By Erich Wagner, Published:
June 6
In the battle against an invasive
tree-killing insect native to eastern Asia, state and federal agriculture
officials have decided to use a strategy that lets nature do most of the work.
The emerald ash borer is a species of beetle
that feeds on — and eventually kills — ash trees, which are prominently used in
landscaping as well as stormwater and erosion control.
After years of failed attempts to eradicate
or at least lessen the effect of the pests by destroying infected trees,
officials with the U.S. Department of Agriculture and the Maryland Department
of Agriculture in Cheltenham are trying to cut off the problem where it starts:
with insect eggs. To do so, they have enlisted the help of another east-Asian
insect: “stingless wasps,” which are smaller than fruit flies and lay their own
eggs as parasites in ash borer eggs, eventually killing the host.
Although the tiny wasps are not a native
species, officials said they are confident they will not become invasive.
Officials deployed the first set of wasp eggs
onto infected trees May 30. The emerald ash borer beetles are particularly
aggressive compared with native wood-boring insects, laying 70 to 100 eggs
each, eating through the interior of a tree as larvae and then feasting on its
leaves as adults, they said.
Ash borers are widespread despite earlier
eradication efforts, which involved the destruction of 27 square miles of trees
in Prince George’s County, where the region was first infested in 2003 via a
tree nursery shipment from Michigan.
Since 2003, there have been reports of
infestations in Charles, Howard, Anne Arundel, Washington and Garrett counties.
Officials said the program costs about
$300,000 each year. Prior eradication efforts had cost as much as
$1 million a year.
Charles Pickett, an agricultural inspector at
MDA, said that not only do officials anticipate the eggs being more effective
in stopping ash borers, but they hope they will be more capable of surviving
and producing an enduring population to fight the invasive insect down to a
manageable level.
“Each wasp can produce 62 eggs,” Pickett
said. “We just want to get it to an equilibrium to control the borers so
they’re not killing everything. We have native redheaded and clear-winged ash
borers, which have always been here, but they only affect trees, they don’t
kill them.”
Jian Duan, a research entomologist at the
USDA and lead scientist in the effort to stop the emerald ash borer, said the
wasps were one of several species tested before release for their potential
effectiveness against the ash borer, as well as whether they would cause any
adverse effects of their own.
MDA’s Cheltenham facility grows ash borer
eggs to send to a lab in Michigan, which uses them to cultivate the wasps for
use in Michigan and Maryland.
“[This species of wasp] and the emerald ash
borer evolved together for many years,” Duan said. “It will be very hard for
the wasps to switch to another egg.”
Dick Bean, program manager for plant
protection and weed management at MDA, said the wasp effort is one of the last
options available for saving the ash tree in Maryland. Given the region’s
abundance of waterways and Chesapeake Bay tributaries, more conventional pest
control means such as crop dustings of pesticides were out of the question.
“There’s just nothing on the market that we
can use, especially [in Prince George’s County] because of environmental
reparation efforts,” Bean said. “Biological control is one of the last hopes we
have. But there’s no silver bullet yet.”
Bean said the first batch of eggs should at
least make an impact on the ash borer population. Officials will keep track of
the effectiveness of the wasps, as well as the dispersal system used thanks to
a postdoctoral study conducted in conjunction with the effort by the University
of Maryland.
Original Article Here
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