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
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
1920ís 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 1970ís.
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 donít 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 treeís 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
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
Elms are one of the more common species of trees found in Palos Parkís
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.