the potential effectiveness of mitigation practices.