According to Gram Research analysis, western corn rootworms can develop resistance to two new experimental insecticidal proteins within 10 generations of repeated exposure. In laboratory studies, rootworms bred on corn expressing Mpp75Aa1.1 achieved a 5-fold resistance advantage, while those bred on Vpb4Da2 showed nearly complete resistance with zero mortality at any tested concentration. This research demonstrates that these new pest-control tools will eventually face the same resistance problems that have already affected all five currently used Bt proteins, making proactive resistance management strategies essential before widespread commercial adoption.
Scientists at Gram Research analysis have discovered that western corn rootworms, a major agricultural pest, can develop resistance to two new experimental proteins designed to kill them. Researchers bred rootworms in the lab over multiple generations on corn plants containing these proteins to see how quickly resistance could develop. They found that the insects adapted to both proteins, though at different speeds and with varying levels of resistance. This research helps farmers and scientists prepare for potential problems before these new pest-control tools are widely used in cornfields across America.
Key Statistics
A 2026 research article in PLoS ONE found that western corn rootworms developed resistance to Mpp75Aa1.1 within 13 generations of laboratory selection, achieving a resistance ratio of 5 compared to normal insects.
According to a 2026 study of laboratory-selected western corn rootworms, insects bred on Vpb4Da2-expressing corn showed complete resistance with zero mortality on artificial diet containing the protein, indicating extremely high resistance levels.
Research published in 2026 demonstrated that resistance to both new insecticidal proteins showed effective dominance values below 0.25, meaning resistance is recessive and will spread more slowly than dominant resistance traits in wild populations.
A 2026 laboratory study confirmed that western corn rootworms have already developed resistance to all five Bt proteins currently used commercially in the United States, leaving only DvSnf7 dsRNA as an active tool without reported field resistance.
The Quick Take
- What they studied: Whether western corn rootworms could develop resistance to two new insecticidal proteins (Mpp75Aa1.1 and Vpb4Da2) that scientists are considering using in genetically modified corn crops.
- Who participated: Laboratory colonies of western corn rootworms that were selectively bred over 13 to 14 generations on corn plants expressing either Mpp75Aa1.1 or Vpb4Da2 proteins to simulate how resistance might develop in nature.
- Key finding: Both rootworm colonies successfully developed resistance to their respective proteins. The Mpp75Aa1.1-resistant insects showed moderate resistance with a 5-fold survival advantage, while Vpb4Da2-resistant insects showed very high resistance with nearly complete survival on treated corn.
- What it means for you: Farmers should know that these new pest-control tools may eventually face resistance problems, just like older insecticides have. This research helps scientists plan better strategies now, such as rotating different proteins or combining them, to keep these tools effective for longer.
The Research Details
Scientists created two separate colonies of western corn rootworms in the laboratory. They repeatedly exposed each colony to corn plants expressing one of the two new insecticidal proteins over 13 to 14 generations. This process mimics what happens in nature when insects are repeatedly exposed to the same pest-control tool. The researchers then tested whether the surviving insects had actually become resistant by measuring how many survived and developed into adult beetles on treated corn compared to regular corn. They also tested the insects on artificial diets containing the proteins to understand exactly how resistant they had become.
This controlled laboratory approach allows scientists to predict what might happen in real cornfields before these new proteins are widely adopted. By understanding how quickly and completely resistance can develop, farmers and agricultural companies can plan better management strategies now, such as using multiple different proteins in rotation or combining them together. This proactive approach prevents the costly problem of having a pest-control tool fail after farmers have invested in it.
The study used standard scientific methods including multiple generations of selection, controlled bioassays (laboratory tests), and statistical analysis to estimate resistance levels. The researchers confirmed resistance through two different testing methods: on actual transgenic corn plants and on artificial diet, which strengthens their conclusions. The study was published in PLoS ONE, a peer-reviewed scientific journal. However, the study was conducted in controlled laboratory conditions, so real-world resistance development in actual cornfields may differ based on factors like weather, soil, and farming practices.
What the Results Show
Both rootworm colonies successfully developed resistance to their respective proteins after 10 generations of selection. The Mpp75Aa1.1-resistant insects showed a resistance ratio of 5, meaning they could survive at concentrations that would kill normal insects. These resistant insects survived equally well on both treated corn and regular corn, confirming true resistance. The Vpb4Da2-resistant insects showed even stronger resistance, with no measurable mortality at any concentration tested on artificial diet. These insects also survived equally well on both treated and untreated corn plants. Both resistant colonies showed what scientists call semidominant to incompletely recessive resistance patterns, meaning that when resistant insects bred with normal insects, the offspring showed intermediate resistance levels rather than full resistance.
The study measured effective dominance values for both resistant colonies. For Mpp75Aa1.1-resistant insects, the effective dominance was 0.23, and for Vpb4Da2-resistant insects, it was 0.24. These low values indicate that resistance is recessive, meaning an insect needs to inherit resistance genes from both parents to show strong resistance. This is actually good news for resistance management, as it suggests resistance will spread more slowly in wild populations compared to dominant resistance traits. The concentration response testing showed that Mpp75Aa1.1-resistant insects still showed some dose-dependent effects, while Vpb4Da2-resistant insects showed no response to increasing concentrations.
This research builds on a concerning trend in corn pest management. Western corn rootworms have already developed resistance to all five Bt proteins currently used commercially in the United States. The only currently available tool without reported field resistance is DvSnf7 dsRNA, a newer technology. This study suggests that the two new proteins being tested (Mpp75Aa1.1 and Vpb4Da2) will eventually face similar resistance problems if deployed without proper management strategies. The research emphasizes that resistance is not a matter of if but when, making proactive planning essential.
This study was conducted entirely in controlled laboratory conditions, which may not perfectly reflect what happens in real cornfields. Real-world factors like weather, soil conditions, crop rotation, and the presence of non-resistant insects in surrounding areas could affect how quickly resistance develops. The study used artificial selection pressure by exposing insects to the proteins every generation, which may be more intense than what occurs naturally. Additionally, the study did not examine whether resistance to one protein might affect resistance to the other or to other pest-control tools. The exact mechanisms of how the insects became resistant were not fully investigated.
The Bottom Line
Farmers should prepare for the eventual development of resistance to these new proteins by planning integrated pest management strategies now. This includes rotating different insecticidal proteins, combining multiple proteins in the same plants, maintaining refuges of non-treated corn to keep susceptible insects in the population, and monitoring fields for signs of resistance. These strategies have proven effective at slowing resistance development to other pest-control tools. The confidence in these recommendations is high based on decades of experience with resistance management in agriculture.
Corn farmers in the Midwestern United States should pay close attention to this research, as western corn rootworms cause billions of dollars in damage annually. Agricultural scientists, seed companies, and pesticide manufacturers need this information to develop better resistance management plans. Policymakers should consider requiring resistance management strategies before approving new pest-control proteins for widespread use. This research is less relevant to consumers in other regions or those growing different crops, though it demonstrates broader principles about pest resistance that apply across agriculture.
Based on this laboratory study, resistance could potentially develop within 10 to 15 years of widespread commercial use if no resistance management strategies are implemented. However, real-world resistance development could be faster or slower depending on farming practices and environmental factors. Farmers should begin implementing resistance management strategies immediately upon adoption of these new proteins, rather than waiting for resistance to appear in their fields.
Frequently Asked Questions
Can corn rootworms develop resistance to new insect-killing proteins?
Yes, research shows western corn rootworms can develop resistance to new insecticidal proteins within 10 to 15 generations of exposure. A 2026 study found that laboratory-selected rootworms achieved 5-fold resistance to Mpp75Aa1.1 and nearly complete resistance to Vpb4Da2, demonstrating this is a real concern for farmers.
How quickly do corn rootworms become resistant to pest control?
Laboratory studies show resistance can develop within 10 to 14 generations of repeated exposure. In real cornfields, this could translate to 5 to 10 years depending on farming practices and how widely the pest-control tool is used. Resistance management strategies can significantly slow this process.
What should farmers do to prevent corn rootworm resistance?
Farmers should rotate different insecticidal proteins year to year, combine multiple proteins in the same plants, maintain refuges of non-treated corn, and monitor fields regularly for pest populations. These integrated strategies have proven effective at delaying resistance development to other pest-control tools.
Are the new insecticidal proteins Mpp75Aa1.1 and Vpb4Da2 still worth using?
Yes, these proteins remain valuable tools when used with proper resistance management strategies. They offer alternatives to existing Bt proteins that rootworms have already resisted. Rotating between different proteins and combining management approaches can keep these tools effective for many years.
Why is this laboratory study important for real-world farming?
Laboratory resistance studies predict what might happen in actual cornfields, allowing farmers and companies to plan better management strategies before resistance appears. This proactive approach prevents costly failures of pest-control tools and protects agricultural productivity.
Want to Apply This Research?
- Track which insecticidal proteins or corn varieties you plant in each field each year, noting the date of planting and any observed pest damage or survival. This creates a record that helps identify early signs of resistance development, such as increasing rootworm populations despite using treated corn.
- Set a yearly reminder to rotate your corn pest-control strategy. If you used Mpp75Aa1.1-expressing corn this year, plan to use a different protein or management approach next year. Document this plan in the app before planting season to ensure you follow through.
- Establish a long-term monitoring system by scouting your cornfields regularly during the growing season and recording rootworm populations. Compare populations in fields using different pest-control strategies to detect any changes in effectiveness over time. Share this data with your local agricultural extension office to contribute to regional resistance monitoring efforts.
This research describes laboratory studies of insect resistance and does not constitute agricultural advice. Farmers should consult with local agricultural extension services, agronomists, and seed company representatives before making decisions about which corn varieties or pest management strategies to use. Resistance management recommendations should be tailored to local conditions, pest populations, and farming practices. This article is for informational purposes only and should not replace professional agricultural guidance.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.