New research shows how emphasizing collaboration and local knowledge in China can advance preparation for responding to invasive insects that could threaten North American tree species. Native to eastern Asia, the citrus longhorned beetle (Anoplophora chinensis) is one such species noted in the study, noted for its capacity to infest and kill live pecan trees (Carya illinoinensis). (Photo by Taiwan Waterbird Research Group, Changhua Coastal Conservation Action Alliance on Flickr, CC BY-NC-SA 2.0)

By Carolyn Bernhardt

Previous research has shown that, between 2003 and 2012, insect pests affected more than 85 million hectares of forest worldwide, much of which was in temperate North America. Invasive insects tear through North American forest systems at such an alarming rate that the U.S. Department of Agriculture announced in January that it would spend over $70 million on beefing up pest detection, surveillance, and control systems and safeguarding the U.S. nursery system in 2023. The funding supports 350 projects led by universities, states, federal agencies, non-governmental organizations, nonprofits, and Tribal organizations across 48 states, Guam, and Puerto Rico.

And, for all the researchers working to prevent the spread of invasive pests and minimize their impact, studies that help anticipate and prepare for the arrival of invasives are just as crucial as conducting research that informs response measures.

“Routinely, when an invasive pest shows up, the authorities perform a mad scramble, pour money on it, and [direct scientists] to do monitoring, assessment, and delineation,” says Jiri Hulcr, Ph.D., an associate professor with the School of Forest, Fisheries, and Geomatic Sciences and the Department of Entomology and Nematology at the University of Florida. The approach, he says, only works with some pests. “In most cases, we find out about the bug months—if not years—after it has already killed thousands of trees.” So, he and his team want to “get ahead of that curve.”

For the past decade, Hulcr and his team have been committed to regrowing relationships across academics in China and the U.S. to better understand and, eventually, prevent the spread of invasive pests in both nations. But, despite a significant trade relationship, tension has mushroomed between China and the United States in recent years. And unfortunately, that very trade relationship helps drive the spread of invasive species in both countries.

“I can tell you, China is receiving an equal amount of pests from us,” Hulcr says. “The biggest source of invasive species is trade with live plants and trade supported by wood products, like pallets. So, it’s not these ‘evil beetles’ against us. It’s us all buying stuff at an unprecedented rate.”

In April, Hulcr and colleagues Yiyi Dong at UF and Jie Gao, Ph.D., at the Chinese Academy of Sciences published a meta-analysis in Environmental Entomology that combed both peer-reviewed and non-peer-reviewed literature published in China that reported on how insect species considered invasive in the U.S. interact with seven important North American commercial tree species planted in China.

The non-peer-reviewed literature that’s published in China, also called “grey literature,” was crucial to the project, according to Huclr. “Everyone can do a full-text search on Google in English, but this grey data published in Chinese remain inaccessible to us in the U.S.,” he says. “We are picking the brains of thousands of people by studying the gray literature.”

He also thinks the study helps fill gaps when resources aren’t available. “Lots of people are advising wisely to work with botanical gardens in China because they are already planting these ‘exotic’ North American trees, and we could potentially observe wood borers on that,” he says. But botanical garden managers use heavy pesticide spray and rarely analyze dead trees for pests before removing them. Instead, Hulcr and his team focused their meta-analysis on places where people plant trees and observe the tree’s lifespan, which includes noticing “interesting bugs,” such as schools, municipalities, and scientific institutions.

A meta-analysis by researchers at the University of Florida and the Chinese Academy of Sciences combed both peer-reviewed and non-peer-reviewed literature published in China that reported on how insect species considered invasive in the U.S. interact with seven important North American commercial tree species planted in China. Illustrated here are the host tree species and the reports of their insect pests at the family level. Left bars represent host plant species, and right color bars represent families and orders of wood-boring insects. The width of each grey link reflects the number of times the insect species was reported on the corresponding host plant in the dataset from the study. (Image originally published in Dong et al 2023, Environmental Entomology)

The researchers found 60 unique wood borer records covering four orders, 39 genera, and 44 species. Longhorned beetles (Cerambycidae) were the most reported colonizers of North American trees, far eclipsing reports of bark beetles. But, of course, the scientists could not have possibly researched the dozens of North American tree species planted in China, so they chose seven that are important in the U.S. landscape and timber industries. “Those seven are likely to trigger regulatory action if a pest on those trees shows up,” says Hulcr.

Finding so few bark beetle reports surprised Hulcr, but he thinks he understands where it comes from. “Big, fun-looking pests are reported much more commonly than little inconspicuous pests,” he says. Gaping tree holes and flashy beetles grab attention, but small beetles causing tree death make it difficult to link species to their impact. As a result, Hulcr notes that the grey literature “certainly has big biases, unquestionably.”

Hulcr also acknowledges that this meta-analysis only scratches the surface of China’s information on how its insects interact with North American tree species. For example, the team could only sample literature that had been digitized.

Chinese researchers, Hulcr says, possess extensive knowledge of American trees due to their efforts in the afforestation of fallow farmlands over the last century. “Sometimes [their approach is] misinformed because they are planting monocultures of one American species, which isn’t sustainable,” he says, “but in some cases they are establishing whole forests. Regardless, they are planting lots of American trees.”

Collaborating with overseas colleagues can also help American researchers overcome obstacles to sampling infested trees. “Trees there die, and somebody puts [them] away. That’s not something I can sample and turn into data,” Hulcr says. “We have to work with people on the ground through the [local] educational system and institutions that are there and [can record] the deaths.”

To Hulcr and his collaborators, the study represents a resourceful approach to efficiently investigating the potential threat of invasive wood borers to North American trees. It also highlights an untapped well of resources and the importance of digitizing and disseminating non-English literature.

“We are helping bring literature to daylight that would otherwise go unnoticed,” Hulcr says, “and we are turning these scattered individual reports and turning them into data that is now accessible to the mainstream global community of scientists.”

Carolyn Bernhardt, M.A., is a freelance science writer and editor based in Portland, Oregon. Email: carolynbernhardt11@gmail.com.