It’s Bug Versus
Bug in the Fight
By Todd McLeish
he mixed hardwood forest on the edge of the
town of Dalton in western Massachusetts
looks healthy to the untrained eye, but the researchers
from the University of Massachusetts who visited the
site every few weeks last summer are anything but
untrained. They quickly noted the small holes made
in some trunks by foraging woodpeckers and distinguished them from the even smaller holes made by
wood-boring beetles. And staring into the canopy, they observed
that many of the trees were in the early stages of decline.
The forest, which consists primarily of white ash and red
maple, is owned by the nearby city of Pittsfield to protect its
public drinking-water supply. But now it also serves as a living
laboratory to test a variety of methods for controlling the
emerald ash borer, an iridescent green beetle native to China
that has killed hundreds of millions of ash trees in the eastern
and central United States and in Ontario and Quebec.
The invasive beetle was discovered near Detroit in 2002 and
has relentlessly spread in all directions, reaching New York in
2008, Massachusetts in 2012, and New Hampshire in 2013. It’s
only a matter of time before it reaches the forests of Vermont and
Maine. Unchecked, the beetles are expected to kill almost all of
the mature ash trees in the region in the next decade or two.
So researchers are looking for methods to control the invasive beetle and to protect future generations of ash trees. In the
Dalton forest, select trees have been injected with a systemic
pesticide to test whether adjacent trees also benefit from the
treatment, but such methods would be hard to replicate on a
landscape scale. In light of this, the forest is primarily home to
a series of biological control experiments to determine whether
the emerald ash borer’s natural enemies in Asia might succeed
at keeping the insect in check here as well.
At one of these experiment sites, research fellow Ryan
Crandall wandered the forest carrying two medicine bottles
capped with a fine mesh. Inside the bottles were coffee filters
embedded with emerald ash borer eggs, and inside the eggs
were the larvae of Oobius agrili, a tiny parasitic wasp that is one
of several insects that scientists hope will do in the US what they
do in China – control emerald ash borer populations so native
ash trees can continue to thrive.
Spathius galinae, native to Russia, is a parasitoid of emerald ash borer that has been
approved for release to help control the invasive beetle here in the US.