Photo courtesy of David Cappaert, Michigan State University; Bugwood.org
As if laying waste to millions of ash trees weren’t enough, it appears that emerald ash borer has decided to move on to greener pastures.
A researcher at Wright State University in Dayton, Ohio, has determined that EAB is infesting Chionanthus virginicus—white fringetree—in Yellow Springs, Ohio. Since his initial discovery, additional infestations have been found at the Cox Arboretum in Dayton, the Ferncliff Cemetery in Springfield and in an arboretum in Cincinnati.
Don Cipollini, a Wright State biology professor and director of the school’s Environmental Sciences Ph.D. program, has been studying EAB for more than 10 years. He made the first discovery while inspecting a planting of fringetrees and came upon the characteristic “D”- shaped exit hole. He collected larvae and an adult specimen trapped in the bark; these were submitted to experts at USDA’s Animal Plant Health and Inspection Service (APHIS) as well as USDA-ARS (Agricultural Research Service) for positive identification.
“DNA tests proved to be unnecessary for identification,” Cipollini said, because the adult specimen was male, “and in particular you need males for final, positive, morphological identification.
“So the ID has been confirmed,” he continued, “but it’s been confirmed on the basis of morphological traits. DNA analysis is continuing, but now it’s to answer different questions, about whether the EAB that we find in fringetree is different in any way from the EAB that we find in ash trees; evidence of adaptation, for example.”
Photo courtesy of The Dow Gardens Archive, Dow Gardens; Bugwood.org
According to Scott Pfister, Pest Management Division Director for USDA’s APHIS, PPQ (Plant Protection and Quarantine) and Plant Health Programs, researchers at the USDA’s Systematic Entomology Laboratory at the Smithsonian Institution in Washington, D.C., have further confirmed the insect to be Agrilus planipennis. “Based on these findings,” Pfister stated, “APHIS PPQ is conducting studies to determine the full extent to which EAB is able to complete its lifecycle and utilize white fringetree as a host.”
Cipollini adds, “The most parsimonious explanation is that it’s the same old EAB that attacks ash trees, and it’s just now encountering fringetree enough, and that [the tree] is acceptable enough, and that it’s landing and ovipositing and the larvae are succeeding on it.”
Photo courtesy of Debbie Miller, USDA Forest Service; Bugwood.org
Without additional reported sightings, it’s difficult to estimate the current spread of EAB to fringetree. At present, Cipollini says, “it’s at about 20 percent” of the trees he inspected.
Chionanthus virginicus is related to EAB’s preferred host, Fraxinus species, and “in that regard, fringetree probably has more similar chemistry to ash trees, producing volatile attractants that overlap what ash tree does, and that attracts the adult [EAB] to it,” Cipollini says.
This newly identified host is native to the eastern U.S., where it grows wild from New Jersey to Florida and west to Oklahoma and Texas. It has become a popular ornamental in other parts of the country, grown for its unusual and showy, fragrant, spring-blooming flowers. It can be grown as a small flowering tree or multistemmed shrub, reaching 12 to 20 feet tall with a similar spread.