N.H. is home to an international alarm system made of trees

The so-called sentinel gardens spanned three continents and four countries, including Sweden, China, Italy, and the United States. New Hampshire is home to one of two sentinel gardens in the US. The other is located at the Waterman Farm on the Ohio State University Campus in Columbus, Ohio.

Researchers involved in the project hoped to make new discoveries about which insects and pathogens harm different plants.

Isabel Munck, a plant pathologist for the US Forest Service who works in Durham, N.H., was among them.

“One of the biggest threats, if not the biggest threat to our forest in this part of the world are invasives, like pathogens and insects,” said Munck.

If the researchers noticed a tree struggling, they could investigate which pathogens or pests were likely to blame.

Foreign invasives can hitch a ride into the US in wood products, packing materials, or on live plants imported by nurseries, for example. But native plants haven’t developed any resistance to those insects or diseases, which means they can be especially damaging or even lethal.

Munck said she was especially interested in learning more about fungi, which make up most forest pathogens.

“The point of this project is to try to detect them before they spread,” Munck said. She likened the trees planted abroad to a canary in a coal mine, capable of alerting people to a problem before it becomes lethal.

She worked on one of the sentinel gardens, located at the Urban Forestry Center in Portsmouth, N.H., where plants from China and Europe were grown.

Gardeners in Italy, Sweden, and China reciprocated by growing plants from New Hampshire in those three countries to see how they would respond to pathogens located in those countries.

Researchers in China found several new pathogens that impact red maple that had never been reported before, according to Munck.

These observations could be used to inform policy decisions about monitoring and preventing harmful pathogens from entering the country to protect forests.

“We’re not going to stop international commerce and movement of goods and services and people. It’s an attempt to not be surprised by things that have surprised us in the past,” said Pierluigi Bonello, a plant pathology professor at The Ohio State University. Bonello also directed the sentinel garden research project.

“This is just step zero, not even step one, just to see what’s out there,” he said. “Once you know there is a potential threat, theoretically then, you can alert the border inspection facilities in the United States, for example, to be on the lookout for that specific organism.”

When invasive species go undetected, they can create big problems.

Beech leaf disease is one of the top concerns Munck sees in the region today, caused by nematodes, or microscopic worms, that are believed to come from the Pacific Rim. First detected in the US in 2012, it prevents beech trees from developing shoots so the trees stop making new leaves. It has been found in 13 states so far, including New Hampshire, Massachusetts, Connecticut, Rhode Island, and Maine.

Scientists are concerned about the rate of spread, and that the invasive can kill trees just a few years after symptoms first show up.

Munck is also studying trees at the Arnold Arboretum of Harvard University to see what kinds of fungi are already present here. The 281-acre arboretum has over 16,000 trees, including species from all over the world. Some of the same species that grow in the arboretum were planted in the sentinel gardens around the world, so Munck can compare the fungi present in Boston to those in Jiangsu Province in China, for example.

“We’re trying to exclude the things that are always present from the ones that are causing disease,” Munck said.

Amanda Gokee can be reached at amanda.gokee@globe.com. Follow her @amanda_gokee.