Dutch Elm Disease

During the 2005 drought-riddled summer, residents may have noticed a number of elm trees in their own and surrounding yards, which appeared perfectly healthy weeks before, suddenly become completely defoliated and dead weeks later. Diagnosis: the lack of water during the 2005 growing season enhanced the spread of Dutch Elm Disease on our elm population.

Dutch Elm Disease, which is a fungus clinically known as Ophiostoma ulmi, is believed to have made its way to the United States in the early 1920’s via elm logs from Europe. The fungus was originally spread by the Elm Bark Beetle and also by people transporting elm logs and branches. The disease was first discovered in some eastern states such as Ohio, Connecticut, Maryland, New Jersey and New York in 1930. Dutch Elm Disease reached the Pacific coast by the 1970’s.

As the disease has spread throughout North America, millions of elm trees have been infected and killed by the fungus. One of the most common elm trees in our area, the American Elm, is extremely susceptible to Dutch Elm. Although all native elms are susceptible to the fungus, elms such as the Lace Bark Elm and the Siberian Elm are highly resistant to the disease and normally don’t die once infected.

Dutch Elm Disease is most easily detected during the early summer when the leaves on upper branches start to wilt and turn brown or yellow. Other areas on the elm will look green and vibrant but will also wilt and yellow weeks later.

The Elm Bark Beetle will carry the fungus from infected trees to healthy trees as they feed on twigs and branches. The beetles lay their eggs in the bark and wood of unhealthy trees. The emerging larvae form underneath the bark and the fungus grows through the bark grooves until it reaches the tree’s water-conducting cells or xylem tissue. The disease can also be spread through root grafts. Root grafts between trees are especially prevalent in cramped areas where the elm trees are close together.

If the disease is detected early and infected branches are removed quickly along with different types of fungicide treatments, which should only be applied by a certified arborist, an elm tree may be able to resist invasion from the fungus. However, by the time Dutch Elm is discovered, the conducting tissue has already been severely incapacitated and death of the elm is imminent. Once an elm has died from Dutch Elm disease, the tree should be immediately taken down and properly disposed of to prevent the spread of the disease to surrounding elm trees.

Elms are one of the more common species of trees found in Palos Park’s landscape. They add to the diversity of our rural forest. The elm tree is an important part of our community and should be continually planted in our community to maintain a healthy species balance. When planting young elm trees, contact your local nursery to find out what newly developed species of elm are Dutch Elm resistant.