In the ongoing battle to protect Pennsylvania's state tree, the state
is increasing the amount of Asian beetles being released into forests.
The beetles prey on Woolly Adelgid, small aphid-like insects threatening
eastern hemlock trees in state forests. Brad Linder has more.
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Predatory Beetles
The state is introducing an alien insect solution to an alien insect
problem.
June 21, 2002
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More than 8-thousand Pseudoscymnus
tsugae beetles have been released in 25 sites across the state this
year to help combat the Hemlock Woolly Adelgid problem in Pennsylvania.
Rich Pais is president of Ecoscientific Solutions, an environmental
firm in Scranton.
 He
says the tiny Adelgid sucks the sap out of a hemlock tree, and in
sufficient quantity can destroy an entire hemlock forest in less than
a decade. Pais says it's not just trees that suffer from an infestation.
"There are 96 bird species and 47 mammal species in eastern North
America that depend at some point in their life cycle on the hemlock,"
says Pais. "So the loss of these hemlock trees directly affects
a wide variety of mammal and bird species."
Pais says Woolly Adelgid are native to Asia, not the United States.
So when the insects were accidentally introduced in Virginia in the
1950s, they had no predators and have been able to creep their way
up the east coast wreaking havoc on natural ecosystems.
Pesticides are one way to deal with the problem, but Pais says importing
another species of insect from Asia has also proven rather effective.
"The beetle that we're producing, Pseudoscymnus tsugae, only
eats Hemlock Woolly Adelgid," he says. "And it will only
reproduce if it gets to eat Hemlock Woolly Adelgid eggs."
That means the beetles will thrive as long as there is a food source,
and will lay dormant if the Adelgid population is brought under control.
While the Pseudoscymnus tsugae are not the only Asian predators of
Hemlock Woolly Adelgid, they are the only species that has been approved
for large-scale release in the U.S., because of this dependency on
the Adelgid. A more general predator could cause its own damage to
the ecosystem.
Each beetle raised in a laboratory and released into the wild costs
about two dollars, and offers an alternative to spraying the forests
with chemicals.
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