By Roger Witherspoon
Copyright 2004 The Journal News (Westerchester County, NY)
The Journal News
November 30, 2004 Tuesday
RogeBreed that resists beetle-borne fungus planted in Putnam
The Journal News
There are no elms on Elm Road in Briarcliff Manor.
"There used to be elms on Elm Road," Brooke Beebe, director of the Native Plant
Center in Valhalla, said of the street where she lives. "But they're gone. There's not
one elm tree left on Elm Road, and that's a shame. Elms are native trees, and they
were once all over the place."
Beebe's street isn't unique. American elms, which once dominated suburban
neighborhoods across the nation and New England forests, have all but disappeared
from the landscape.
"The elm tree was the tree of choice to be planted by small towns all across the
country," said Lydia Dallis, an Ardsley gardener and president of the board of the
Cornell Cooperative Extension Service for Westchester County. "They have a
beautiful shape and will hang over and provide a wonderful canopy for residential
streets."
But then came Dutch elm disease, a parasitic fungus carried by the European elm
bark beetle.
During the past 50 years, the disease and failed government prevention measures
contributed to the eradication of most of the nation's stately elm trees. But after
years of research and false starts, the elm is making a comeback. Thousands of
clones of a disease-resistant strain of American elm are being grown in special
nurseries and replanted across the country by homeowners and local governments.
Putnam County is spreading around the new trees, including two 30-foot American
liberty elms planted this month in front of the county's historic courthouse to replace
two weeping elms killed by the fungus.
"There were elm trees in front of the Putnam County Court House in the 1920s, but
Dutch elm disease ravaged those trees and practically every other elm in America,"
said George Whipple, a Kent resident who donated the trees to the county. "These
new trees will be the biggest elms in Putnam County because all the rest are dead."
Neither Westchester nor Rockland county has added the elm to its tree-planting
program. But Ardsley has planted a row of the cloned elms in Ashford Park, and
White Plains is annually planting about 25 of the elms.
"We're putting them all over," said Joseph "Bud" Nicoletti, White Plains' public works
commissioner. "Whenever a tree has to be removed, we make a note of where it was
and bring in an elm."
Planting disease-resistant trees is the latest and most promising effort to prevent the
American elm from disappearing. But it took years of research into tree physiology
and genetics before researchers hit on a scheme that worked.
"The problem was we were trying to beat Mother Nature and couldn't," said John
Hansel, director of the Elm Research Institute in Keene, N.H. At first, Hansel said, it
wasn't clear how the trees were being killed and it was believed that the beetle itself
was the culprit.
"The little beetle has no knowledge of what he is doing," Hansel said. "He just
happens to be a carrier with the fungus spore on his whiskers. Nothing affects the
beetle and when he takes a bite out of the little growing wood and wipes his
whiskers, the process begins."
In 1955, the Department of Agriculture adopted a policy of tree isolation in which
elms found within about a mile of an infected tree would be cut down and burned.
"The government thought the trees were spreading the infection and said, 'Let's burn
them down faster than they can get infected,' " Hansel said.
Under the isolation program, more than 100 million elms were cut down across the
country - yet the disease continued to spread. It was then realized that the disease
was spread by the beetles and efforts were taken to control the disease. Researchers
tried unsuccessfully to develop a kind of "Franken-wasp" that could bore through elm
bark and kill beetles and beetle larvae. But the creationist effort failed.
The government then tried controlling the beetle population with traps, and millions
were captured and destroyed. "But Mother Nature just made more," Hansel said.
"We finally realized we would have to defeat that parasite when he walks in the door
and forget the idea of going to his house and trying to cut down the baby beetles."
Researchers at Cornell and Syracuse universities began studying what was actually
killing some elms and why others survived - lone elm trees that seemed to thrive in
the midst of the dying trees. It was then that they discovered the fungus.
"It is a cancer of the tree world that was choking off the water supply by clogging the
trees' vessels," Hansel said. "The tree then died of thirst."
The surviving trees managed to fight back by having extremely slow metabolisms.
Their slow-moving sap prevented the fungus from spreading far, and gave the trees
time to counterattack by walling off the infected site with a layer of bark. The
fungus, starved of sap, dried up and died.
Researchers found that clones of these naturally resistant elms had a better than 90
percent chance of surviving new infestations of the disease. So for the past decade,
the Elm Research Institute and private nurseries have grown clones of those elms
and restocked the nation's streets and parks.
In time, more elms may again be found on the nation's Elm Streets.
Reach Roger Witherspoon at rwithers@thejournalnews.com or 914-696-8566.
LOAD-DATE: December 2, 2004