University of Vermont Extension
Department of Plant and Soil Science
Dr. Leonard Perry, Extension
University of Vermont
Japanese beetle, gypsy
moth, and European
corn borer are some of our more commonly known plant pests that have
abroad. Viburnum leaf beetle, Asian
longhorned beetle, emerald ash borer, hemlock wooly adelgid, and the
moth are some of our more recent introduced plant pests.
Dan Gilrein, entomologist for Cornell
on Long Island, provides some
facts about these insects and their damage.
Most of our introduced pests are the
result of human activity, either purposeful or not. If
these seemingly harmless insects are not
introduced for a particular purpose, only to escape, they more often
on wood and products in transit from other countries. Wood
boring insects, hiding in wood packing and
crates on ships, are of special recent concern.
The gypsy moth is an example of a
purposeful introduction, brought to Medford, Massachusetts
in 1869 by a French
naturalist to try and establish a silkworm industry. Some
insects escaped, and within ten years it
was obvious this pest was a problem.
The Japanese beetle was first found in
this country (New Jersey) in 1916, and
since spread throughout most of the eastern U.S.
and Ontario. The European corn borer was first found near Boston in 1917, perhaps entering the country the
prior on broom corn shipments from Europe. This pest attacks hundreds of plants,
including ornamental plants, boring into and killing stems. The linden tree, cut flowers, and dahlias are
some it attacks.
More recently in 1947 the
beetle appeared in Ontario from Europe, with breeding populations near
in 1978, and only reaching northeastern states this past decade. It defoliates and kills several viburnum
species, including some of our native ones important to natural
wildlife. Other species are less
susceptible, and are the ones to plant in landscapes if this pest is
nearby. A good listing of these species
is provided by Cornell
The Asian longhorned beetle
accidentally arrived in cargo from Asia
1996. It is closely monitored around New York City and Chicago
where it appeared, with quarantines and monitoring of plant shipments
well. It could be a serious pest if it
spreads, as it destroys hardwood trees.
Just around New York,
control efforts have cost over $280 million, with over 8,000 trees
since 1997 and almost 700,000 treated with insecticide.
The emerald ash borer is another
recent pest being closely monitored in landscapes and the nursery trade. This pest, too, accidentally arrived in cargo
First seen in Detroit
in 2002, it has since spread to surrounding states. This
is a deceptively attractive insect, as
it kills ash trees—a valuable tree in urban landscapes and rural
forests. Since 2002 an estimated 20 million
been destroyed in the affected states.
If left uncontrolled, losses are estimated at $20-60 billion.
The hemlock wooly adelgid, once
again, arrived in cargo from Asia. First seen on the west coast in the 1920’s,
it appeared on the east coast of the U.S.
in 1951. Likely it was spread in
infected landscape plants or wood.
Attacking mainly eastern species of hemlock, it has become a
rapidly spreading pest on the east coast where it has no natural
enemies. In its native Japan,
it is kept in check by a
native Japanese species of ladybug. This
pest can defoliate and kill a mature tree within four years, sometimes
less. It is destroying forest ecosystems
by killing off native hemlocks that provide a niche and many benefits
moth is only recently coming
to prominence, luckily, and is still somewhat localized.
First brought over from Europe, and found in Nova Scotia over 70 years ago, it has been in
last 10 to 15 years. Early detection
often was missed, as this insect is similar to and confused with a
others. Confirmation of its
establishment in that area was finally made in 2003. Natural
enemies don’t seem to be controlling
it, as it defoliates large areas around Boston
feeding on many trees and shrubs. The
winter moth caterpillars can cause serious damage to apples and
particular, entering unopened buds.
Destroyed buds of course result in no blooms and so no fruit.
More on these and other invasive
pests can be found through searches online, from state agriculture and
extension agencies, or at websites such as of the Massachusetts
Pests Outreach Project (massnrc.org/pests).
Visit these sites and study the photos, so you can identify
if you see them. If you think you find
one, check with one of these state agencies or your Extension Service
If you visit an area known to have such
invasive pests, resist the temptation to bring back trees and shrubs
accidentally the pest with them. This is
particularly true for plants you might dig from landscapes or get from
Susceptible plants often are quarantined from shipment within the
infested areas, so help support such prevention.
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