WSU sentinel plantings to guard against invasive pests, diseases at Washington ports

One of the largest shipping gateways in the Pacific Northwest, the Port of Tacoma will become home to a new WSU-developed sentinel planting, designed to catch and identify invasive pests and diseases before they spread.

TACOMA, Wash.—Aiming to catch and identify invasive pests and diseases before they impact Washington farms and forests, scientists at Washington State University will plant trees and shrubs as sentinels at the Port of Tacoma.

Funded by the U.S. Department of Agriculture Forest Service’s Office of International Programs and drawing on the involvement of community scientists, the Port of Tacoma, USDA, and the Washington State Department of Agriculture, the sentinel planting is the first of its kind at a Washington port. If successful, plantings at other port cities in the state could follow.

“If an invasive species comes through the port, we want to detect it before it becomes widespread,” said WSU professor and plant pathologist Gary Chastagner. “Sentinel plants, watched by trained scientists and volunteers, are an early warning system for potentially devastating insects and pathogens.”

As gateways for imported goods and materials, ports can allow unwitting entry to globetrotting pests and diseases.

“Invasive species can hitch a ride on anything that moves,” said co-investigator Todd Murray, director of WSU’s Puyallup Research and Extension Center and vice chair of the Washington Invasive Species Council. “Once they’re here, there are no predators or natural controls to keep populations from getting out of hand.”

Pacific Northwest invaders like the northern giant hornet, the Japanese beetle, and the emerald ash borer have made headlines in recent years. The ash borer, found in Oregon in 2022, is one of the most destructive invading pests in history, killing millions of trees in the eastern U.S. and Canada.

“Forests there are dramatically different from what they were a century ago,” Chastagner said.  “Chestnut blight, Dutch elm disease, and now emerald ash borer have wiped out stands of several iconic tree species and changed the forest composition.”

Emerald ash borer larva feeding on a tree branch.
An emerald ash borer larva works its way around a branch. This invasive beetle, responsible for devastating losses in tree species, was recently found in the Pacific Northwest. Sentinel plantings could help limit or stop the spread of such pests.

Eyes out for suspicious problems

As part of the two-year, $200,000 pilot project, WSU scientists will train community members to help monitor collections of native- and non-native sentinel plants. Besides the port, a companion sentinel garden is planned at the WSU Puyallup Research and Extension Center, seven miles south.

Joseph Hulbert, WSU co-investigator and director of the Forest Health Watch community science program, is surveying civic groups, regulators, and foresters to identify important plant species for inclusion. Options range from Douglas and noble firs and bigleaf maples to redwoods, Evergreen huckleberries, and Pacific rhododendrons.

“Input from anyone who cares about our forests and communities is valuable,” Hulbert said.

“The purpose is also to find out which pests the community is most interested in monitoring—which are the biggest threats,” said co-lead investigator Marianne Elliott, a Puyallup-based WSU plant pathologist who studies how to prevent infestations from invasive pathogens.

The sentinel survey dovetails with statewide efforts happening this spring to educate the public on invasive pests. April 2023 is Invasive Plant Pest and Disease Awareness Month, declared by the USDA to highlight the impact of invasives on plants nationwide.

Community members made the first report of the northern giant hornet near Blaine, Wash., and detected Phytophthora ramorum, the sudden oak death pathogen, at a botanical garden on Bainbridge Island.

“Educated members of the public are very effective in detecting invasive species,” Murray said

The main limit to the sentinel grove’s scope isn’t space, Chastagner said—it’s the time and expertise required to understand the health of plants on site.

“It’s critical for people to know the diseases—and their symptoms—that we already have,” he said. “The key is people asking, ‘What is this? Is this new or different?’, when something unusual appears.”

“Protecting our landscapes and resources is a shared responsibility,” Hulbert said. “We need to learn and work together to limit and reduce the impacts of invasive species on our lands. The more people engaged in this work, the more resilient we will be.”

• To learn more or get involved, visit the Sentinel Tree Planting Project website, or contact Joseph Hulbert at

•If you find signs of new, invasive pests or diseases, report them to your local WSU Extension office, or to the Washington Invasive Species Council, which offers smartphone apps to assist with sighting:


  • Gary Chastagner, Professor of Plant Pathology, 253-445-4528,
  • Joseph Hulbert, postdoctoral researcher, Forest Health Watch director,
Bags of collected plants lie on a tarp as a worker  in a protective suit moves through a wooded area.
Scientists remove plants infected with Phytophthora ramorum, the sudden oak death pathogen, discovered in Washington by community members and now a serious concern. A new sentinel planting being developed by WSU researchers aims to prevent spread of invasive pathogens and pests.