USA's trees under relentless attack from bugs, blight
Pastor Dale Morgan
USA's trees under relentless attack from bugs, blight*
Updated 10/24/2006 11:13 AM ET
Egg masses of the hemlock woolly adelgid look like cottony tufts on twig
stems. The insects suck the sap of the tree, halting new growth and
killing the tree within a few seasons.
TREES UNDER ATTACK
Species threatened from Hawaii to the Atlantic coast:
• Oak: Sudden oak death, from spores that spread in wind-driven
rainstorms, is killing millions of trees along the north coast of
California and in south-western Oregon.
• Ash: The emerald ash borer, whose larvae burrow lethal tunnels beneath
the bark, has killed more than 20 million trees since its discovery near
Detroit in 2002. It spread to Ohio and Indiana, and outbreaks have been
found in Illinois and Maryland.
• Eastern hemlock: The hemlock woolly adelgid, an Asian bug that
gradually spread through the East and Southeast, has jumped to northern
Michigan.
• Wiliwili: An African wasp is destroying groves of wiliwili, a
flowering tree native to Hawaii. Scientists believe the erythrina gall
wasp, which attacks the tree's leaves, arrived on Maui last year.
By Patrick O'Driscoll, USA TODAY
DENVER — Some of the USA's most treasured tree species, from ash and
aspen to white pine and Hawaii's native wiliwili, are under attack by
insects and diseases in a growing assault coast to coast.
Some of the killers are foreign pests brought here in cargo or by
travelers. Others are homegrown insects at epidemic levels because of
drought and unusual warmth. This year has been the warmest on record.
The Agriculture Department's Animal and Plant Health Inspection Service
finished adopting new rules this summer barring cargo from abroad unless
crates and pallets are treated with chemicals or heat to kill any bugs
in the wood.
"We're at one of those points in time where it's all happening at once,"
says Wayne Shepperd of the U.S. Forest Service.
The mountain pine beetle, a native, has ravaged millions of acres of
Western forests. Trees were weakened by drought or subjected to worse
infestations because warmer temperatures allowed the bugs to multiply
faster. The emerald ash borer from Asia is killing species that have no
natural defenses.
Ash borers can spread in diseased trees cut up for firewood. The
Agriculture Department airs radio ads in eight states and has billboards
that warn: "Pack marshmallows, not firewood."
BATTLING THE ASH BORER: Asian invader feeds on foliage
California's Big Sur region and Sonoma and Humboldt counties have "tons
of new mortality this year" from sudden oak death, another disease, says
Katie Palmieri of the California Oak Mortality Task Force. "Entire
hillsides are just gone."
A nursery shipment is blamed for spreading the hemlock woolly adelgid
into Great Smoky Mountains National Park in Tennessee and North
Carolina. The park hopes to save older hemlocks by using insecticides
and beetles that eat the aphid-like bugs.
Scientists don't yet know what is killing aspens across much of the
West. "This die-back just occurs, boom, and we're not seeing new
sprouting" of trees, Shepperd says. He says drought is a possible cause,
but "we see (aspen) dying in wet areas, too, so I'm not convinced it's
drought alone."
A study this year in BioScience said exotic bugs and diseases "pose the
most serious current threat to the forests of eastern North America."
Posted 10/23/2006 11:05 PM ET