Invasive and Non-native Terrestrial Invertebrates
in the Lower Coos Watershed


  • Although no invasive terrestrial invertebrate populations are currently established in the project area, experts have identified the forests of western Oregon as a high risk ecosystem for invasion; continued monitoring is needed.

  • Invasive terrestrial invertebrates are potentially costly economic and ecological threats to the project area even beyond potential threats to locally harvested tree species.

Emerald ash borer Photo: emeraldashborer.info

Emerald ash borer Photo: emeraldashborer.info

Asian long-horned beetle deposits eggs in firewood. Photo: Environmental News

Asian long-horned beetle deposits eggs in firewood.
Photo: Environmental News

Table 1. Summary of potential invasive insect threats to the lower Coos watershed.

Table 1. Summary of potential invasive insect threats to the lower Coos watershed.

What’s happening?

While many benign non-native terrestrial
invertebrates (insects) are established in the
project area, none are currently considered
invasive; that is, no non-native insects are
known to be responsible for local ecological
or economic damage, or threaten human
health. However, it’s important to note that
the risk of future invasive insect introductions
is very real. In part because, like any community,
the Coos Bay area is exposed to invasive
species introduction through any number of
“vectors.” These include the transport of firewood,
living plants, and freight packed wooden
packaging material (see sidebar below).

Due to the abundance of tree cover and the
economic importance of the local timber
industry, this section focuses on non-native
wood boring insects that represent the largest
potential economic and ecological threats
to the project area. These species include
the emerald ash borer (Argrilus planipennis),
Asian long-horned beetle (Anoplophora
), gypsy moth (Lymantria dispar
), and balsam woolly adelgid (Adelges
)(Table 1). None of these species are
currently established in the project area.
However, should they become established
locally, they would pose significant threats.

Emerald Ash Borer
Argrilus planipennis

The emerald ash borer, native to eastern
Russia, northern China, Japan, and Korea
(McCullough and Usborne 2011; OSU 2011),
was first detected in Detroit, Michigan in
2002. Since detection, the emerald ash borer
has spread gradually and is now found in
25 states and two Canadian provinces. The
westerly extreme of its range has reached

Although the emerald ash borer
is not currently found in Oregon, experts
believe that the future introduction of this
species could result in potentially tremendous
economic and ecological costs (OSU 2011).
Experts believe that the emerald ash borer
was inadvertently introduced to North America
when infested wood was used in crates
or stabilizing cargo in ships (McCullough and
Usborne 2011; Carlson and Verschoor 2006).
Adult emerald ash borers deposits eggs in the
crevices of true ash trees (i.e., Fraxinus spp.).

After emergence, insect larvae damage or kill
their host trees by consuming the tree’s cambium
(i.e., layer of live inner bark), interrupting
the flow of nutrients throughout the tree
(Carlson and Verschoor 2006; OSU 2011).

Emerald ash borer damage has been extensive
in the eastern United States. Kovacs and
colleagues (2010) estimate that emerald ash
borer infestations have caused approximately
$10.7 billion in damage, resulting on the
removal or replacement of approximately
17 million ash trees by 2019 in the Midwest,
Mid-Atlantic, and Northeast states alone. In
Oregon, the introduction of the emerald ash
borer could jeopardize native populations of Oregon ash (Fraxinus latifolia), the only
species of true ash that occurs in the project
area (Pojar and MacKinnon 1994; OSU 2011).

How Invasive Insects Are Spread

Invasive insects can spread through a variety
of mechanisms, including the long-distance
transport of wooden goods, plants,
or trees. For example, the interstate transportation of firewood and other wooden
goods (e.g., patio furniture, pallets) can
spread invasive wood-boring insects.
Similarly, the use of wooden packaging
materials (e.g., crates, wood shavings,
wooden supports) may encourage the
spread of these same species. In addition
to the transport of wooden goods, the
spread of insects may be facilitated by the
movement of ornamental plant species
and nursery stock.

Source: USDA 2006, 2015; OSU 2011

Williams (pers. comm. 2015) explains that
although the emerald ash borer does not
target commercially harvested species, its
introduction represents potentially substantial
economic costs to the timber industry if
introduction is accompanied by additional
regulation (e.g., quarantine, mandatory inspection
of mobile equipment such as trucks).
He adds that the use of pesticides to control
emerald ash borer infestations could also
potentially affect water quality. In addition
to these possible costs, the introduction of
the emerald ash borer to Oregon could also
decrease habitat complexity by threating the
viability of Oregon ash populations in ecologically
important areas (e.g., riparian zones)
(OSU 2011).

Asian Long-horned Beetle
Anoplophora glabripennis

The Asian long-horned beetle, native to China
and Korea (Haack et al. 2010), was likely first
introduced to Brooklyn, New York in 1996. It
has since spread to several eastern states, including
New Jersey, Massachusetts, Ohio, and
Illinois as well as Ontario, Canada. Although
its spread has been contained to the eastern
United States, experts suggest that an Asian
long-horned beetle invasion of western Oregon
forests would result in extensive ecological
and economic damage (OSU 2011).

The Asian long-horned beetle was inadvertently
introduced to the eastern United
States in wood packing materials (Haack et al.
2010; OSU 2011). It damages hardwood tree
species, including, but not limited to, maples
(Acer spp.), birch (Betula spp.), ash (Fraxinus
), poplars (Populus spp.), willows (Sa lix spp.), and elm (Ulmus spp.)(Haack et al.
2010). Similar to other invasive wood boring
species, Asian long-horned beetle larvae
damage healthy trees by consuming their vascular
tissues, resulting in structural weakness
and tree death (OSU 2011; Haack et al. 2010).
Since its introduction to North America, Asian
long-horned beetle damage has been extensive
and costly in the eastern United States. If
allowed to proliferate, the estimated magnitude
of nationwide damage is significant. According
to Nowak et al. (2001), from 1997 to
2008, Asian long-horned beetle infestations
caused $373 million of damage to forests in
Illinois, Massachusetts, New Jersey, and New
York alone. They estimate that Asian longhorned
beetle infestations could cause a loss
of 1.2 billion trees nationwide (valued at $669
billion) if the insects are allowed to continue

In Oregon, the potential ecological effects of
Asian long-horned beetles are also significant.
Although this species would not affect Oregon’s
dominant conifer species (e.g., Douglas
fir, Port Orford cedar, hemlock), the insect is
likely to infest native hardwood species (e.g.,
Oregon ash, big leaf maple, alder)(OSU 2011).
These hardwood species provide important
ecosystem services, including nutrient cycling,
erosion control, and habitat complexity. They
add that Asian long-horned beetle infestations
could also result in significant economic
costs where extensive beetle damage may necessitate the removal of large trees in urban
settings (OSU 2011). Similar to the emerald
ash borer, the Asian long-horned beetle may
also result in significant costs to the timber
industry if infestation within or in proximity to
the project area results in additional regulatory
measures (Williams pers. comm. 2015).

Figure 2. A delta trap, used to detect European and Asian gypsymoths, to facilitate early detection of these species. Source:ODA 2015.

Figure 2. A delta trap, used to detect European and Asian gypsy
moths, to facilitate early detection of these species. Source:
ODA 2015.

Asian Gypsy Moth
Lymantria dispar asiatica

The Asian gypsy moth is similar to European
gypsy moths in many ways, but Asian gypsy
moths are known to feed on a wider range of
host species and cover much larger distances
in flight (USDA 2015).

Asian gypsy moths were first introduced to
North America near the Port of Vancouver,
British Columbia in 1991, likely from ships infested
with egg masses arriving from eastern
Russia. Since its arrival, the Asian gypsy moth
has spread to parts of the Pacific Northwest,
including Washington and Oregon. A secondary
inadvertent introduction (again from
infested cargo ships) occurred on the east
coast of North Carolina shortly thereafter
(1993). Since then, Asian gypsy moths have
been detected and largely eradicated on at
least 20 separate occasions in locations across
the United States. Though still intermittently
detected in Oregon, local Asian gypsy moth
eradication efforts have been successful thus
far due to early detection and rapid response
(USDA n.d., USDA 2015).

Figure 3. Asian gypsy moth egg masses on the inside of a vehicle wheel. Photo: Australian Department of Agriculture 2015

Figure 3. Asian gypsy moth egg masses on the inside of a vehicle wheel. Photo: Australian Department of Agriculture 2015

Beginning in 2009, the United States Department
of Agriculture has taken preventative
measures against the Asian gypsy moth by requiring foreign trading partners to participate
in rigorous inspections of ships at the time of
departure from foreign ports and again during
entry at domestic ports. Although these preventative measures have been effective, Asian
gypsy moths continue to be detected periodically
in the United States, spread by a variety
of means (e.g., Figure 3)(USDA 2015).

European Gypsy Moth
Lymantria dispar Linnaeus

The European gypsy moth was first introduced
in the late 1860s, when the species
was brought to Massachusetts from Europe
for the purposes of silk production (USDA
2003b). Quickly realizing the alarming potential
for damage, the Massachusetts
State Board of Agriculture began attempts
to eradicate European gypsy moths using
methods that ranged from manual removal of
egg masses to systematic forest burning and
application of primitive pesticides (Figure 1)
(USDA 2003b).

The United States Department of Agriculture
(2008) explains that gypsy moths cause a
substantial amount of damage by defoliating,
weakening, and ultimately killing host trees,
including broad-leafed hardwood species (i.e.,
oak, apple, alder, willow, birch, madrone, cottonwood)
as well as coniferous species that are abundant and harvested commercially
within the project area (i.e., Douglas fir, pine,
and western hemlock) . They add that gypsy
moth infestations reduce the forests’ ability
to defend against disease, fire, and erosion,
deteriorating the quality of habitat for other
forms of plant and animal life.

Despite early control efforts, the European
gypsy moth continued to spread and established
populations throughout New England
by the 1920s (Sadof 2009). Attempts to eradicate
European gypsy moths began again in
the 1940s following the discovery of the use
dichloro-diphenyl-tirchloroethane (DDT) as an
extremely effective pesticide. But the application
of DDT for pest control was limited in the
1960s and banned in the 1970s due to public
concern about the severe environmental
affects associated with DDT use (Sadof 2009).
In the past 20 years, efforts to control European
gypsy moths via the aerial application of
alternative pesticides have once again been
reestablished (Sadof 2009; USDA 2003a).
European gypsy moth infestations remain a
serious forest management issue throughout
New England, the Mid-Atlantic, and the Midwest
(ODA 2015).

Although isolated populations of European
gypsy moths have occurred in Oregon since
the 1970s (including seven moths found in
Grants Pass in 2015) there are currently no
established populations in the state. This is
in part due to Oregon’s early detection rapid
response protocol, which include a large-scale
trapping program throughout the state (Figure
2) (ODA 2015).

Figure 1. Two workers attempting eradicate European gypsy moth by burning the forest with kerosene (c. 1890). Photo: USDA 2003b

Figure 1. Two workers attempting eradicate European gypsy
moth by burning the forest with kerosene (c. 1890). Photo:
USDA 2003b

Balsam Woolly Adelgid
Adelges piceae

Common throughout fir forests in central
Europe (Arthur and Hain 1984), the balsam
wooly adelgid first appeared on the US west
coast in 1929, most likely as a result of the
transportation of infected fir saplings to be
used as nursery stock (USDA 2006). Populations
appear to be established throughout the
range of “true firs” (Abies spp.) in Oregon and
Washington. While not yet detected in the
project area, this insect does affect local tree
species, including grand fir (Abies grandis)
(USFS n.d.).

Balsam woolly adelgids affect true fir species
by injecting a hormone into the host tree that
disrupts normal growth and inhibits cone production.
Balsam woolly adelgid populations in
the Willamette Valley have limited the reproductive
success of grand fir (Abies grandis),
and may ultimately cause the eventual disappearance
of this species from Willamette
Valley ecosystems if current trends continue.
The ability to control balsam woolly adelgid
infestations by applying areal pesticides is
limited due to the species’ ability to excrete a
proactive waxy coating. Although alternative
methods (e.g., treatment of individual trees)
have proven effective, these methods require
additional resources and are generally limited
to accessible areas supporting high-value
trees (USDA 2006).

Other Invasive Terrestrial Invertebrates:
Exotic Mollusks

According to Casper (2008), experts have
identified nearly 50 invasive mollusk species
in the Pacific Northwest. Some of these
species have caused substantial damage to
agricultural crops in western Oregon, including
for example, the gray field slug (Deroceras
), a species native to Europe
(Gavin et al. 2012). Although it’s apparent
that non-native slugs and snails are present
and causing damage in Oregon, experts are
unable to determine the exact number of
invasive terrestrial mollusk species statewide
because little is known about the presence of
these species and the extent of their actual or
potential to cause economic and/or ecological
damage within the project area (Casper


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) in natural stands and
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beetle: a worldwide perspective.
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McCullough, D. and R. Usborne. 2011. Emerald
Ash Borer: Frequently Asked Questions.
Accessed 6 July 2015: http://www.emeraldashborer.

Nowak, D. J., Pasek, J. E., Sequeira, R. A.,
Crane, D. E., and Mastro, V. C. 2001. Potential
effect of Anoplophora glabripennis (Coleoptera:
on urban trees in the
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September 2016: https://www.oregon.gov/

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University]. Accessed 7 July 2015: http://

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(USDA). 2003a. Gypsy Moth in North America.
Accessed 7 July 2015: http://www.fs.fed.us/

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E. Leopold Trouvelot, Perpetrator of our
Problem. Accessed 7 July 2015: http://www.

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July 2, 2015.