International Researchers Mobilize Against Risky Stowaway Pests

New Zealand’s forest biosecurity program is one of the most well-developed in the world. These logs at the Port of Tauranga were fumigated prior to export to minimize the chances of accidentally spreading forest pests. Photo by Frank Koch.

Sometimes there’s more to global trade than meets the eye. While consumers and economies may benefit from expanding market opportunities and a seemingly endless array of readily available goods, harmful pests could be lurking as people and products are transported between countries. An international research network, including scientists from the U.S. Forest Service, has come together to share information about how exotic animals, diseases, and plants can move and spread—and threaten agricultural and natural resources.

The International Pest Risk Mapping Workgroup (IPRMW) consists of governmental and academic scientists from around the globe who study potential stowaway pests in order to assess the likelihood of their establishment in new locations and the impacts if and where they spread. Frank Koch, a research ecologist with the Forest Service Eastern Forest Environmental Threat Assessment Center and founding member of IPRMW, develops maps that show possible pathways for invasion when forest pests are unintentionally carried in shipments of wood products and packaging, nursery plants, and even firewood bound for family camping trips.

“Forest pests represent an interesting research problem,” says Koch. “They can dramatically alter the forested landscape, yet often remain poorly understood and difficult to characterize. A lot of my research involves trying to figure out the role of humans (and human behavior) in facilitating pest invasions, which requires a little bit of armchair psychology.”

Many people in the United States have seen firsthand the devastating impacts of forest pests. Insects such as the emerald ash borer and hemlock woolly adelgid and pathogens such as chestnut blight and Dutch elm disease have wiped out entire populations of trees in forests and urban areas. Koch’s research often focuses on high risk pests that are not yet established in the United States, but could do serious damage if they were. He is particularly concerned about the citrus longhorned beetle, an insect native to Asia whose bark-tunneling larvae could threaten several U.S. tree species, as well as leaf-eating insects like the Asian gypsy moth and the nun moth. “So far we’ve been able to avoid the establishment of these two defoliating species, which are highly attracted to the artificial lights common on large shipping vessels. But our border biosecurity isn’t foolproof,” says Koch.

Species native to the United States also can pose threats abroad. For example, the pinewood nematode, which causes pine wilt disease but causes few problems for healthy trees in the United States, became a major pest in Japan during the 20th century and was also found in China, Korea, Taiwan, and Portugal. And the Eastern gray squirrel, at one time a desired pet in Europe, has spread steadily across Europe and Asia and caused local extinction of the native European/Eurasian red squirrel through competition and introduction of a deadly virus.

The task of assessing invasion risk of so many potential pests may seem daunting, but knowledge generated by Koch and other IPRMW collaborators is supporting policy makers engaged in international trade issues. Armed with information from IPRMW efforts, they can develop science-based decisions about precautions necessary during international trading activities to prevent losses and sustain healthy crops, livestock, forests, and economies around the world.

For more information, email Frank Koch at

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