The two enormous, stately elm trees that
towered in front of Hill Auditorium until June had lived through so
much.

One hundred years old and more than two feet thick, they had
seen the University burgeon into a major research institute. They
stood by calmly while Ann Arbor’s young soldiers enlisted for
the first, then the second, world war.

They witnessed the first Ford automobiles on Ann Arbor roads and
weathered the droughts of the Great Depression. Their leaves blew
in the wind during the protests of Vietnam.

And for years, with the help of the University’s grounds
crew, they escaped the epidemic of Dutch elm disease that, since
1930, has killed 80 percent of Michigan’s American elm
trees.

But last year, stressed by construction at the auditorium that
weakened their root systems, the trees finally succumbed to the
disease. Both were cut down this summer to prevent the fungal
sickness from spreading to other trees.

“The death certificate says ‘Dutch elm
disease,’ but I know it was the construction … that
strained the trees to the point where they could no longer fight
anything off,” said Jane Immonen, a forestry technician for
University Grounds and Waste Management.

The two lost elms typify the fight that American elms —
and the people who love their tall, vase-shaped profile —
have waged against Dutch elm disease for decades. Although
it’s too late to save Hill Auditorium’s two trees, many
preservation and restoration efforts are paying off. At the
University, elms just might be about to begin a comeback.

A spreading threat

Once considered the foremost American
shade trees for their graceful shape, large size and rapid growth,
elms used to stand in long avenues along city streets and in front
of public buildings like Hill Auditorium. The University alone had
thousands of elms on its grounds, including the Nichols Arboretum
and the Matthaei Botanical Gardens, said SNRE Prof. Burt
Barnes.

Then Dutch elm disease, introduced to the United States from
Europe in a shipment of infected wood during the 1930s, swept in.
Transmitted by unassuming little critters less than three
millimeters long called elm bark beetles, the disease has destroyed
more than half the nation’s elm trees, the U.S. Department of
Agriculture reports.

Planting practices common during the early 20th century worsened
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
root systems.

Although elms seed prolifically and young elms spring up each
year, the disease prevents the trees from reaching full maturity,
Barnes explained.

“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 invasive 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 periodically
recurs in mature trees on campus. The University currently has 153
mature elms on campus.

This year has been particularly difficult for campus elms, she
said, due to an unusually cool, rainy summer. Fungal diseases like
Dutch elm disease thrive in damp conditions and are more likely to
overcome preventive measures protecting the trees.

Also, each elm death sends a host of homeless bark beetles
scrambling for a new, nearby home.

“If they lose their food source, they’ll move on to
the next tree,” said LSA senior Valerie Ackley, who worked
with the University grounds crew to help care for elms 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.