Notes on Invasive
Species
There
are many advantages to living in a global economy, but there
are also costs. One of these costs is the accidental introduction
of exotic species, of which about 1 in 10 go on to establish
in their new habitats and become invasive. Such biological invasions
now occur at an unprecedented rate and scale. It is estimated
that in the United States alone, more than 4,500 foreign species
have established themselves in the past century. These biological
invasions result in severe, often irreversible impacts on agriculture,
recreation, and natural resources as well as threatening biodiversity,
habitat quality, and ecosystem function. Invasive species are
the second greatest threat to native species (after habitat destruction)
and have directly caused the decline of nearly 49% of endangered
and threatened species in North America. The financial cost of
invasive species to the United States in total economic damages
and associated control costs is estimated at about $137 billion
per year.
Like
most Midwest states, Indiana was inundated with a number of invasive
pests of regulatory concern in 2004. In addition to actual finds
of invasive species, Indiana maintains a constant vigil for exotic
species that threaten the Midwest region. Since this is an entomological
newsletter, let’s first look at the invertebrate component
of these invasions, which began right away in January 2004 with
the discovery of longhorned beetles (Chlorophorus sp.)
and tortricid moths (Cydia spp.) discovered in
pine cones from India sold in potpourri mixes for the holidays.
Although only larval (not adult) beetles were found, several
adult moths were collected. Asian ambrosia beetles (AAB)
were collected in nurseries in three southern counties in Indiana
during 2004. First detected in South Carolina in the 1970s,
this scolytid bark beetle is a pest of numerous trees, notably
(in Indiana anyway) honey locusts and orchard trees. The buprestid emerald
ash borer (EAB) was the most problematic invasive insect
in the entire Midwest region last year. EAB was detected
in two Indiana counties, LaGrange and Steuben, in 2004. This
was no surprise as Indiana borders both Michigan and Ohio, which
are also battling this pest. If EAB is uncontrolled, it
could remove North American ash trees as a species from the continent.
An estimated 40,000 ash trees in Indiana will be destroyed by
the spring 2005 in an effort to halt the pest, which has already
killed 8 million ash trees in the Detroit area. Surveys continued
for the European woodwasp (Sirex noctilio) which
was intercepted by warehouse workers in Bloomington, Indiana
in 2002. Fortunately, no positive specimens have been collected
to date and a possible crisis was averted by the warehouse workers’ actions
in reporting their find to the authorities. Total trap
catches of European gypsy moth were down 75% from 2003,
from 23,000 to about 9,000. The Indiana Department of Natural
Resources (IDNR) will treat 22 sites for gypsy moth based on
these catches in 2005, down from 39 sites in 2004. Surveys
for Old World bollworm were initiated in Indiana in 2004. Although
this insect is not currently known in the United States, over
49% of the continental U.S. is considered suitable habitat for
it. Old World bollworm is a highly polyphagous pest of
many economically significant crops and feeds on over 180 cultivated
and wild species. No specimens were collected and surveys will
continue in 2005. Another longhorned beetle (Callidiellum sp.)
from Asia was found in wooden trellises in Wisconsin last year. The
Indiana Department of Natural Resources recovered 8 trellises
from around Indiana and collected 2 larvae from the trellises. A
joint survey between the USDA APHIS PPQ and the Indiana CAPS
program for solid wood packing pests was performed at
55 sites in Indiana in 2004, targeting 16 invasive bark and wood-boring
beetles. o targeted pests were collected during the survey,
but the serendipitous discovery of banded elm bark beetles (BEBB)
in Marion County, Indiana during the survey made the efforts
worthwhile. BEBB, a pest of elm trees, was first found
in 2002 in Utah and Colorado but is now quite widespread. Trapping
for BEBB and other invasive bark beetles will continue in 2005. Five
new counties in southern Indiana were added and placed under
quarantine for pine shoot beetle (PSB). Currently, 60
of 92 Indiana counties are under quarantine for PSB, which arrived
in the U.S. in 1992. In December of 2004, brown fir longhorned
beetle (Callidiellum villosulum) was found in the
real-wood (complete with bark) trunk of an artificial Christmas
tree from China by a consumer in Michigan. Prior to the
discovery, the distributor sent shipments of these artificial
trees to Illinois and Michigan. So far none have surfaced in
Indiana but there is some concern because of the proximity of
the shipments.
Of
course, all invasive species aren’t insects; there are
many pathogens of concern. Indiana participates in the
USDA’s national
survey for the fungal disease karnal bunt, providing information
to support the karnal bunt–free status of grain exports
from the United States. The USDA regulates wheat infected with
karnal bunt, restricts the wheat’s movement to retain export
markets that consider it a pest of quarantine significance, and
keeps the fungus from spreading. Fortunately, all samples taken
in 2004 from Indiana were negative. A pest of national concern
(it even appears on the USDA’s Agricultural Bioterrorism
Act of 2002 Select Agents and Toxins list) is the bacterial pathogen Ralstonia
solanacearum. It causes common wilt in geraniums and
infects numerous solanaceous plants (e.g., tomatoes, and peppers)
and is a major concern to the potato industry. The ralstonia
survey resulted in no detection of this pathogen in Indiana,
but, because of the seriousness of this pest, future surveys
are planned. In the spring of 2004, potentially infected ornamental
plants were shipped throughout much of the U.S. containing that
fungal pathogen Phytophera ramorum which causes Sudden
Oak Death. The plants
came from a few nurseries on the West Coast (California and Oregon)
that inadvertently shipped containerized rhododendron, camellia
and other plants that might have been infected with P. ramorum.
IDNR Nursery Inspectors recovered 70 camellias in Indiana that
originated from the West Coast shipments. Twenty Indiana nurseries
were then surveyed using national protocols (Elisa tests and
PCR) and 600 nurseries were surveyed visually but so far no positive
finds from this pathogen were found in Indiana.
Of course, Indiana
is also susceptible to invasion by plants. Giant hogweed was
found near Warsaw, Indiana (Steuben County) this year. This
invasive plant is a high priority for detection and control
due both to its threat to human health. Giant hogweed causes a skin reaction known as photo-dermatitis
which results in large painful blisters with eruptions on humans.
The Indiana Department of Natural Resources also conducted a
survey for kudzu, the infamous strangling vine of the
South that has unfortunately made its way into Yankee territory.
So far in Indiana 55 kudzu sites have been found in 24 counties,
for a total of 55 acres. Kudzu
grows well under a wide range of conditions and in most soil
types. Besides threatening landscapes, kudzu acts as an alternate
host for soybean rust. Brazilian elodea was
found during an IDNR plant survey of another invasive plant,
the Eurasian water milfoil. This aquatic invasive
plant was found in Bloomington's Griffy Lake and was treated
by the Bloomington Water Company. Elodea,
which forms in dense mats, threatens biological diversity by
crowding out native plants and animals. Yellow floating heart,
a popular garden ornamental that is an aggressive grower with
the capability to establish in natural areas, was found on 3
private properties in Indiana last year. Fish and wildlife habitat,
recreation, and water quality is negatively impacted when the
dense mats of yellow floating heart outcompete native and beneficial
plant species. The concern is that it will get into major rivers
such as Wabash River and Sugar Creek River.
Last, but not least,
there are vertebrate invasives. The European wall lizard became
the first invasive lizard found in Indiana and was detected at
the Falls of the Ohio State Park. The lizard has the potential
to reach high populations densities and to displace native species
of lizards including the 5-lined skink. Finally, the Indiana
Department of Natural Resources issued a quarantine banning the
sale of the Giant African land snail. Giant African land
snails can carry the rat lung worm, which can cause individuals
who eat raw or undercooked snails to develop meningitis and to
suffer from permanent neurological damage. Approximately 200
Giant African Land Snails were collected and incinerated from
owners in Muncie and Wabash, Indiana.
Although Indiana
is seemingly landlocked, we certainly do not lack invasive species.
Fighting them, although extremely costly and time-consuming,
is well worth the effort to preserve our natural resources.
~ Christopher M
F. Pierce ~