New study sheds light on how Colorado potato beetles rapidly evolve resistance to insecticides

Insecticide resistance and rapid pest evolution threatens food security and the development of sustainable agricultural practices, yet the evolutionary mechanisms that allow pests to rapidly adapt to control tactics is unclear. The Colorado potato beetle (Leptinotarsa decemlineata) has evolved resistance to over 50 different insecticides, making the insect a super-pest that wreaks havoc on potatoes around the world. In new research, a team of U.S. scientists analyzed whole-genome resequencing and transcriptomic data sets of the Colorado potato beetle focused on the ancestral and pest ranges of this global super-pest in North America.

Herbivorous pests cause an estimated 18-20% damage to crops and cost nearly $470 billion annually on a global scale.

The ability of insect pests to evolve resistance to insecticides threatens food security and the development of sustainable agricultural practices, especially when their rate of evolution outstrips the development of novel control strategies.

This is the case with insect ‘super-pests,’ which repeatedly evolve insecticide resistance even as they are faced with completely novel insecticides, thus perpetuating the arms race that defines the pesticide treadmill.

The Colorado potato beetle is a global super-pest and an especially tractable example of rapid evolution to insecticides.

This super-pest has evolved resistance to over 50 different insecticides in all the major classes, in some cases within the first year of use.

This species has demonstrated an ability to rapidly evolve in response to a wide range of environmental pressures, including host-plant defenses and climatic variability.

The Colorado potato beetle originated in the Great Plains region of the United States, following a host shift to potato — an introduced crop — in the mid-19th century (around 1859) that allowed for rapid spatial expansion from Nebraska to the Eastern U.S. in a 20-year period and colonization of Eurasia by the early 1900s.

Despite rapid expansion, populations are genetically differentiated and insecticide resistance is geographically heterogeneous, even over local landscape scales.

In particular, beetles from Long Island, New York are known to have the highest levels of baseline resistance and are typically the first populations to develop resistance to all compounds, whereas populations in the Pacific Northwest remain susceptible to insecticides despite an equivalent duration of usage and comparable treatment practices.

Nonpest populations are native to the Great Plains and Mexico, where they use ancestral host plants, primarily Solanum rostratum.

“This beetle was one of the first to be attacked with chemicals in the modern era, and it’s been very successful at evolving past those attacks,” said senior author Professor Sean Schoville, a researcher in the Department of Entomology at the University of Wisconsin-Madison.

“For other insects we’re hoping to control, there’s lessons to be learned from studying this pest. What mechanisms does this insect use to get past these insecticides?”

Professor Schoville and colleagues first sequenced the genome of the Colorado potato beetle in 2018.

In the new study, they compared genomic and transcriptomic variation across populations of the Colorado potato beetle in the United States, Mexico, and Europe, as well as nine closely related species in the Leptinotarsa genus.

They discovered that these different regional groups evolved so quickly because their parent populations already had the genetic resources necessary to overcome insecticides.

“The genes that evolve are well known to be involved in insect resistance,” Professor Schoville said.

“But what’s interesting is that different populations are altering different parts of genes or different genes in the same pathway.”

“This similar, but not identical, pathway to resistance across different populations is known as repeated evolution.”

“This rapid evolution based on a wealth of existing genetic diversity is at odds with an older model of evolution that assumed rare mutations have to slowly arise in a population,” he said.

“While new mutations do develop and can contribute to insecticide resistance, the potato beetle’s rapid response to new chemicals in different parts of the country can be explained only by its existing diversity.”

The results were published in the journal Molecular Biology and Evolution.

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Benjamin Pélissié et al. 2022. Genome Resequencing Reveals Rapid, Repeated Evolution in the Colorado Potato Beetle. Molecular Biology and Evolution 39 (2); doi: 10.1093/molbev/msac016