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Results
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The overall outcome of this study is encouraging based on the following facts:
-- the cross verification error was small (23.1%)
-- the accuracy for the model test set
was high (83.3%)
-- the
chosen neural network model correctly classified 11 out of 15
species already declared as noxious that were first reported during the
1951-2000 period.
The 29 exotics predicted as potential noxious weeds in
Idaho and/or Montana follow
below.
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Alhagi maurorum
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The native range of camelthorn is from India eastward to Asia Minor and the southern states of the former Soviet Union. Camelthorn is considered to be a weed in its much of its native range. It has already been declared noxious by seven western states. An Australian quarantine weed, also invasive in South Africa. This thorny leguminous shrub reproduces mostly from its vigorous rhizomes. It is well adapted to dry barren conditions and becomes dominant in habitats where the roots can tap into shallow groundwater.
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Anthriscus sylvestris
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Cow parsely or wild chervil is known to be weedy in Europe, the northeastern U.S., and eastern Canada. Australia prohibits its introduction and it is considered to be a problem plant in Africa. It has recently begun to spread in the northwestern U.S. and western Canada. Toney et al. (1998) classified it as invasive of the Pacific Northwest. It is most successful along rights-of-way and in wet to dry grasslands and pastures, but also exhibits shade tolerance. Typically a biennial it can also have perennial growth from taproot sprouts. U.S. FDA lists as a poisonous plant.
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Butomus umbellatus
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Flowering rush is an invader of
wetlands and lakeshores. It forms monotypic stands from
rhizomes. Many wetland ecologists consider this to be a
problem species, but it has been declared noxious only
in New Hampshire. Previously ranked as invasive by Toney
et al. (1998) for the Pacific Northwest. The IUCN
Invasive Species Group has included flowering
rush in its list of the world's 300 worst invasive
species.
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Centaurea dealbata
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Reported North American distribution of Persian cornflower is limited
to Washington and Montana. The North American
occurrences may be all garden escapees, but it is
adapted to dry soils. We could not find any history of
this plant as a weed, except that it had been introduced
to Czechoslovakia and it produces an undesirably large
number of seedlings in garden plantings. It is an Asian
native from the Caucasus Mountains.
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Crepis tectorum
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Rooftop or narrow-leaved hawksbeard is considered to be a weed in Asia
(Mongolia to Japan), throughout Europe, and is now
spreading in the north-central plains of North America
where it first was noted in the early 80s. It has since
been declared noxious in Alberta, Manitoba, and
Minnesota.
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Crupina vulgaris
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Common crupina was first noted
in North America in Idaho in 1969. It is well known in
the Pacific Northwest because it was placed on the
Federal Noxious Weed List in the 1980s. Most western
states have placed it on their noxious weed lists. The
large sized seeds may slow the long distance geographic
spread rate.
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Eragrostis tef
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Tef is a grass grown as a
cereal grain crop in Africa. It is weedy and can
tolerate a wide range of conditions. The single
occurrence record (1991 Canyon County, Idaho) for the
Northwest has no site information.
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Glaucium corniculatum
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Red horn poppy is a recognized
weed in Europe, Australia, South America, and throughout
North America. It has only been designated as noxious in
North America by Oklahoma. This annual has only been
reported in Stillwater County, Montana (1964 &
1993). However, Toney et al (1998) ranked it as invasive
for the Pacific Northwest region.
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Gypsophila acutifolia
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Little is known about sharpleaf babys breath. There is only one Northwest record, from
1983 in Musselshell County, Montana, with no site
information. The only other reports in North America are
for Alberta and Wisconsin. This perennial is adapted to
dry, sandy and stony slopes, but has no known weedy
behavior.
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Gypsophila elegans
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Showy babys breath is an annual (sometimes biennial) that
is found on disturbed sites in twenty-six states and provinces. It has no known
history of being a significant problem plant. The single Northwest record,
Minidoka County, Idaho, 1995, has no site information.
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Hemerocalli fulva
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Orange or tawny daylily is the
daylily widely used in ornamental plantings. It is a
widely distributed wetland weed in the eastern through
central U.S, and Canada. Numerous eastern and midwestern
ecologists have classified orange day lily as invasive
but there are no regulatory restrictions on this popular
ornamental.
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Hieracium floribundum
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Yellow-devil hawkweed is
closely related to meadow hawkweed (Hieracium pratense).
Montana, Washington, and Quebec have included
yellow-devil hawkweed in their noxious lists. Holm et
al. (1991) in the Geographic Atlas of World Weeds was
one of the first to note this species as a problem
plant.
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Hieracium piloselloides
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Kingdevil hawkweed is closely
related to meadow hawkweed (Hieracium pratense). Montana
and Quebec have listed this taxon as noxious. This
species has not been studied in any detail.
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Hieracium pratense
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Meadow hawkweed is widespread
in the northern Rocky Mountains. Idaho and Montana have
already declared it noxious, as well as Washington and
Quebec. It is also known to be invasive in the eastern
U.S. and Canada, Japan, and Australia.
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Lepyrodiclis holosteoides
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Lepyrodiclis is a annual weed
of croplands (grain & pea) and roadsides. Toney et
al. (1998) ranked it as invasive for the Pacific
Northwest. It has been declared noxious by Oregon and
Washington and is considered to be a problem plant in
Japan and China.
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Linaria bipartita
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Clovenlip toadflax has only one
record from Latah County (Moscow) ID, in 2000, otherwise
it has only been documented as established in
California. It has no documented history of invasive
behavior except in California and Japan.
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Lychnis x arkwrightii
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Arkwrights catchfly is a
hybrid between Lychnis chalcedonica and Lychnis x
haageana. It is promoted by horticultural flower trade.
It was reported in northeast Montana in the early
1980s, as a pasture weed. There are no other reports
for North America. Lychnis chalcedonica (Malteescross)
is a rather common weed found in most northern US states
and Canada.
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Lythrum virgatum
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Wandlike loosestrife is very
similar to purple loosestrife and seven states co-list
it with purple loosestrife as noxious.
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Matthiola longipetala
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Night scented stock was found
as a single plant in a Boise garden in 2000. It is a
weedy annual mustard. It has been reported in seven
other North American states and provinces. Australia
prohibits its import.
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Myriophyllum spicatum
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Eurasian watermilfoil, a
submerged aquatic, appears to be one of the most rapidly
spreading exotic weeds on North America. Eleven states
and provinces have declared Eurasian watermilfoil
noxious as of 2002. Idaho added it in 2001 and Montana
is proposing its addition in 2003. The IUCN Invasive
Species Group has included Myriophyllum
spicatum in its list of the world's 300 worst
invasive species.
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Origanum vulgare
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Oregano has the greatest
latitudinal distribution in Europe of the post 1950
introduced exotics. It is considered to be a weed
throughout much of its European native range. It is
naturalized in eastern U.S., Canada, and New Zealand.
Although invasive of some regions oregano is not
regulated.
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Peganum harmala
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African rue was found in
northeast Montana during the mid-1980s. Six western
states have designated it as a noxious weed, the most
northerly being Oregon. It is invasive of semiarid
grasslands and shrublands. It is a problem plant in
Europe, China, as well as Africa. Toney et al. (1998)
ranked it as invasive of the Pacific Northwest.
Australia prohibits the import of African rue.
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Pimpinella saxifraga
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Solidstem burnet saxifrage has
two occurrence records in the Pacific Northwest. It is a
weed in the northeastern U.S. and eastern Canada. It is
not regulated.
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Rhamnus frangula
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Tall buckhorn is considered to
be locally invasive and spreading in eastern Canada and
northeast U.S. Manitoba designates it as a noxious weed.
There is only one Pacific Northwest record and it lacks
site information. European buckthorn (Rhamnus
cathartica) is widely established in the Montana and
clearly invasive.
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Rorippa austriaca
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Austrian fieldcress is a
rhizomatous perennial mustard with a northerly
distribution in North America. Five western states have
declared it a noxious weed. Toney et al. (1998) ranked
it as invasive of the Pacific Northwest. Known to be a
weed in Europe and Japan. Australian prohibits it
import.
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Salsola collina
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Slender Russian thistle is
found throughout the Great Plains of the U.S. and Canada
but is mostly likely under reported because it is often
judged to be a variant of prickly Russian thistle
(Salsola tragus or S. iberica). Specialists expect the
abundance and geographic distribution of slender Russian
thistle to continue to increase in coming decades.
California and Colorado are the only states that
currently list it as noxious.
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Scorzonera hispanica
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Black salsify has only been
reported as naturalized in California and Japan.
Otherwise it is only considered to be a garden weed.
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Senecio mikanioides
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German or cape ivy has been called the
kudzu of the west because of the invasive and
dominating growth of this woody vine in California. The
accepted scientific name is now Delairea odorata. The
single Pacific Northwest record (Richland County,
Montana, 1976) has no site information. California has
not listed this weed as noxious. The IUCN Invasive
Species Group has included Delairea odorata in its list
of the world's 300 worst invasive species.
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Vulpia myuros
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Rattail fescue is the most
widespread and abundant annual grass in California. It
often is the dominant on dry disturbed sites. Its known
Pacific Northwest distribution includes British
Columbia, Oregon, Washington, western Idaho, and
Montana. Subsequent to the model construction we
determined that it was present in Gallatin County,
Montana as early as 1946. It is a recognized weed in
Australia, South America, South Africa, Japan, and
Europe. Like most weedy annual grasses it is not listed
as noxious anywhere in North America
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