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  • Results •

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.



  • Alhagi maurorum •
        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 •
        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 •
        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 •
        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 •
        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 80’s. It has since been declared noxious in Alberta, Manitoba, and Minnesota.
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  • Crupina vulgaris •
        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 1980’s. 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 •
        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 •
        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 •
        Little is known about sharpleaf baby’s 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 •
        Showy baby’s 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 •
        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 •
        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 •
        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 •
        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 •
        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 •
        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 •
        Arkwright’s 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 1980’s, 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 •
        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 •
        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 •
        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 •
        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 •
        African rue was found in northeast Montana during the mid-1980’s. 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 •
        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 •
        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 •
        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 •
        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 •
        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 •
        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 •
        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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