Tracing the Origins of the Colorado Potato Beetle

A UMD researcher has traced the origin of pest populations of the Colorado potato beetle, by far the most important insect for the potato industry in Maryland, back to the Plains states, dispelling theories that the beetle came from Mexican or other divergent populations. Little was previously known about the beetle’s origin as a pest, particularly how it developed the ability to consume potatoes and decimate entire fields so quickly. With its unique ability to adapt to pesticides almost faster than the industry can keep up, this beetle is consistently an issue for potato farmers. Using investigative evolutionary biology to determine the origins of this beetle and understand the pest’s genetic makeup better, industry can better target pest management strategies to combat pesticide resistance and ultimately improve the potato industry.

The United States is the fourth largest producer of potatoes worldwide, producing over 20 million tons of potatoes each year. By comparing the genetics of pre-agriculture potato beetles, before the pest began to consume potatoes, to post-agriculture potato beetles, Dr. David Hawthorne of the Entomology Department and his team hope to understand why and how the beetle is developing resistance so quickly, and what can be done to slow resistance. “The Colorado potato beetle is almost always one of the first insects to develop resistance to any pesticide. In fact, many contribute the entire pesticide arms race and development of pesticides to this particular beetle, which can destroy entire fields very easily,” says Hawthorne.

“With this study,” explains Hawthorne, “we were trying to gain insight into two major questions: Where did the potato beetle come from? And why do they evolve resistance so quickly? This would have major implications in controlling the pest, since the more growers have to spray, the greater their costs and risk to the surrounding environment. We need a strategy to weigh our options and determine the best way to control these pests without overspraying or even torching entire fields overrun with beetles, which has happened in the past when there has been no effective pesticide options.”

Hawthorne and his team found that populations of beetles eating potatoes are most closely related to nightshade eaters in the Plains states. Beetles from Mexico, a possible source of the pest populations, were far too distantly related to have been the source of this beetles. “Before they became pests, the plains beetles first evolved a taste for potatoes,” says Hawthorne. “Some non-pest populations still don’t eat them and will prefer the weeds surrounding the potatoes, but not the potatoes themselves. This is just one way that populations may differ.” By understanding the distinctions between these populations and which beetles are the source of current pest populations, more targeted pest management strategies can be developed based on the specific genetic makeup of the beetles, leading to more effective and less spraying.

Hawthorne describes this work as almost forensic biology, tracking the evolution and movement of this beetle across time and geography. “I like that this work is very interdisciplinary,” says Dr. Hawthorne. “It is about taking all the puzzle pieces and trying to put the whole story together to have the biggest impact on the field. Ultimately, this work is a major step towards understanding one of the most harmful pests, and has significant implications in controlling the population, keeping the potato industry stable, and fighting pesticide resistance and overspraying.”

Dr. Hawthorne’s study was published in The Journal of Economic Entomology and can be found here.

Image by Anton Vakulenko, Flickr Commons, Image license