How Scientists Are Discovering New Targets for Herbicide Resistance
Imagine a farmer facing a field overrun with weeds that refuse to die despite repeated herbicide treatments. This isn't science fiction—it's the growing reality of herbicide resistance that threatens global food security. Weeds have evolved mechanisms to survive chemicals that once controlled them, creating what scientists call a "superweed" crisis. With up to 40% of crop yields potentially lost to weed interference without effective herbicides, researchers are racing against time to discover new herbicide targets and combat this agricultural challenge 1 .
The last truly novel herbicide mode of action was introduced in the 1980s, with only two new modes of action added to the Herbicide Resistance Action Committee classification system since then 1 .
This article explores the cutting-edge science behind discovering new herbicide targets, the innovative technologies driving this research, and how these discoveries may revolutionize weed management in agriculture.
Genetic mutations alter the specific protein that the herbicide targets, preventing the chemical from binding effectively.
Plants develop enhanced abilities to detoxify herbicides through metabolic processes or prevent herbicides from reaching their targets.
The challenge of herbicide resistance has grown dramatically in recent decades. The Herbicide Resistance Action Committee (HRAC) maintains a comprehensive collection of information on weed resistance globally, documenting the alarming spread of resistant weed species 2 . Farmers face weeds resistant to multiple herbicide sites of action, complicating management efforts and increasing production costs.
In response to the growing resistance crisis, a multistate research project known as the Herbicide Resistance Monitoring Network was established. Led by researchers at Michigan State University and supported by a $500,000 grant from the United Soybean Board, this initiative brings together scientists from multiple institutions 3 .
"There is a lot about herbicide resistance that we don't know, in terms of how the weeds changed genetically or physiologically to be able to now survive a super lethal agent."
The project aims to develop rapid diagnostic tools for identifying herbicide-resistant weeds in soybean fields. Traditional methods can take months, forcing farmers to wait until the following growing season to adjust their strategies. The research team is working to reduce this timeline from months to hours or even minutes.
After decades of limited discoveries, researchers are finally identifying new herbicide targets. Two significant new modes of action have recently been classified:
Represented by the herbicide cyclopyrimorate
Represented by the herbicide tetflupyrolimet (Keenali) 1
| Product Name | Active Ingredients | HRAC Group | Target Crops | Application Timing |
|---|---|---|---|---|
| Zalo | quizalofop-P-ethyl + glufosinate ammonium | 1 + 10 | Glufosinate-resistant soybeans and canola | Postemergence |
| Surtain | saflufenacil + pyroxasulfone | 14 + 15 | Field corn | Preemergence/Early Postemergence |
| Liberty Ultra | L-glufosinate | 10 | Glufosinate-resistant soybeans and corn | Postemergence |
| Convintro | diflufenican | 12 | Corn and soybeans | Preemergence |
| Keenali | tetflupyrolimet | 28 | Rice | Preemergence/Early Postemergence |
Source: 5
| Weed Species | Common Name | Resistant to HRAC Groups | States with Documented Resistance |
|---|---|---|---|
| Amaranthus tuberculatus | Waterhemp | 2, 5, 9, 14, 27 | 12+ |
| Ambrosia artemisiifolia | Common ragweed | 2, 9, 14 | 8+ |
| Kochia scoparia | Kochia | 2, 4, 5, 9 | 10+ |
| Lolium perenne | Italian ryegrass | 1, 2, 3, 9, 22 | 5+ |
Weed science researchers utilize a sophisticated array of tools and technologies to study herbicide resistance and discover new targets. Here are some of the key reagents and materials used in this critical work:
| Reagent/Technology | Function | Application in Research |
|---|---|---|
| Transcriptome sequencing | Analyzes genetic code and gene expression | Identifying genes associated with resistance mechanisms |
| GFP-tagged proteins | Visualize protein localization and function | Studying herbicide target sites in plants |
| Herbicide-resistant mutant lines | Provide controlled research specimens | Understanding resistance mechanisms |
| High-throughput screening systems | Rapid testing of compound efficacy | Identifying new herbicidal actives |
| Molecular docking software | Predicts herbicide-target interactions | Designing herbicides for specific binding sites |
| LC-MS/MS systems | Precise chemical analysis | Measuring herbicide concentrations in plant tissues |
Source: 3
Model molecular interactions and predict herbicidal activity
CRISPR tools help validate potential herbicide targets
AI analyzes chemical libraries to identify herbicidal compounds
Monitor plant growth and response to treatments automatically
Artificial intelligence is revolutionizing herbicide discovery by predicting herbicidal activity and identifying novel target sites. Companies are using AI platforms to screen millions of molecules virtually, significantly reducing the time and cost required for discovery .
Microbial bioherbicides and natural product-based herbicides represent a growing area of research. New approaches focusing on the soil microbiome and bacterial pathogens show promise for providing additional tools for integrated weed management .
Rather than developing new herbicides, some companies are using gene editing technologies like CRISPR to develop non-GMO, herbicide-resistant crops. This approach would allow farmers to use existing herbicides on previously susceptible crops .
The battle against herbicide-resistant weeds is ongoing, but scientific advances are providing new hope for farmers struggling with increasingly resilient weeds. From rapid diagnostic tools that identify resistance in hours instead of months to novel herbicide modes of action that attack weeds in completely new ways, researchers are expanding our understanding of plant physiology and evolution.
"The 2024 growing season was a great year for waterhemp, highlighting the persistent challenge of resistant weeds."
As research continues to unveil the secret life of weeds and their defense mechanisms, scientists can develop more targeted and sustainable solutions to protect crop yields and ensure global food security.
| Decade | New Modes of Action Discovered | Representative Herbicides |
|---|---|---|
| 1940s | 2 | 2,4-D, MCPA |
| 1950s | 5 | Atrazine, Diuron |
| 1960s | 7 | Paraquat, Trifluralin |
| 1970s | 9 | Glyphosate, Metsulfuron-methyl |
| 1980s | 4 | Oxadiazon, Diclofop-methyl |
| 1990s | 2 | Isoxaflutole, Mesotrione |
| 2000s | 1 | Pinoxaden |
| 2010s | 1 | Cyclopyrimorate |
| 2020s | 1+ | Tetflupyrolimet |
Source:
The future of herbicide discovery looks brighter as interdisciplinary approaches combining genetics, biochemistry, computational biology, and ecology provide new insights into weed biology and reveal novel targets for chemical control. With continued investment in research and development, the scientific community can help farmers stay one step ahead of evolving weeds and ensure sustainable crop production for generations to come.