Upon settlement, the American Elm was the dominant tree in American river bottom ecosystems. Adapted to periodically saturated soils with low oxygen content, these trees are very well adapted to the poor soils of urban environments. Their habit of arching outwardly created gothic arches, elegantly shading the streets of our growing nation. Many towns planted 100% American Elms in their urban forests.
A fungal disease from Europe was introduced to our continent in 1928 when Veneer logs were shipped to Toledo via the St. Lawrence Seaway. Shortly after arrival, European Elm Bark Beetles began to emerge from these European logs. Spores from this vascular disease covered their bodies and were spread to the native American Elms growing nearby. Soon, the Elm trees around the shipyard started to die. If we had only known what was going on at this time, the disease could have been stopped. These beetles can fly up to 40 miles per year so by 1989, 58 million trees had been killed across the Midwest and Canada.
Once infected, there is no cure. Branches from infected trees begin to flag, or turn yellow by early summer. These trees completely die by fall. A secondary way that the disease can spread is through the roots of adjacent trees. When Elms are spaced within 50 feet of each other, root graft transmission is likely and there is no cure from this type of systemic infection.
High Value Elm trees can be protected for 3 years with a fungicide injection of “Arbotect”. We continue to treat some very sentimental or historic trees for over 30 years successfully where all other trees in the neighborhood were killed long ago.
This story of global homogenization continues to be repeated over and over withIncreased global trade with no restriction or fumigation treatment. Emerald ash Borer parallels this story in that infested wood in the form of untreated pallets or crating material was brought down the St. Lawrence Seaway, escaping into the surrounding Ash Trees and now we are in the midst of losing another highly dominant tree species. Within a few decades, all of the unprotected Ash trees in North America will be gone.
When will we learn from our mistakes?