A UNK researcher studies the tiny insect and its genetic superpower

Tyler Ellison, UNK Communications

Kearney – US farmers harvested 41 billion pounds of potatoes last year.

Valued at $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 a significant loss of the crop.

Although it’s been around for decades—the first outbreak of the virus was noted in Nebraska in the 1850s—farmers have yet to figure out how to control the so-called “super pest.”

“It’s a big issue, and it’s been like that since the mid-1800s,” said Benjamin Pelisset, associate professor of biology at the University of Nebraska at Kearney.

The Colorado potato beetle has been “one of the major drivers of pesticide development in the modern era,” according to Pelicier, and it’s also famous for its ability to adapt quickly 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.

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“It’s basically resistant to whatever insecticide you throw at it,” said Pélissié, who began studying the beetle in 2016 as part of a postdoctoral project at the University of Wisconsin-Madison, where he worked in the lab of entomology professor Sean Scoville.

Schoville first sequenced the beetle’s genome in 2018, and he and Pélissié have since been collaborating to better understand how the beetle is able to outcompete new pesticides so quickly.

The research team led by Schoville studied dozens of potato beetles from populations across the United States, allowing them to identify genetic signatures of region-specific pesticide adaptations. Their findings, published earlier this year in the journal Molecular Biology and Evolution, show that the beetle’s high level of genetic diversity allows some of its population to recruit mutations already present in their gene pools and rapidly develop resistance to new compounds.

“The level of genetic variance is so high that she has adapted almost everything that will happen to her,” Pelissier explained. “They are so diverse that whatever we throw at them, the mutation is going to be there somewhere in the population.”

Known as iterative evolution, populations respond to chemotherapies by selecting different mutations of the same genes or different genes within the same genetic pathways, depending on their genetic makeup and the particular pesticide pressure they encounter locally. This conflicts with a previous belief that mutations involved in pesticide resistance were rare and should spread in populations, over a longer period of time and many generations.

“This is very important, because for farmers, it’s kind of changing the game,” said Pelissé, who joined the faculty at UNK in January 2020.

Given the insect’s genetic makeup, it is unlikely that an entirely new pesticide would have long-term efficacy against the Colorado potato beetle. However, this knowledge can help researchers design better management techniques that keep them in check.

“We cannot rely on a single management mechanism,” said Plessier. “There are different strategies that can be used, and one of them has been around for a while.”

Integrated pest management uses a range of methods to reduce crop damage. For the potato beetle, this can include plowing and other land management practices, crop rotations and planting modifications based on the insect’s life cycle and activity levels.

In Nebraska, the potato beetle is still found, but its numbers are largely controlled by predatory wasps and other natural factors.

“It’s not a major problem here and it’s not resistant to pesticides because it doesn’t come under severe pesticide stress,” Pelissier said. “This is very different from other parts of the country where the pressure is very high.”

Pélissié is also researching the history of the Colorado potato beetle, which likely morphed into potatoes from a different host plant in the same nightshade family – the buffalo bur.

“This is a plant that we think was brought from Mexico as settlers moved north between the 16th and 19th centuries,” he said.

Weeds are commonly found in pastures, pastures, and other areas throughout the Great Plains. Since it is toxic to livestock, Pélissié wants to know if the potato beetle’s ability to feed on this plant has facilitated the repeated evolution of its resistance to synthetic chemicals.

“We need to keep looking forward and advancing this basic knowledge of how resistance is evolving in the field, because that is the only way we can develop new solutions to this ongoing problem,” he said. “And that goes for any pest, really.”

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