Without intervention, the colorful but destructive Japanese beetle can cross the evergreen state within two decades, according to a study of their potential spread.
The iridescent, green-and-copper beetle damages plants by “skeletonizing” their leaves, chewing through all the tender green parts between the roots. They eat over 300 plants and pose a serious threat to Washington agriculture as some of their favorite crops include grapes, hops and cherries.
Once established, Japanese beetles are difficult to eradicate, but it is possible to control them, said David Crowder, an entomologist at Washington State University.
“These coordinated, intensive efforts early in the invasion are critical because if we wait too long, this will only become an endemic problem,” said Crowder, senior author of the study published in Journal of Economic Entomology. “Hopefully, we can prevent the beetles from spreading beyond the quarantine areas, at least for the foreseeable future.”
The study found that Japanese beetles tend to thrive in the dry, agriculturally rich southeastern part of the state, where the first individuals were found three years ago. If they escape quarantines in place in those areas, modeling shows they likely spread throughout the region from Yakima to the Tri-Cities and north across Moses Lake. While the Cascades are a barrier, there are many areas in western Washington that also have suitable habitat for Japanese beetles.
Japanese beetles have spread across much of the United States. It is believed that they first arrived on the East Coast in 1916 but have only recently reached the Western states. The first beetles found in Washington were found in a parking lot in the town of Sunnyside in 2020. Two years ago the Washington State Department of Agriculture trapped more than 20,000 in Sunnyside and Grandview. So far in 2023, trapping shows that the beetles mostly remain in those areas, although there has been one report outside of Seattle.
This evidence shows that quarantine zones can be effective, the researchers said. Quarantines provide guidelines such as ensuring that yard waste does not leave the premises and agricultural trucks are thoroughly cleaned.
While beetles can fly, people often help them reach new places.
“People can easily detect the adult Japanese beetles, but it is very difficult to detect them in the earliest stages of life, the eggs and larvae, so that people may inadvertently help their spread,” said Gengping Zhu, assistant research professor at WSU and the study’s first author.
Japanese beetles lay their eggs near the surface of the soil and spend much of their life cycle underground as larvae feeding on roots and other organic soil material. When they become beetles, they come out to eat plants. Some of their favorite plants are grapes, hops and cherries, which may partly explain their appearance first in southeastern Washington.
When they were first found in southeastern Washington, the state’s agriculture department, working with federal agencies, took the lead in setting up quarantines there. WSU scientists are joining the effort to help understand where the bugs might move next.
The effort to control the spread requires the help of the agricultural industry and residents to report where the beetles are found and take appropriate measures, Crowder said.
“Having an engaged citizenry is very important in preventing the spread of invasive species in general, even beyond the Japanese beetle,” he said. “The problems of invasive species will get worse and worse with climate change and increasing human connectivity. The more coordinated we are, and the more we can recognize the early stages of these invasions, the better.”
More information on how to identify Japanese beetles and help prevent their spread can be found at: agr.wa.gov/beetles.
Gengping Zhu et al, Potential distribution and spread of the Japanese beetle in Washington State, Journal of Economic Entomology (2023). DOI: 10.1093/jee/toad116
Provided by Washington State University
Citation: Japanese beetles could spread across Washington state within 20 years (2023, July 18) retrieved on July 18, 2023 from https://phys.org/news/2023-07-japanese-beetles -washington-state-years.html
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