Understanding Genetic Differences Will Help Manage an Idaho Pest

November 23, 2020

A wireworm is the small grub-like larva of a click beetle. It’s a major pest to Idaho farmers, and poses a continually growing economic threat. Researchers at the University of Idaho and the Idaho Wheat Commission have found that two species of wireworms are actually comprised of multiple genetically distinct groups that are divergent enough to be considered unique species. They found a total of five potential species, which means that managing these pests could be even more difficult.

Kimberly Andrews, a Bioinformatics Data Scientist in IBEST’s Genomic Resources Core was lead author on a paper published in the Communications Biology journal in September; the paper outlines their genomic analysis of wireworms and the surprising discovery of multiple potential species.

One of the reasons that wireworms are such a growing threat is that the pesticides used to control them previously have been discontinued due to concerns about their negative environmental and health impacts. Farmers are now shifting their focus to Integrated Pest Management (IPM) strategies that use a combination of management approaches tailored to the biology and ecology of individual pest species and populations. However, implementation of IPM for wireworms is challenging because little is known about their species composition across the state. “You need a solid knowledge of the biology of the organisms to use IPM,” says Andrews. “There’s also an idea that different species—and even populations within species—respond differently to IPM strategies. That’s why it’s important to understand what species and populations are present across Idaho.”

Andrews says that the team was surprised when they found that two of the wireworm species were made up of several genetically distinct groups different enough to be separate species. “They’re very genetically divergent from each other. That means that they could potentially respond differently to different IPM strategies.” These groups have no known morphological differences, and therefore probably would not have been discovered were it not for genetic analysis. In addition, they discovered preliminary evidence for the presence of multiple distinct populations within species.

Another element of this project was the sequencing and assembling of the whole genome of Limonius californicus, the primary wireworm species threatening Idaho farmers. This is the first genome sequenced for a click beetle in North America—the only other click beetle species with a sequenced genome is from the Caribbean. Andrews says this genome will be a great resource for a variety of future analyses, such as “studies that look for the genomic basis underlying the response of these organisms to pesticide treatments, or studies that try to understand population dynamics and the mechanisms leading to population explosions.”

A New Resource for Farmers and Scientists


The wireworm study started in 2015 as a collaboration between IBEST and the Idaho Wheat Commission, resulting in publication of the first L. californicus mitochondrial assembly. IBEST researchers built on this initial success by organizing a working group of researchers and stakeholders from several states and Canada who agreed that developing better genomic resources for L. californicus should be a top priority. Based on this feedback, IBEST scientists developed a research proposal to continue with the genome assembly work that had already begun. Primary funding for this proposal came from the Idaho Wheat Commission, which invested in the project when Idaho wheat producers identified it as a priority. “They’re the main driving force behind all of this. They’re very interested in wireworms and their impact on Idaho farmers,” says Andrews, who got involved with the project when she began working at IBEST in April 2019. “This was the first project that I worked on when I started here,” she remembers. “The other project members had generated the sequence data, and they needed somebody to analyze it and write the paper.”

Future studies for this line of research will involve more sampling across Idaho to determine whether additional wireworm species are present, and to better understand the geographic limits of populations within species. Taxonomic experts can use the genomic information to evaluate whether morphological differences exist between the genetically distinct groups, which is central to classifying new species. In addition, the publicly available genome sequence for L. californicus will act as an important resource for future studies aimed at identifying genomic mechanisms underlying wireworm population outbreaks and responses to pest management strategies.

Another outcome of this study was preliminary evidence for genomic adaptation in a closely related pest species, L. canus, in response to changes in pesticide treatments. Andrews believes that “it would be very interesting to set up more controlled experiments to address this. It’s a fairly big task; it would probably have to take place over many years.”

The findings from this study have extensive applications in agriculture, where farmers now have the tools to better implement IPM strategies and protect their crops from a widespread pest. “Genetics provides a really big advantage for studying wireworms because you don’t need a taxonomic expert to tell them apart,” says Andrews. “There are standardized protocols that any genetics lab could use to figure out what species you have.” This research also affects genomic researchers, who can use the newly sequenced genome of L. californicus to further their own work. “A lot of people get excited about a whole genome sequence. It’s really good information to have.”

This study involved a large team of researchers from the University of Idaho, Idaho Wheat Commission, Oregon State University, Washington State University, Montana State University, and Agriculture and Agri-Food Canada. Team members included Arash Rashed from the U of I’s College of Agriculture and Life Sciences, Cathy Wilson from the Idaho Wheat Commission, the IBEST Genomics Resources Core staff, and many more.

Funding was provided by the Idaho Wheat Commission, Idaho Barley Commission, Oregon Potato Commission, NSF Idaho EPSCoR Program, National Science Foundation award number OIA-1757324.

Read the Paper



Article by Katy Riendeau
IBEST Design & Marketing Coordinator