Posted 11 August 2008. PMN Crop News.
Emerald Ash Borer Arrives in Missouri
University of Missouri. cafnr.missouri.edu
Columbia, Missouri (August 1, 2008)--They're here: Emerald ash borers, which have killed tens of millions of ash trees in eight states, are now in Missouri. On July 23, USDA scientists discovered seven of the insects in traps in Wayne County in southeast Missouri.
The arrival of the emerald ash borer ( EAB) in Missouri was unwanted but not unexpected, said Hank Stelzer, University of Missouri Extension forester and member of the state's EAB task force, which includes representatives from USDA, MU Extension and the Missouri agriculture, conservation and natural resources departments.
In mid-August, Stelzer will host an online seminar ("webinar") for federal, state and MU Extension stakeholders.
"We have been preparing for an event like this for some time," said Collin Wamsley, Missouri Department of Agriculture entomologist. "Right now, we are doing what we can to determine the location of the emerald ash borer. We hope to have that information soon and begin the next steps in battling this pest."
The emerald ash borer is a small, metallic-green beetle native to Asia. As an adult, the beetle nibbles on leaves, inflicting relatively little damage, but EAB larvae burrow into ash trees to feed on the inner bark (phloem), leaving meandering tunnels that disrupt the transport of water and nutrients. Afflicted trees typically die in three to four years.
The beetles were discovered in traps at a campground at the U.S. Army Corps of Engineers' Greenville Recreation Area in Wayne County. Crews are now conducting a visual survey of trees in the area to determine the extent of the infestation, said Rob Lawrence, forest entomologist for the Missouri Department of Conservation.
Ash trees make up about 3 percent of Missouri's forests and as much as 14 percent of trees in cities and towns. "While the borer will not have a significant impact on Missouri's forest products industry," Stelzer said, "it could have a devastating impact in communities across the state. For example, the vast majority of the trees surrounding the Gateway Arch in St. Louis are green ash."
Because standing dead trees are a public safety threat, cities and towns could end up spending millions of dollars removing afflicted ash trees, he said.
The emerald ash borer was unknown in North America until 2002, when entomologists discovered it was devastating ash trees in Michigan. Since then the borer has appeared in Illinois, Indiana, Ohio, Pennsylvania, West Virginia, Virginia, Maryland and Ontario, Canada. Missouri marks the borer's westernmost appearance.
Entomologists believe borers arrived in the U.S. as stowaways in wooden shipping materials, such as crating or pallets, and have since spread by hitchhiking on firewood, ash logs and nursery stock.
Officials are urging people to obtain firewood locally and not transport firewood to or from campgrounds. The Missouri EAB task force is not yet advising landowners to change their scheduled timber management activities. For new planting, however, Stelzer said it's not a good idea to plant ash trees right now.
"Unless a miracle happens, this is going to end up a little worse than the American chestnut blight," said Steven Kirk, MU Extension integrated pest management specialist. In the early 1900s, a fungus began killing American chestnut trees, which were an important food crop and source of lumber until the blight virtually eradicated them from the U.S. by 1950.
"With the American chestnut, at least the roots are still alive and the tree can grow 8-10 feet before the disease kicks in," Kirk said. "With the borer, the tree is dead, dead, dead."
White ash and green ash trees have become popular in recent decades because they are resistant to gypsy moths, which have aggressively defoliated trees in North America for more than 100 years.
Lawrence, the MDC entomologist, notes that one lesson from this is to plant a variety of trees rather than stick to a single species. "If you do, eventually a bug will come along that only likes that tree," he said.
"There are no commercially available insecticides to combat this pest at the present time," Stelzer said. "But one promising chemical, called Tree-age, is being evaluated by research scientists in Michigan, Ohio and Indiana, and will hopefully be approved for use in other states."
In China, scientists have observed parasitic wasps attacking eggs or larval stages of the emerald ash borer. "Efforts are underway to determine if these wasps could be safe and effective controls of EAB in America," Stelzer said.
For more information about the emerald ash borer, see snr.missouri.edu.