From the ground up
grounds crew to
help care for elmse
last summer. The
Dutch elm disease that crept across
a row of elms in front of Angell Hall
and killed the last elm there two years
ago, she said, could migrate to elms on
the grassy corner by State Street or move
onto the Diag.
University forestry crews won't know
immediately if trees have sickened; it may take
as many as two years for Dutch elm disease to cause symp-
toms, Ackley said. These symptoms include wilting of the tree's
crown, or upper canopy, and browning of its leaves.
No sick trees currently stand on campus grounds, Immonen
said. "Those get taken down right away because they serve as an
infection point and are also hazardous, with falling branches,"
But Diag horticulturist Alex Sulzer pronounced a grim future
for the mature elms on campus. "With American elms, we're
basically just prolonging their death sentence," he said. "They're
all going to go."
T wo rows of spindly saplings
stand in the grass in front of
Angell Hall, sporting chicken
wire around their trunks to prevent
squirrels from gnawing their bark. Close
inspection of their leaves reveals the trees
Immonen said she obtained the trees from
the Elm Research Institute, an organization
that has developed a strain of American elm
resistant to Dutch elm disease.
"The research institute spent years collecting seeds
and cuttings from trees all over the country, looking for
trees that were resistant," she said.
The New Hampshire-based institute calls its final result the
"Liberty Elm." According to the institute's website, Liberty Elms
are clones of six genetically-different, Dutch elm-resistant trees.
The trees are visually identical in shape and size to the classic
"We're now in the 20th year and (our) trees are out there in
great number and great height," Institute director John Hansel
said. "They're on many campuses across the nation and we're
very proud of them."
Denny Townsend, a research geneticist at the U.S. National
Arboretum in Washington, said several other strains of Ameri-
can elm are considered tolerant to the disease. He listed the
Valley Forge, New Harmony and Princeton elms as tolerant in
laboratory tests. Both the Valley Forge and New Harmony were
developed at the Arboretum.
Townsend explained that while no elm is completely immune
to the disease, "in the natural environment, we don't see symp-
toms in these trees."
A lively controversy has sprouted regarding the differ-
ent strains of resistant elm. Townsend said the Liberty Elm
Planting practices common during the early 20th century wors-
ened the devastation. The close spacing of elms along city streets,
without other trees interspersed, allowed elm bark beetles to jump
quickly from one tree to the next. Also, because elm tree roots
graft, or fuse, together when they grow to a large size, infected
trees passed the sickness to neighboring trees through entwined
Although elms seed prolifically and young elms spring up each
year, the disease prevents the trees from reaching full maturity,
"We have reduced the population of elms in nature from 200
years old to 30 years," he said. "They used to live to a grand old
age ... and now they live at most to 40 years."
Barnes said the elm bark beetle was among the first of many
introduced pests that have threatened U.S. tree populations. These
include the chestnut blight and, most recently, the emerald ash
borer, first reported in 2002 and blamed for the ongoing deaths
of ash trees.
"We haven't learned our lesson very well - the lesson of inva-
sive species," Barnes said. "It's repeated over and over again."
Dutch elm disease continues to threaten the University's
small population of remaining elms, Immonen said, and peri-
odically recurs in mature trees on campus. The University
it's hard to imagine the Diag without its 10 largest trees - all
American elms that provide shade and beauty to students
studying, sleeping or throwing Frisbees on the grass.
The University grounds crew, though, won't give up more
trees without a fight. A small but dedicated corps of University
forestry experts works to protec campus elms and other trees.
Every other year, each elm gets its own version of a flu shot -
a vaccination by "elm doctor" Immonen. Immonen runs insect
and disease control for Grounds and Waste Management's for-
estry division, and sallies out each summer with a student intern
and a long-needled, hand-held inoculation gun.
"We do trunk injections with fungicides," Immonen explained.
"That we have any elm trees standing is attributable to the fact
that we do fungicide treatment."
Immonen also uses sticky traps to monitor elm bark beetle
populations on campus. A small vial on the traps releases a
pheromone. or scent chemical. which "smells like a female
4w " .
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