SPRINGFIELD -- Illinois faces a threat to its native black walnut trees in the coming years if a new invader cannot be slowed or stopped.

SPRINGFIELD -- Illinois faces a threat to its native black walnut trees in the coming years if a new invader cannot be slowed or stopped.


Tree experts are worried that Thousand Cankers Disease could kill valuable black walnut trees, a hardwood tree prized for its lumber.


Foresters are surveying Illinois walnut trees, looking for signs of the disease, which has devastated walnut trees in the western United States since the 1990s.


It recently has been found east of the Mississippi River, as close as Knoxville, Tenn.


The disease is spread when the walnut twig beetle carries a fungus from one walnut tree to another. Dead areas of branches and trunks, called cankers, lead to the tree’s demise within three years of symptoms being recognized, said Guy Sternberg, an author and arborist from Petersburg.


Sternberg is calling for a swift response from state government to stop the free movement of walnut nursery stock and wood products through Illinois.


‘Keep it out’


Pennsylvania acted once the disease was found there earlier this month.


Sternberg says Illinois must act before the disease is found.


“If it’s not here yet, let’s keep it out,” he said. “Let’s impose a quarantine, make it strict and enforce it.”


Jeff Squibb, spokesman for the Illinois Department of Agriculture, said no regulations are currently in place.


“But they are being considered,” he said by email Tuesday. “The results of the survey will help us determine what, if anything, is needed.”


“We need an external quarantine to stop this at the borders,” Sternberg said.


Minnesota recently restricted the importation of trees and lumber from infected areas.


It’s not the first time states have tried to slow the spread of a deadly invader.


States also have imposed quarantines on the movement of ash wood from areas where the emerald ash borer has been discovered.


The emerald ash borer is a tiny, metallic green beetle whose larvae girdle twigs of ash trees, eventually killing them.


Millions of ash trees have been destroyed since the insect was first discovered near Detroit, Mich., in 2002. It probably arrived in wood packing crates.


A quarter of Illinois counties already are in the emerald ash borer quarantine area.


While Sangamon County is in the “high risk” category, the borer has been confirmed in McLean and Champaign counties.


 


Native bug


Unlike the emerald ash borer, the walnut twig beetle is a native insect.


However, it was restricted to the southwestern United States and the species of walnut tree in that area -- the Arizona walnut -- was resistant to the fungus it carried.


The beetle has dramatically expanded its range in the past 20 years.


“It spread through western states where there was less resistance,” Sternberg said.


It was believed that the Great Plains would be a barrier to the disease’s movement.


“Then they found someone had transported it to Knoxville, then in Virginia about a month ago and about a week ago in Pennsylvania,” he said.


Black walnuts, common in the eastern United States, are particularly susceptible.


“All we can do is delay the spread into Illinois,” he said.


 


Chris Young can be reached at (217) 788-1528@comcast.net


 


Bur oaks also face threat


Beware of BOB.


Another potential hazard for native Illinois trees is the bur oak blight – also known as BOB.


The blight has not been officially recognized in Illinois, although it is known to occur in neighboring Iowa.


“My in-laws have a huge bur oak, even older than their house that was built in the 1840s,” said Alana McKean, manager of Starhill Forest Arboretum near Petersburg.


“It was dropping a lot of leaves in late summer and looking sickly,” she said. “The tree had lost a substantial number of leaves, so I told them to send in some samples and it turned out to be bur oak blight.”


McKean said the tree, located near Cedar Rapids, Iowa, has been treated. Some treatment options are effective against the newly discovered fungus.


It is not known yet whether the Cedar Rapids tree will need a repeat treatment.


“We are going to keep an eye on it for a few years,” she said. “We will test it next summer to see if the fungus is knocked back.”


 


-- Chris Young