The University might be less green this spring with 200 to 250
fewer ash trees around campus. These deaths are not attributed to
pesticides or clearing of land, but rather to a small beetle, known
as the emerald ash borer.
Out of the 900 ash trees on campus, the University has already
removed 192 in efforts to prevent the spread of the beetle. Several
more trees are expected to die as spring progresses. But, 100 new
trees will be planted on campus during the next few months to
replace the old ones and to increase the amount of foliage on
campus.
The University’s ash trees are primarily located on North
Campus in the family housing area and around campus parking by
Michigan Stadium, said Facilities and Operations spokeswoman Diane
Brown.
The beetle, native to China, has triggered a near-statewide
epidemic, dramatically affecting tree populations everywhere. Its
negative effects will be worse than those recently experienced with
the European Gypsy moth or Dutch elm disease, said Marvin Pettway,
University supervisor of forestry and horticulture.
“In China and Russia it’s not a major problem
because it’s probably native and has its own population
control. Here, it is exotic and so it is out of population control
mechanisms. It’s running rampant,” Pettway said, adding
that there is no biological regulation of the beetle in the United
States.
The Michigan Department of Agriculture quarantined ash trees in
13 affected Michigan counties in the fall of 2002, after it first
isolated and identified the insect as a major pest to ash trees the
previous summer.
The quarantine, originally scheduled to expire on Aug. 5, was
extended indefinitely last Thursday, until the beetle risk has been
eliminated.
University Forestry Assistant Jane Immonen said, as of now,
there are no guidelines defining the severity of the risk or when
the risk can be defined as under control.
“We’re going to need to find some kind of natural
way to control this. We need to find some natural environment with
enemies,” Immonen said.
Pettway said there will be less of an overall impact on campus
forests than in other parts of the state where Ash trees are more
dense. Ash trees make up nearly 6 percent of trees on campus and 10
percent of Michigan forests.
“We take great effort in keeping our trees healthy.
We’ve been very diligent in caring to not have an
undiversified tree population. Because our forest is very
diversified, we won’t be as impacted as much as surrounding
community. … Five percent of campus trees have been
affected,” he said.
The beetle, about half the size of a penny, is most destructive
in September when it is growing out of its larva stage. Feeding on
sapwood beneath the tree’s bark, the larva starves the tree
of its nutrients and eventually kills branches and entire
trees.
Because leaf dropping is a natural process that also occurs in
the fall, the large dead branches of an ash tree will not be
apparent until the following spring, Pettway said.
By cutting down trees, the campus may face a heat problem as
paved surfaces absorb the sun, Immonen said.
“Urban heat island is where there is a lot of pavement and
you get a lot of heat absorption from the sun,” she said.
“Tree cover kind of blocks the sun and you don’t get as
much heating. It will take a few years for the nursing industry to
keep up with bringing in more trees. The nursing industry is 25
percent ash trees.”
The city of Ann Arbor has defined measures that will be taken to
eradicate the pest.
The steps include encouraging the community to gain information
about the borer, monitoring and marking infested trees, removing
dying trees infested with the pest, improving capabilities for wood
disposal and replacing dead trees in a timely manner.
In the past two years, the University has taken different
approaches to eliminate the pest, including the injection of
insecticide treatments into the soil surrounding a tree and
underneath its bark.
“We were still saving when I was hearing other communities
were removing dead trees. We were postponing the death of the trees
longer than other communities were,” University Facilities
and Operations spokeswoman Diane Brown said.
Pettway said the $40,000 that has been provided by University
Maintenance for tree removal is insufficient to remedy the pest
epidemic while sustaining standard tree maintenance.
“Something has got to give. (The pest) is not really ever
going to be under control. We’re handling it but at the risk
of campus trees in terms of cultural practices — fertilizing,
cabling, watering, bracing. We have to look at cost management in
regards to percent of total resources to be managed. Primary means
is saying we have to remove these trees,” Pettway said.
Dead trees are being ground and used as mulch around campus. In
the process, the wood is dried out and the insect dies.