The future of North America’s ash trees may lie in some seeds that came from China.
The Morton Arboretum and collaborators are attempting to protect North American ash species and ensure they survive, utilizing seeds of Chinese ash species that the Arboretum’s Kris Bachtell collected recently in China. An estimated 25 million ash trees in North America have died from Emerald ash borer (EAB), and the beetle shows no sign of letting up.
After the Arboretum grows the Chinese species from the collected seeds, experts will evaluate the trees’ resistance to EAB. Ultimately, the Arboretum hopes to develop a hybrid of the Chinese and North American ash with resistance strong enough to survive an onslaught of the beetles.
“There is very good evidence there is resistance to the Emerald Ash borer in China’s ashes,” said Bachtell, arboretum director of collections and facilities. “If you want to test a species for its insect and disease resistance, it’s best to test a tree that’s not a hybrid. That’s why we collect wild seeds, to get the species’ pure form. We have few, if any, of the ash species that we collected, already on our grounds.”
Dr. Fredric Miller, arboretum research sssociate, and Kunso Kim, arboretum assistant director of collections, are already working on securing a grant for a study to evaluate the susceptibility of different types of ash to the Emerald ash borer. Though this study evaluates ash currently part of the Arboretum’s collections, future studies will include trees grown from seeds that Bachtell collected.
Bachtell traveled to a remote area southwest of Xi’an in Shaanxi Province, making 50 collections (several thousand seeds total) including five ash species: Pax’s ash, Manchurian ash, Chinese ash, Chinese flowering ash, and island ash, which is a rare species not found in the United States. He also collected seeds from hardy linden and maple species.
Joining Bachtell’s expedition were Christopher Carley from the U.S. National Arboretum, Tony Aiello from the Morris Arboretum of the University of Pennsylvania and Kang Wang, host from the Beijing Botanic Garden.
The collected seeds literally had to clear customs, and Bachtell says federal authorities have been conducting tests including X-rays to make sure that no seeds contain diseases or pests.
EAB has invaded the Illinois landscape, which is comprised of 131 million ash trees statewide, and is ravaging ash in Virginia, Maryland, Pennsylvania, West Virginia, Ohio, Wisconsin, and Missouri–hitting Michigan especially hard.
The United States Department of Agriculture (USDA) will keep many of the collected seeds in their Crop Germplasm System, a seed bank available to researchers around the world.
“I may not see the hybrid in my generation. Introducing trees is a multi-generational thing,” says Bachtell. “Trees are a long term investment. It’s a deliberate, but slow process.”
The Morton Arboretum gratefully acknowledges F.A. Bartlett Tree Expert Company for its support of the China expedition.