LAWRENCE, Kan. — An article in the current issue of Weed Science sets out industry views on how herbicide resistance should be monitored and mitigated.
The article, authored by independent scientist John Soteres and Dow Agro-Sciences Global Product Development Leader Mark Peterson, provides a summary of the issues around resistance that appears in longer form on the website of the Herbicide Resistance Action Committee (HRAC).
This is an industry-supported group backed by eight major companies working as part of Crop Life International.
"While resistant weeds have been with us ever since people started picking weeds out of rice fields thousands of years ago, there certainly has been significant public discussion about herbicide resistance," Peterson said in an interview. "Given some proposals for more detailed monitoring of resistance, HRAC felt it important that a factual discussion of the topic be made available to the public and policymakers.
"The paper represents a review of various means by which we can get a better understanding of herbicide resistance, but also points out the scientific and practical limitations of these methods."
Major points in the article include the assertion that one shouldn’t think of resistance eradication as a feasible goal in most instances.
First of all, farmers tend to exaggerate the extent and incidence of it, the authors say, often blaming what are really other source problems on resistance. Farmers pass on their complaints to the herbicide retailers, who may then relate the complaints to the manufacturers.
Records of these performance inquiries have been used to assess the extent of resistance, but this and other "qualitative" methods are not especially reliable in determining the extent of herbicide resistance, they say. This problem complicates any efforts at effective monitoring.
According to the paper, while it is fairly easy to monitor for insect resistance because of the relatively widespread movement of those pests, this is not the case for herbicide-resistant weeds.
Scientists and extension specialists can set up field traps to collect insects in a given area and thereby monitor for resistance that way.
This option is unavailable to those wanting to monitor for herbicide resistance.
Monitoring for it is possible, but it’s really a "hit and miss" proposition if the resistance is not already advanced.
Moreover, the authors say insects and fungi reproduce relatively quickly and thus it is easier in both instances to tell if individuals are becoming resistant to treatment, than it is with weeds. They also point out a weed can have numerous types, even in the same area – and this complicates monitoring further.
"Resistance monitoring processes for weeds are fundamentally different from those for insects or diseases," the authors write. "Methods such as baseline monitoring that are used for these other pests are not readily transferable to weeds.
"Although monitoring programs for insecticide and fungicide resistance may offer some concepts that can be applied to herbicide resistance, basic biological differences among the taxa will drive very different approaches."
Monitoring and discovering herbicide resistance would be expensive and sometimes impossible in the early stages of weed resistance, the authors say. Once it is advanced, however, mitigation becomes more difficult too. According to the authors, the remedy is faster – and better – communication.
Faster communication of confirmed resistance to farmers may help them implement best management practices, the authors say.
More timely communication across the technical community would also help experts be more vigilant about impending resistance.
The authors invite people to read a more detailed discussion of the issue on the HRAC website at http://bit.ly/1M8DEB3
The full text of the article is available online at http://wssajournals.org – click on "Current Issue" under the Weed Science heading, then go to the bottom of the page under "Special Topics."
