Last week, a college biology professor in Ohio announced he had found evidence that the emerald ash borer (EAB), an invasive insect decimating the continent’s ash trees, is also attacking white fringetrees (Chionanthus virginicus).
In August he found the telltale D-shaped exit holes on a fringetree near his home. When he investigated further by peeling back the bark, he found feeding galleries and live borers. He had the borers positively identified morphologically as well as with DNA tests conducted by the USDA’s Animal and Plant Health Inspection Service (APHIS). He also found evidence of EAB activity on fringetrees in three other locations in Ohio.
The recent discovery marks the first time EAB has been found completing its life cycle on anything other than ash in the United States.
The finding adds an alarming new element to the EAB story:
- Researchers have been wondering whether the host range for EAB could be wider than just ash. That theory had seemed unlikely up to now but is proven with the fringetree discovery. There has already been a lot of research investigating other possible hosts, and with the new discovery, there will likely to be more.
- Is the insect adapting? This is a scary thought!
- Will EAB kill fringetrees as it does ash, or just cause damage? So far the invasive insect appears to only be damaging—not killing—fringetrees.
- Has EAB moved to fringetrees because EAB populations are locally so high? If the buffet is crowded at the “prime rib station,” it seems logical that “meatloaf station” may get some visits.
- What will happen when ash tree populations dwindle? Will the EAB population die back, or just move to a secondary host (the meatloaf, as the prime rib is gone) and/or develop a completely new palate?
The Ohio professor’s find was not all by luck; he had reason to focus on the white fringetree. Laboratory studies have shown that the adult EAB will feed on the foliage of other tree species in the same family as ash—the olive family, or Oleaceae. Members include ash (Fraxinus), fringe tree (Chionanthus), lilac (Syringa), forsythia, privet (Ligustrum) and swamp privet (Forestiera). Literature from Asia, the homeland of the EAB, indicates other secondary EAB hosts.
The Chicago Botanic Garden has 42 fringetrees; all have been inspected and show no signs of EAB activity. Even a fringetree that is 25 feet from an ash tree that was heavily infested with EAB shows no signs. If you have a fringetree, you should inspect it for signs of EAB. These include dieback starting at the upper limbs of the tree, new growth on the lower trunk, and small, D-shaped holes where the larvae have exited through the bark. Emerald ash borer larvae can kill a mature ash tree in two to three years by destroying the tree’s vascular system.
As the world has become less fragmented by ease of transportation, more exotic, high-consequence plant pests and pathogens like EAB have entered—and will continue to enter—the country. Other exotic plant pests and pathogens we are watching for at the Garden include the following: viburnum leaf beetle, Asian gypsy moth, brown marmorated stink bug, Asian longhorned beetle, thousand cankers disease, plum pox virus, chrysanthemum white rust, sudden oak death, and so on; most are already in the country. Vigilance and education are the key to managing and slowing the spread of these foreign invaders.
The Garden is a member of the Sentinel Plant Network, a group that unites botanic gardens in monitoring and providing education on exotic plant pests and pathogens, and works in partnership with the National Plant Diagnostic Network (NPDN).
If you are a plant and bug person like me, please consider becoming a NPDN First Detector and help be on the lookout for these exotic plant pests and pathogens. The NPDN offers an online training course to become a First Detector at firstdetector.org. It’s free, and upon completion, you even get a printable certificate!
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