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[Marc Imlay]

POINT OF VIEW

A plant pest gains a foothold


By STEVE HILTNER


Locally and throughout the country, battles are being waged that will
determine what our natural areas, city streets and even our backyards will
look like 20 or 30 years hence.

Will the Blue Ridge Parkway still turn brilliant colors in the fall? Will
there be any maples still standing to shade your house?

That depends on whether the Asian Longhorned Beetle, lethal to maples and
other tree species, can be successfully contained and eradicated in Chicago,
New York and Toronto.
Will oaks still line our streets and supply food to wildlife?

That depends on whether sudden oak death, an introduced disease that has
reportedly just spread to the East from California due to lax inspection of
nursery stock, can be quickly tracked down and kept from gaining a foothold.
That disease also threatens rhododendrons and azaleas.
Meanwhile, the emerald ash borer, another introduced insect, is killing ash
trees in Michigan and has spread thus far to Ohio.

These are some of the high-stakes battles, made necessary by weak
regulations on international and interstate trade, which typically use an
innocent-until-proven-guilty approach to restricting the movement of
potentially invasive plants and animals between nations and within the
United States. These battles, currently underfunded, will determine whether
your shade tree will eventually be replaced by a gap in your bank account
for tree removal.

Playing for lower stakes are all the backyard gardeners who burn up valuable
weekend hours contending with expansionist patches of exotic bamboo, English
ivy, Japanese stiltgrass or Chinese wisteria, whether their own or spillover
from next door.

It is the awareness of all my neighbors' lost hours, and the takeover of
natural areas by these same exotics, that has inspired me to lead the battle
against a new invader in the Triangle. Though it's one of the worst pest
plants afflicting natural areas and backyard gardens in Northern states, gar
lic mustard's entry into North Carolina has been more recent.
. . .
Like some other invasives, garlic mustard, Alliaria petiolata, was
introduced to this continent as a potherb by early settlers. Now it carpets
woodlands in the Midwest, on the East Coast and along the Appalachian Trail,
releasing toxins through its roots to inhibit the native plants it is
rapidly displacing. Wildlife, from deer to butterflies, reject garlic
mustard, increasing its competitiveness with native plants. In early summer
its 3-foot flowering stems turn brown, giving the landscape a stricken look.
I thought the Triangle had been miraculously spared this pest, until I found
it three years ago growing along a tributary of Ellerbe Creek that flows out
of downtown Durham. How it hitchhiked into Durham is unclear, but the future
is easy to guess. If left unchecked, year by year it will spread across the
city and down Ellerbe Creek to Falls Lake, eventually becoming established
throughout the Neuse River basin.

Motivated by this nightmare vision -- of further ecological degradation of
the Piedmont, of hapless gardeners and park stewards burning more hours
battling yet another exotic weed -- we have been striking while the garlic
mustards are still few in number and limited in scope. Eradicate them from
Ellerbe Creek and we just might spare all lands and people downstream,
including Raleigh.
This year, our ragtag army included two Ellerbe Creek Watershed Association
volunteers, four Duke students and a passerby who offered to wade into the
creek in her tennis shoes to help out. That doesn't sound like many, but the
fact that we cleared nearly all the garlic mustard from several miles of
creek in 21 total hours speaks to the cost advantage of stopping new
infestations before they become overwhelming.

The coincidence of our weed-pulling with Earth Day cleanups sponsored by the
city allowed us to merge weed-pulling with trash cleanup. Bottles, cans and
garlic mustard -- essentially a biological pollutant -- all went into the
same garbage bags for landfilling.

Because garlic mustard seeds remain viable in the soil, we will have to
return to the creek next year, and for several years after that, making
thorough sweeps until no garlic mustard is found. Maybe some grants will
come along to sustain these quiet struggles to save our natural heritage;
maybe state government will adequately fund a rapid reaction force to
eradicate small infestations such as this.
In the meantime, as you enjoy the shade of an oak, the beauty of maples in
fall splendor and the time you didn't spend weeding garlic mustard from your
garden, realize that nothing can be taken for granted.


Steve Hiltner now lives in garlic-mustard-infested New Jersey but still
travels monthly to Durham to do field work. The Ellerbe Creek association's
Web site is www.ellerbecreek.org


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Garlic mustard, Alliaria petiolata



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