Wright State University biologist shows the invasive Emerald Ash borer, which has killed tens of millions of ash trees across North America in the past decade, has found a new host.
After decimating tens of millions of ash trees in Canada and the United States, the invasive Emerald Ash Borer has developed a taste for a new, regionally threatened tree species known as the White Fringetree.
Research published in the Journal of Economic Entomology this week by Wright State University biologist Don Cipollini showed Agrilus Planipennis, an invasive green beetle native to Asia and eastern Russia, has made the leap from ash trees to one of their cousins.
Between August and October 2014, Cipollini studied 20 White Fringetrees (Chionanthus virginicus) in the Dayton, Ohio area near his Wright State University lab. The specimens were located in a variety of settings from the Cox Arboretum in Dayton to the village of Yellow Springs and the Ferncliff Arboretum and Cemetery in Springfield. His on-site visual and laboratory studies found external symptoms of an ash borer attack, including “adult exit holes, canopy dieback, bark splitting, and other deformities.”
According to the report:
After removing the bark from one of the trees, [Cipollini] found evidence that at least three generations of emerald ash borer larvae had used the tree, and he saw several live larvae that were actively feeding. In addition, he found a dead adult that has been confirmed as emerald ash borer.
Cipollini suspects the boring beetle has made the jump to Chionanthus virginicus largely because of it’s own success in killing so many of the trees that once supported it. Other insects dependent on ash trees to survive have been recorded making their own transitions to the fringretree on account of the similarities it shares with the embattled ash trees of North America. It’s perhaps unsurprising, then, that the parasite responsible for the ash tree’s decline should follow and prey on the new host.
This is the first time the White Fringetree has been known to host wood borers like the Emerald.
However, while it’s worrisome the borer has moved on to the fringetree, what’s striking to Cipollini is that the move happened in many regions where a stable supply of ash trees remains. The Emerald borer appears to have identified Chionanthus virginicus as a food and spawning habitat while its preferred host is still available.
“I do not think the Emerald Ash Borer has turned to white fringetree only after running out of ash trees, but that white fringetree is similar enough chemically that they will use it somewhat even if ash trees are still around,” Cipollini told Reeves Report. “We plan to start addressing these sorts of questions soon. “
Meanwhile, he has evidence borers have been utilizing White Fringetree for many years. “It may have a wider host range than we ever thought in the first place, or it is adapting to utilize new hosts,” Cipollini said in a statement. “This biological invasion is having drastic ecological and economic consequences, and you can’t always predict what’s going to happen.”
At this point, he does’t have much concern about what impact the borer could have on other horticultural shrubs such as lilac, privet, and forsythia. While these too are within the ash family, they are more distantly related to ash than the White Fringetree, “and thus more distant chemically too,” Cipollini said.
The White Fringetree is a member of the ash family found commonly in the southeastern region of the United States, though it remains threatened at the fringes of its range. It’s planted commonly as an ornamental shrub in many parts of Canada and is capable of growing up to 30 feet tall. The fragrant white flowers the tree produces each Spring make it a favourite for gardeners and arborists.
The Emerald Ash Borer was first discovered in Canada in 2002 in the Windsor area of southern Ontario, matching earlier detections across the Detroit River in Detroit, Michigan. Costs to Canada and the United States to control and eradicate the species, in addition to removing the destroyed trees, has topped $10 billion.
Much of this cost has fallen on cash-strapped municipal governments. As of April 2014, Toronto has removed more than 20,000 dead ash trees from city property alone, in addition to thousands more on private property. Toronto’s tree canopy is worth approximately $7 billion in ecosystem services, or $700 per tree: this brings the damages caused by the borer in Toronto alone to $14 million.