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Bromus tectorum
cheatgrass brome
This invasive grass is troublesome to farmers and many ecosystems. It usually
thrives in disturbed areas preventing natives from returning to the area.
Disturbance such as overgrazing, cultivation, and frequent fires encourage
invasion. Once established the natives cannot compete and the whole
ecosystem is altered.
B. tectorum is a winter annual. The seedlings are bright green and have hairy
leaves. Stems are erect and slender and may also be slightly hairy. The stem
tips, where the seeds are located, droop slightly. The grass has an overall fine,
soft appearance and typically grows 50-60 cm tall. As it dries out it begins to
turn purplish in colour. B. tectorum is a straw-like colour when completely dry,
which is when it is most flammable.
General impacts
As B. tectorum is such a dry plant, it increases the frequency of fires in an area.
This causes declines in natives that are accustomed to less frequent fires while
B. tectorum flourishes. The more frequent fires cause a loss of topsoil and
nutrients, which alters the make up of the soil and therefore the ecosystem. On
the other hand, B. tectorum may stabilize the soil from wind and water erosion
(Carpenter et. al, 1999). In Russia the impacts of B. tectorum are less serious,
even in regions with similar precipitation to the Great Basin of the United States.
While it will rapidly and completely dominate disturbed sites in Russia, these will
often revert to more diverse, stable communities within three to five years of the
invasion. It has been suggested that this is due to the more diverse natural
communities present in these affected regions of Russia, and the greater
Geographical range
proportion of summer rainfall that benefits perennials rather than winter annuals
Native range: B. tectorum is native to southern
such as B. tectorum. North American B. tectorum invasions cost wheat farmers
Europe and southwestern Asia.
in the western United States and Canada US$350-375 million in control and
Known introduced range: It has invaded most of
Europe, southern Russia, western and central Asia, loss yields each year. Although used by some farmers as feed, it can cause
serious damage to livestock's mouth, intestines, nostrils, and eyes. In North
Japan, South Africa, Australia, New Zealand,
Iceland, Greenland, Canada and the United States. America it competes with native shrubs and perennial grasses and totally alters
the ecosystem.
Arundo donax
bamboo reed
Giant reed is a perennial grass which has been widely introduced into primarily
riparian zones and wetlands in subtropical and temperate areas of the world. Once
established, it forms dense, homogenous stands at the expense of native plant
species, altering the habitat of the local wildlife. It is also both a fire and flood hazard.
Large statured clump-forming grass, 3-10 meters tall with many stems from a
shallow, horizontal rhizome. Stem or culm hollow with bamboo-like nodes, 1-4 cm
diam., typically unbranched the first year and forming branchlets from nodes in
subsequent years or when damaged. Leaves clasping and long (to ca. 70 cm),
alternately arranged in a single plane, the ligule fringed with longish hairs. May form
plume-like terminal inflorescence, but often non-flowering in higher latitudes
Occurs in:
agricultural areas, coastland, desert, disturbed areas, natural forests, planted forests,
range/grasslands, riparian zones, scrub/shrublands, urban areas
General impacts
Displaces native riparian vegetation and provides poor habitat for terrestrial insects
and wildlife. Traps sediments and narrows flood channel, leading to erosion and
overbank flooding. Promotes wildfire and debris blocks streamflow and damages
bridges.May reduce water availablility through high evapotranspiration.
Geographical range
Native range: Considered native to Indian sub-continent, now occurs worldwide in tropical to warm-temperate regions, inluding
tropical islands. It is present in the Federated States of Micronesia (Pohnpei), Guam (rare per Stone, 1970), Republic of Palau
(Koror), Fiji, Hawai'i, Nauru, New Caledonia, Norfolk Island and Samoa as well as Christmas Island in the Indian Ocean. An
ornamental variety, Arundo donax var. versicolor (Mill.) Stokes is widely cultivated. It has white-striped leaves and is reported to be
under cultivation in Fiji and Palau. It has been widely planted throughout the warmer areas of the U.S. as an ornamental. It is
especially popular in the Southwest where it is used along ditches for erosion control (Perdue 1958).
Sirococcus clavigignenti-juglandacearum
butternut canker
Sirococcus clavigignenti-juglandacearum, is the cause of a lethal stem disease, butternut
canker. It causes multiple cankers on the main stem, branches, and twigs of butternut, Juglans
cinerea. Cankers commonly occur at the base of trees and on exposed buttress roots and can
survive and sporulate on dead trees for at least 13 years or more. The fungus may be
threatening the viability of butternut as a species.
Host Range: Recent research studies using artificial inoculations have revealed that the
pathogen can attack other highly valuable species of the family Juglandaceae; such as black
walnut, Japanese walnut, Persian walnut, and heartnut as well as various hybrids of these
species. This wide host range of the pathogen has attracted international concern. Both
seedlings (Feberspiel and Nair, 1982) and 10 to 20 year old field planted trees of all species
mentioned proved to be susceptible (Orchard et al. 1982, Gabka 1986). In addition, black
walnuts growing in a mixed stand of severely diseased butternuts have been found infected
naturally. However, heartnut, Japanese walnut and hybrids between then and butternut exhibited
greater resistance to the pathogen, developing smaller cankers, than the highly valuable black
walnut and Persian walnut. (Nair, V.M.G. 1999)
Diagnostic Systems include elliptical to fusiform cankers formed on the main stem and branches. Young cankers originate at leaf
scars lenticells bark wounds and buds, often with an inky black center and whitish margin. Peeling the bark away reveals the brown
to black elliptical areas of killed cambium. Older branch and stem cankers are perennial, found in bark fissures or covered by
shredded bark, and boardered by successive callus layers. Cankers commonly occur at the base of trees and on exposed buttress
roots. Branch cankers usually occur first in the lower crown and stem cankers develop later from spores washing down from branch
cankers. The fungus can survive and sporulate on dead trees for at least 13 years (Nair. V.M.G, 1999). Authors of a study report that
cankers develop first on branches in the lower crown. This is followed by branch mortality and sporulation by the fungus. Trunk
cankers develop1-3 yr after initial branch mortality. The authors report that trees with tops killed by coalescing basal cankers did not
resprout at the root collar (Tisserat and Kuntz, 1984; Nair, V.M.G, 1999).
Occurs in:
host, natural forests, planted forests
Ophiostoma ulmi
dutch elm disease
Occurs in:
natural forests, planted forests, urban areas
Geographical range
Native range: The origin of the fungus O. ulmi, the causal
agent of Dutch elm disease, remains unknown but it is
probably native to Asia.
Known introduced range: O. ulmi was introduced in Europe
around 1910 and from here was introduced into America,
where it arrived around 1930. The disease is prevalent in
Canada and has been controlled in New Zealand.
Dutch Elm disease is a wilt disease caused by a pathogenic fungus disseminated by specialized bark beetles (Brasier, 2000). There
have been two destructive pandemics of the disease in Europe and North America during the last century, caused by the successive
introduction of two fungal pathogens: Ophiostoma ulmi and Ophiostoma novo-ulmi , the latter much more aggressive. The vector is
represented by bark beetles, various different species of scolyts living on elm. These beetles breed under the bark of dying elm trees.
The young adults fly from the DED infected pupal chambers to feed on twig crotchtes of healthy elm trees. As a consequence spores
of the fungus carried on the bodies of these beetles are deposited in healthy plant tissue. O. ulmis.l. can also spread via root grafts.
According to Partridge (1997), O. ulmi s.l. is a rather complex fungus. It has four spore types: conidia produced on mycelium, conidia
borne on a mycelial stalk (synnema), yeast like spores that are variable in size, and ascospores, which are produced in a black
fruiting body (perithecium) which ooze through the long neck of the perithecium, and accumulate at the tip in sticky mass.
Management information
Preventative measures: According to Stack et al. (1996), Dutch elm disease cannot be eliminated once it begins. A year-round
community sanitation program is the key to slowing the spread of the disease. The most available control is removing infected trees
and promptly destroying the wood. If infected wood is to be used as firewood, it should first be debarked. Trenching to disrupt root
grafts is also recommended to protect healthy elm trees near diseased ones. In urban situations, insecticide spraying of high value
trees has been effective in keeping bark beetles from attacking susceptible trees. In ornamental plantings, suggested control
measures include planting trees further apart to prevent root grafts or choosing mixed tree species. The use of resistant selections for
new plantations is strongly recommended.
Occurs in:
host, natural forests, planted forests
Geographical range
Native range: Asia (EPPO, 2004).
Known introduced range: Europe and North America (EPPO, 2004).
C. parasitica is a fungus that attacks primarily Castanea spp. but also has been known to cause damage to various Quercus spp.
along with other species of hardwood trees. American chestnut, C. dentata, was a dominant overstorey species in United States
forests, but now they have been completely replaced within the ecosystem. C. dentata still exists in the forests but only within the
understorey as sprout shoots from the root system of chestnuts killed by the blight years ago. A virus that attacks this fungus appears
to be the best hope for the future of Castanea spp., and current research is focused primarily on this virus and variants of it for
biological control. Chestnut blight only infects the above-ground parts of trees, causing cankers that enlarge, girdle and kill branches
and trunks.
General impacts
C. parasitica has had a negative cascading effect upon native forest composition and diversity throughout most of the United States
since its introduction. Davelos and Jarosz (2004) state that, "American chestnut, C. dentata, was a dominant overstorey species in
hardwood forests of the eastern United States of America prior to the introduction of blight (Day and Monk, 1974; Karban, 1978;
Russell, 1987). In Southern Appalachian forests, the loss of mature chestnuts may have substantially reduced the forest's carrying
capacity for certain wildlife species (Diamond et al., 2000). After the spread of C. parasitica, oak (Quercus spp.), red maple (Acer
rubrum) and hickory (Carya spp.) became the dominant overstorey tree species (Keever, 1953; Stephenson, et al., 1991). Today,
chestnuts continue to be an important understorey species because of sprouts produced by extant tree root systems (Keever, 1953;
Russell, 1987; Stephenson et al., 1991). However, infected sprout clusters exhibit reductions in survival and size, particularly when in
competition with other hardwoods (Griffin et al., 1991; Parker et al., 1993). Vandermast et al. (2002) state that, "Allelopathic qualities
of chestnut leaves could have affected large areas of eastern forests. Chestnut foliage was dense, the leaf litter abundant and the
leaves slow to decay ( Zon, 1904). Other studies indicate rain throughfall, dripping off live foliage, can contain concentrations of
phytotoxic chemicals sufficient to inhibit germination of co-occurring species ( Al; Lodhi and Nilsen). With the abundance of
competitive tree and shrub species in the southern Appalachians, it is possible allelopathy had an influence on maintaining chestnut's
dominance in the region."
Aulacaspis yasumatsui
Asian cycad scale
The armoured scale insect, Aulacaspis yasumatsui, commonly
known as the cycad aulacaspis scale (CAS) or the Asian cycad
scale is highly damaging to cycads, which include horticulturally
important and endangered plant species. The cycad scale is an
unusually difficult scale insect to control, forming dense populations
and spreading rapidly, with few natural enemies in most localities
where it has been introduced. The scale has the potential to spread
to new areas via plant movement in the horticulture trade.
All adult female armoured scale insects have a waxy outer covering for the protection of themselves and their eggs (the scale)
(Weissling et al. 1999). The scale of mature females of A. yasumatsui are: "white, 1.2-1.6 mm long and highly variable in form. They
tend to have a pyriform shape with the exuviae at one end, but are often irregularly circular, conforming with leaf veins, adjacent
scales and other objects. The ventral scale is extremely thin to incomplete. The scale of the juvenile male is similar to those of other
species of Diaspididae, being 0.5-0.6mm long, white and tricarinate, with exuviae at the cephalic end. Scales of males are nearly
always more numerous than those of females" (Howard et al. 1999). Adult males are orange-brown, and are similar in appearance to
tiny flying midges, with one pair of wings and well-developed legs and antennae (Heu et al. 2003). Adult females are also orange in
colour (Weissling et al. 1999).
Habitat description
CAS is found on plants from the gymnosperm order Cycadales, which consists of three families - Cycadaceae (Cycas a genus that
contains its preferred host species), Stangeriaceae (Stangeria) and Zamiaceae (8 genera).
Geographical range
Native range: Southeast Asia (Howard et al. 1999; Muniappan, 2005). According to Dr. Chandrashekara and Dr. A. Viraktamath of the
Department of Entomology at the University of Agricultural Sciences in Bangalore, India, CAS has so far not been recorded in India.
Please see Update on CAS native range.
Known introduced range: USA (Florida, Hawai‘i, Georgia, Texas, Alabama, California, Louisiana, South Carolina), Cayman Islands,
Puerto Rico and Vieques Islands, US Virgin Islands, Singapore, Hong Kong, Guam. Intercepted at the border in France. Intercepted
at the border in New Zealand and eradicated.
Anoplolepis gracilipes
crazy ant
This species has been nominated as among 100 of the "World's Worst" invaders
Workers of Anoplolepis gracilipes respond
rapidly to disturbance of the litter layer
Occurs in:
agricultural areas, coastland, disturbed areas, natural forests, planted forests,
range/grasslands, riparian zones, scrub/shrublands, urban areas, water courses
A. gracilipes, or the yellow crazy ant, is one of the largest invasive ants, (invasive ants are typically small to medium-sized and range
from 1-2mm to more than 5mm). This species, also known as the long-legged ant, is notable for its remarkably long legs and
antennae. A. gracilipes workers are monomorphic, displaying no physical differentiation. It has a yellow-brownish body colour, and is
weakly sclerotized. Workers have a long slender gracile body, with the gaster is usually darker than the head and thorax. It may
subdue or kill invertebrate prey or small vertebrates by spraying formic acid.
Anoplolepis gracilipes commonly known as the yellow crazy ant is associated with human-modified environments, such agricultural
areas or urban zones. On some tropical islands, including the Seychelles and Christmas Island, it has reached high densities,
devastating native invertebrate and vertebrate populations, especially previously-threatened birds. In at least one case its removal of
a keystone species has resulted in a change in forest composition and a decrease in nutrient cycling. It affects native fauna by
competing for food resources, altering the habitat or predation. By lowering biodiversity, it indirectly threatens tourism sectors. Its
relationship with various honeydew-producing insects exuberates scale insect populations, affecting native flora and causing
significant damage to plants and economic losses in agricultural systems.
Geographical range
Native range: The long-legged ant remains poorly studied and even its native range is not certain. It may have originated from Africa
or Asia (Holway et al. 2002). The centre of diversity for the genus is Africa and A. gracilipes is the only species distributed beyond that
Vulpes vulpes
Red Fox
Native to Europe, Asia, North Africa, and boreal regions of North
America, European red foxes have been introduced into Australia
and temperate regions of North America. They are now the most
widely distributed carnivore in the world and have negative
impacts on many native species, including smaller canids and
ground nesting birds in North America, and many small and
medium-sized rodent and marsupial species in Australia.
Occurs in:
agricultural areas, disturbed areas, natural forests, planted
forests, range/grasslands, riparian zones, tundra, urban areas
Three color morphs are generally recognized: red, silver or black, and cross. A pale-yellowish color morph is common on the Arabian
peninsula, and within native subspecies in North America. In general, throat and abdomen are white, lower legs and ears are black,
and a bushy tail is tipped in white. This species exhibits a wide geographic and subspecies variation in size, as body length can
range from 45 to 90 cm, tail length from 30 to 55 cm, and body mass from 3 to 14 kg.
General impacts
In Austrialia, red foxes have eliminated remnant populations of some native rodent and marsupial species on the mainland, and
evidence suggests they are the primary cause in the decline and extinction of many other small and medium-sized rodent and
marsupial species. In North America, introduced red foxes have negative impacts on many ground-nesting birds, such as ducks and
grouse. In California, introduced red foxes have to be controlled on an annual basis to protect the nesting grounds of several
endangered species of birds. Introduced red foxes also negatively impact smaller native canids, such as the endangered San
Joaquin kit foxes, and subspecies of native red foxes. Evidence suggests introduced red foxes might have already completely
replaced several native subspecies of red foxes across Canada. Introduced red foxes are also a threat to livestock, as they prey on
poultry, lambs, and kids. Finally, their high densities pose a health threat to humans and pets through transmission of diseases,
especially rabies, but also distemper, parvo virus, and mange.
Geographical range
Native range: Europe, North Africa, most of Asia (excluding extreme Southeast Asia and southern India), and boreal regions of North
Red foxes are now the most widely distributed carnivore in the world.