Lessons from Dutch elm disease as Chicago, suburbs Gear Up to Fight EAB
By Emily Johnson – 1/27/2011
Chicago, Ill. –
The history of the tree culture in Chicago is a micro-history of trees in American cities and towns.
And history is repeating itself.
I talked to James Schuster, a plant pathology specialist at the University of Illinois Extension Horticulture Office. He outlined some of the lessons that city foresters learned from Dutch elm disease as they prepare their plans for preventing emerald ash borer (EAB).
Ash trees remain one of the most common trees in Chicago. But EAB, an Asian pest first seen in the Midwest in Michigan ensures that this is changing quickly.
Various species of the Ash tree, including white ash (Fraxinus Americana) and green ash, (Fraxinus pennsylvanica) replaced the American elm in prominence after Dutch elm disease devastated the elm population in the 1950s.
Counties and towns that could afford to–like Lake Forest and Evanston, IL., tried to save their elms by removing infected trees.
But tree management is difficult because trees are not only on public property but in private yards. It is harder to convince people to spend the money to eliminate diseased trees.
The strategy towards EAB is dependent on resources.
Some towns, like Wheaton, IL, that ignored Dutch elm, learned the hard way how costly removing trees can be. They are fighting the ash borer epidemic with public funds.
To avoid a wholesale need to replace their trees, municipalities are thinning out or removing ash trees by the hundreds and replacing them with a more diverse range of trees.
Honeylocusts were planted heavily in the 1960’s to replace elm and are now a common Chicagoland tree. Other common local trees include various kinds of maples, oaks and birches, especially silver maples and pin oaks.
Schuster advocates for a greater biodiversity in tree planting.
“We replaced the Dutch elms with just a few different trees, and whether it’s white, blue, or green ash, the emerald ash borer doesn’t care,” Schuster said. Perhaps after two widespread epidemics in our recent history, we’ll learn the lesson of biodiversity he added.
The reasons for planting monoculture were obvious—it is easier to plant, and cheaper to maintain. The symmetry was also thought to be more aesthetically pleasing.
Photographs of graceful canopies of elm along avenues are a bittersweet testament to our incomplete understanding of urban arboriculture. Their beauty is sadly past. Chicago arborists hope to avoid the same mistakes with the emerald ash borer epidemic.
Emily Johnson is a Chicago freelance writer who has written for Industry, National Geographic and Penguin Putnam.