By TYLER ELLYSON
UNK Communications
KEARNEY – U.S. farmers harvested 41 billion pounds of potatoes last year.
Worth an estimated $4.06 billion, it’s a big industry that continues to battle a tiny insect.
The Colorado potato beetle is a major problem for producers throughout North America and around the world. This insect devours the leaves of potato plants, causing damage that can lead to significant yield loss.
Although it’s been around for decades – the first outbreak was observed in Nebraska in the 1850s – farmers have yet to figure out how to control this so-called “super pest.”
“It’s a large issue, and it’s been that way since the mid-19th century,” said Benjamin Pélissié, an assistant biology professor at the University of Nebraska at Kearney.
The Colorado potato beetle was “one of the main drivers of the development of pesticides in the modern era,” according to Pélissié, and it’s also notorious for its ability to rapidly adapt to these chemicals. The beetle has developed resistance to more than 50 different insecticides in all major classes, in some cases within the first year of use.
“It’s basically resistant to whatever pesticide you throw at it,” said Pélissié, who started studying the beetle in 2016 as part of a postdoctoral project at the University of Wisconsin-Madison, where he worked in entomology professor Sean Schoville’s lab.
Schoville first sequenced the beetle’s genome in 2018, and he and Pélissié have been collaborating since then to better understand how the insect can overcome new pesticides so quickly.
Led by Schoville, the research team studied dozens of potato beetles from populations across the U.S., allowing them to identify genetic signatures of pesticide adaptations specific to certain regions. Their findings, published earlier this year in the journal Molecular Biology and Evolution, show the beetle’s high level of genetic diversity allows some of its populations to recruit mutations that are already present in their gene pools and quickly evolve resistance to new compounds.
“The level of genetic variability is so high that they’re almost preadapted to whatever is going to happen to them,” Pélissié explained. “They’re so diverse that whatever we throw at them, the mutation is going to be there somewhere in the population.”
Known as repeated evolution, populations respond to chemical treatments by selecting either different mutations of the same genes or different genes within the same genomic pathways, depending on their genetic makeup and the particular pesticide pressure they are facing locally. This counters a previous belief that mutations involved in pesticide resistance were rare and had to spread among populations, over a longer period of time and many generations.
“That’s very important, because for growers, it kind of changes the game,” said Pélissié, who joined the UNK faculty in January 2020.
Given the insect’s genetic makeup, it’s unlikely that even a brand-new pesticide would have long-term effectiveness against the Colorado potato beetle. However, this knowledge could help researchers design better management tactics that keep it in check.
“We can’t just count on one mechanism of management,” Pélissié said. “There are different strategies that can be employed, and one of them has been around for a while now.”
Integrated pest management utilizes a combination of approaches to limit crop damage. For the potato beetle, this could include tillage and other land-management practices, crop rotation and planting adjustments based on the insect’s life cycle and activity levels.
In Nebraska, the potato beetle is still present, but its populations are largely controlled by predatory wasps and other natural factors.
“It’s not a major issue here and it’s not resistant to pesticides because it’s not under heavy pressure from pesticides,” Pélissié said. “That’s very different from other parts of the country where the pressure is very high.”
Pélissié is also digging into the history of the Colorado potato beetle, which likely shifted to potatoes from a different host plant in the same nightshade family – buffalo bur.
“That’s a plant that we believe was brought from Mexico with the settlers moving north between the 16th and 19th centuries,” he said.
The noxious weed is commonly found in pastures, rangeland and other areas throughout the Great Plains. Because it’s toxic to livestock, Pélissié wants to know whether the potato beetle’s ability to feed on this plant facilitated the repeated evolution of its resistance to artificial chemicals.
“We need to keep looking ahead and push forward this fundamental knowledge of how resistance evolves in the field, because that’s the only way we can develop new solutions to this ongoing problem,” he said. “And that applies to any pest, really.”
