Ventenata dubia
(North Africa grass)

Pictures

Picture	Title	Caption	Copyright
Title Invasive habit Caption Ventenata dubia (North Africa grass); invasive habit. This species forms dense stands, much like other annual colonizing grass species. Bozeman, Montana, USA. July, 2008. Copyright ©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0	Invasive habit	Ventenata dubia (North Africa grass); invasive habit. This species forms dense stands, much like other annual colonizing grass species. Bozeman, Montana, USA. July, 2008.	©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0
Title Invasive habit Caption Ventenata dubia (North Africa grass); invasive habit, colonising disturbed sites in open dry areas. The long, naked, staight and wiry inflorescences branches diverging at right angles are distinguishing characteristics of the species. USA. September, 2011. Copyright ©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0	Invasive habit	Ventenata dubia (North Africa grass); invasive habit, colonising disturbed sites in open dry areas. The long, naked, staight and wiry inflorescences branches diverging at right angles are distinguishing characteristics of the species. USA. September, 2011.	©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0
Title Pulled plant Caption Ventenata dubia (North Africa grass); pulled plant. The long branches are stiff and wiry and mostly devoid of spikelets, which renders one of the common names 'wiregrass'. Bozeman, Montana, USA. July, 2008. Copyright ©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0	Pulled plant	Ventenata dubia (North Africa grass); pulled plant. The long branches are stiff and wiry and mostly devoid of spikelets, which renders one of the common names 'wiregrass'. Bozeman, Montana, USA. July, 2008.	©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0
Title Inflorescence branches Caption Ventenata dubia (North Africa grass); Vententata colonizes disturbed sites in open dry areas. The long, naked, straight and wiry inflorescence branches diverging at right angles are distinguishing. Nr. Boise, Idaho. September, 2011. Copyright ©Prof Matt Lavin-2009/Bozeman, Montana, USA - CC BY-SA 2.0	Inflorescence branches	Ventenata dubia (North Africa grass); Vententata colonizes disturbed sites in open dry areas. The long, naked, straight and wiry inflorescence branches diverging at right angles are distinguishing. Nr. Boise, Idaho. September, 2011.	©Prof Matt Lavin-2009/Bozeman, Montana, USA - CC BY-SA 2.0
Title Glumes Caption Ventenata dubia (North Africa grass); seeds. The distinctly ribbed glumes and two florets per spikelet, where the upper is long-awned and disarticulates, are distinctive of this species. Bozeman, Montana, USA. September, 2008. Copyright ©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0	Glumes	Ventenata dubia (North Africa grass); seeds. The distinctly ribbed glumes and two florets per spikelet, where the upper is long-awned and disarticulates, are distinctive of this species. Bozeman, Montana, USA. September, 2008.	©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0
Title Glumes Caption Ventenata dubia (North Africa grass); seeds. The distinctly ribbed glumes and two florets per spikelet, where the upper is long-awned and disarticulates, are distinctive of this species. Bozeman, Montana, USA. September, 2008. Copyright ©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0	Glumes	Ventenata dubia (North Africa grass); seeds. The distinctly ribbed glumes and two florets per spikelet, where the upper is long-awned and disarticulates, are distinctive of this species. Bozeman, Montana, USA. September, 2008.	©Prof Matt Lavin-2008/Bozeman, Montana, USA - CC BY-SA 2.0

Identity

Preferred Scientific Name

• Ventenata dubia (Leers) Coss. & Durieu

Preferred Common Name

• North Africa grass

Other Scientific Names

• Avena dubia Leers
• Avena fertilis All.
• Avena triaristata Vill.
• Festuca tenuis (Moench) Raspail
• Gaudinia tenuis (Moench) Trin.
• Heteranthus dubius (Leers) Thell.
• Heteranthus tenuis (Moench) Dumort.
• Trisetaria tenuis (Host) Baumg.
• Trisetum tenue (Moench) Roem. & Schult.
• Ventenata avenacea Koeler
• Ventenata bromoides Koeler

International Common Names

• English: hairgrass; North Africa grass; softbearded oat grass; wiregrass
• French: venténata fausse-avoine; venténate douteuse; venténatée douteuse

Local Common Names

• Germany: Schmielenhafer

Summary of Invasiveness

Ventenata dubia, commonly known as North Africa grass or wiregrass, is an annual grass native to Europe and North Africa. It is shallow-rooted, with narrow leaf blades, and has been able to invade both annual-dominated and perennial-dominated grasslands. Grasslands previously dominated by Taeniatherum caput-medusae and Bromus tectorum are being invaded and dominated by V. dubia in the USA, where it is considered a weed. Pasture and grass hay production systems have been dominated by V. dubia within the Pacific Northwest, USA, and it has invaded sagebrush-steppe communities. Estimated losses for pasture and grass hay in northern Idaho and eastern Washington state, USA, is over $20 million annually.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Poaceae
•                             Genus: Ventenata
•                                 Species: Ventenata dubia

Notes on Taxonomy and Nomenclature

The genus name, Ventenata, is associated with French botanist Pierre Ventenat (1757-1805) (Nature Conservancy, 2000). The genus was previously placed within the Avena genus (subtribe Aveninae) and resides within the subtribe Airinae.

There are eight species in the genus Ventenata (The Plant List, 2013): V. blanchei Boiss., V. dubia (Leers) Coss. & Durieu, V. eigiana (H. Scholz & Raus) Dogan, V. huber-morathii (Dogan) D. Heller, V. macra (Steven) Balansa ex Boiss., V. quercetorum Boiss. & Bal., V. sorgerae (Dogan) D. Heller, and V. subenervis Boiss. & Balansa.

V. dubia is often referred to as wiregrass because its hardened stems can become tangled around the swather of a mowing machine (Scheinost et al., 2008).

Description

V. dubia is a tufted winter annual grass with shallow fibrous roots. The stem is erect, 1.5-7 dm, and appears smooth, although tiny hairs can be seen when magnified. The leaf ligule is 1-6 mm long and the blade is 1-3 mm wide. Inflorescences are tawny to pale yellow, open, panicle-like, 3-10 cm long. The branches often spread until they droop. Spikelets (10-15 mm long) are near the branch tips and are stalked. The glumes are lancelolate, and end in a sharp tip. The lemmas have bent awns arising from their backs, much like those of wild oats (Avena barbata, A. fatua). The upper 1-2 florets are bisexual. Adapted from Nature Conservancy (2000) and Hitchcock (1969).

Distribution

Native and introduced ranges are challenging to determine for a species like V. dubia that has not received much study.  Many entries within the distribution list are from specimens which would not specify whether it is native or introduced. V. dubia is generally considered native to Europe, however, V. dubia in Essex, UK, has been reported as an introduced and invasive species (Copping, 1987). Generally it is considered rare and native in eastern Europe. Outside of Europe, it is considered native to Tunisia, Iran and Turkey.

V. dubia has been introduced widely across North America (BONAP, 2015), to states such as California, New York and Washington (BONAP, 2015; IUCN, 2015; USDA-NRCS, 2015). In Canada, it has also been introduced to Alberta, British Columbia, New Brunswick, Ontario and Quebec (Douglas et al., 1998; Newmaster et al., 1998; Hinds, 2000; Flora of North America Editorial Committee, 2007; Lavoie et al., 2012).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Risk of Introduction

V. dubia can be introduced via seed contamination, particularly in the USA where it is not subject to seed laws.  

V. dubia can be found as a contaminant in Kentucky bluegrass, hay and annual crops (Sheinost et al., 2008).

Asian markets do not accept it as a contaminant in grass hay; therefore grass hay contaminated with V. dubia cannot be exported. 

Habitat

V. dubia is found in annual and perennial grassland in US states such as Washington, Idaho and Oregon (Prather, 2014). It can also be found in sagebrush-steppe communities throughout the western US (Bansal et al., 2014).

Habitat List

Growth Stages

Biology and Ecology

Genetics

V. dubia is a diploid species with a chromosome number of 2n=14.

Physiology and Phenology

V. dubia flowers from June to August with 2 or 3 fertile florets per spikelet, according to The Nature Conservancy (2000) which describes American flora. Spikelets break up quickly after maturity and the lowest floret retains the glumes.

Germination takes place above 8°C when there is approximately 1.8 cm of precipitation (silt loam soil texture). In western North America, most germination occurs in autumn with a small percentage (less than 15%) of seedlings germinating in late winter and spring. The after-ripening requirement is longer than 30 days and less than 60 days. Cold stratification reduced germination from 87% when stored at 20°C, dropping to 28% and 35% when stored at 5°C for 5 or 10 days respectively. Using a base temperature of 7°C, emergence took place at 50 to 130 growing degree days (GDD). Emergence was affected by land use, with perennial grasslands in the Conservation Reserve Program and in timothy hay having shorter GDD. Rangeland was longer at 130 GDD. Stem elongation began at approximately 320 to 360 GDD and anthesis initiated after 360 to 500 GDD (Wallace at al., 2015).

Climate

Latitude/Altitude Ranges

Air Temperature

Rainfall

Natural enemies

Notes on Natural Enemies

V. dubia is rated as ‘least concern’ by the IUCN since it has no major threats at present (IUCN, 2015).

V. dubia is unpalatable to livestock once the stems harden after the panicles begin to emerge (Sheinost et al., 2008).

Means of Movement and Dispersal

Accidental Introduction

Within western North America, the primary pattern for dispersal is along roadways and trails (Lass and Prather, 2007). Dispersal likely is on vehicles since seeds are small and the pattern of dispersal is from road edge to adjacent lands (T Prather, University of Idaho, USA, personal communication, 2015).

Often the first places V. dubia is found is within areas that are saturated with water, typically because of an underlying restricted infiltration layer, for part of the spring (Anicito, 2013). V. dubia has been found as a contaminant in both hay fields and in grass fields grown for seed (Old and Callihan, 1987).

The long awns on its seed allow it to be spread by becoming attached to animals (Sheinost et al., 2008) and potentially vehicles and machinery.

Impact Summary

Economic Impact

In inland northwestern USA, V. dubia has resulted in the reduction of both grass hay production and grass stand life by as much as 50% and foreign export of infested hay is not possible. Overall yields are 20% lower because of V. dubia. Therefore farmers have had to change their practices and are trying various methods of control. Regional losses (in eastern Washington and northern Idaho, USA) are $6.7 million and ripple effects in the economy pose a $22 million negative impact (Prather, 2014).

V. dubia has a shallow root system which may make soil more susceptible to erosion. Its invasion leads to a decline in productivity and land value (Sheinost, 2008).

In Canada and the lower 48 states of the USA, V. dubia is considered a weed (Whitson et al., 1996).

Environmental Impact

Impact on Biodiversity

V. dubia changed plant species composition within Conservation Reserve Program lands (CRP - a land conservation programme administered by the Farming Service Agency) when it made up more than 50% foliar cover. The plant community change then resulted in changes to insect abundance during the nesting period of swallows that were foraging within CRP. Furthermore, reproduction of tree swallows was lower in areas with more than 50% foliar cover of V. dubia compared to areas with less than 10% foliar cover of V. dubia (Mackey, 2014).

Within its current distribution in northern Idaho and eastern Washington, USA, V. dubia has largely replaced cheatgrass (Bromus tectorum) as the dominant annual grass. In Oregon, where distribution overlaps with medusahead (Taeniatherum caput-medusae), V. dubia has become the dominant plant in many instances.

Risk and Impact Factors

• Proved invasive outside its native range
• Highly adaptable to different environments
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
• Pioneering in disturbed areas
• Tolerant of shade
• Highly mobile locally
• Benefits from human association (i.e. it is a human commensal)
• Has propagules that can remain viable for more than one year

• Altered trophic level
• Changed gene pool/ selective loss of genotypes
• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Monoculture formation
• Negatively impacts agriculture
• Negatively impacts cultural/traditional practices
• Negatively impacts forestry
• Negatively impacts animal health
• Negatively impacts livelihoods
• Reduced amenity values
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species
• Damages animal/plant products

• Antagonistic (micro-organisms)
• Competition - monopolizing resources
• Competition - shading
• Pest and disease transmission
• Herbivory/grazing/browsing
• Interaction with other invasive species

• Highly likely to be transported internationally accidentally
• Difficult to identify/detect as a commodity contaminant
• Difficult to identify/detect in the field

Uses

Economic Value

V. dubia has little value as a forage plant since it becomes unpalatable to livestock once the stems harden after the panicles begin to emerge (Sheinost et al., 2008).

Similarities to Other Species/Conditions

Before seed formation, V. dubia looks very similar to Deschampsiacespitosa, and other Deschampsia species. The length of the ligule overlaps 2-13 mm for D. cespitosa, 1-8 mm for V. dubia. Both have narrow leaves; 1-4 mm vs 0.8-2.5 mm for D. cespitosa and V. dubia respectively. Generally, V.dubia has purple to reddish brown culm nodes. When flowers are present, both have awns; upper awns of V. dubia are geniculate but the awn of the first floret is not geniculate, so if the other florets are no longer on the plant it may be confused with D. cespitosa. The rachilla of D. cespitosa is hairy, generally glabrous in V. dubia.

Another similar species is P. bulbosa, which has purple to reddish brown nodes on the culms but the keeled leaf tip should prevent confusion on closer examination.

The Nature Conservancy (2000) describes V. dubia in relation to flora in the USA and note that it can be mistaken for the annual cheatgrass (Bromus tectorum) due to shared characteristics of open panicles and similar height. However, B. tectorum has awns which are straight rather than bent, 3-6 florets per spikelet rather than 2-3 and flowers earlier, from May to June.

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Control

Physical/mechanical control

It may be possible to eliminate or severely reduce and infestation of V. dubia via three to four years of aggressive management, followed by monitoring, since the seed is viable for only one to three years (Sheinost et al., 2008; Pavek et al., 2011).

Mowing V. dubia multiple times before heading, until the soil is dry and V. dubia cannot grow, may prevent seed from being produced. However, once heads are present it is too difficult to mow since the stems are too tough and simply bend (Sheinost et al., 2008).

Chemical control

V. dubia has shown resistence against glyphosphate and sethoxydim but imazapic appears to be effective (Nature Conservancy, 2000; Scheinost et al., 2008).

Cultural control and sanitary measures

Maintaining a healthy stand of perennial vegetation can minimize invasion by V. dubia (Scheinost et al., 2008).

Control by utilization

Animals will not eat V. dubia directly but some reports say that animals eat it when in small amounts in hay.

Gaps in Knowledge/Research Needs

Genetic analysis is required to determine native and introduced distributions.

References

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Links to Websites

Contributors

21/05/2015 Original text by:

Timothy Prather, University of Idaho, USA

Distribution Maps