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Weed Alert!

Ventenata dubia (Leers) Durieu.
(wiregrass, hairgrass)


Summary: new plant of unknown characters
Ventenata dubia has established itself in a number of states in the USA and provinces in Canada. It is currently expanding from Washington and Idaho to the Idaho-Nevada border near Duck Valley. It invaded Utah in 1996. Its expansion in the Pacific Northwest will probably continue via transportation as a contaminant in grass seed.

Description:
(Click on thumbnail images for a closer view)

Plant features

Infestation

Ventenata dubia (Leers) Durieu. is an introduced tufted annual grass. The stem is erect, 1.5-7 dm, and appears smooth, although tiny hairs are noticeable when magnified. The leaf ligule is 1-6 mm long and the blade is 1-3 mm wide. Inflorescences are panicle-like, 3-10 cm long and open. 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.

V. dubia is similar in appearance to Bromus tectorum (cheatgrass). Both grasses are annuals, similar in height and have open panicles. V. dubia spikelets are much like those of Avena, with bent awns, 2-3 florets per spikelet and larger glumes ending in a sharp tip. In contrast, B. tectorum has straight awns, 3-6 florets per spikelet, and smaller glumes. V. dubia flowers from June to August, while B. tectorum flowers earlier in the year, from May to June.

V. dubia germinates best at moderate to high temperatures. An experiment at different temperatures found 24%, 93%, and 50% germination at 8, 18, and 28C respectively; the number of days to achieve 75% germination was 6 days at 18C, 10 days at 28C, and 13 days at 8C (Northham & Callihan, 1986). In Wisconsin, V. dubia plants were near-flowering on June 14, and by July 5 all plants had produced mature fruit and died (Solheim & Judziewicz, 1984).

Scientific and Common Names:
The generic name Ventenata honors the french botanist Pierre Ventenat (1757-1805). The common names "wiregrass" and "hairgrass" describe the plant's form.

Impacts and Considerations:
The impacts of this new invader are unknown. However, V. dubia has the following characteristics:
1)It is weedy in disturbed areas such as alongside roads and in fields.
2)It is highly invasive in bluegrass, alfalfa, winter wheat, pasture and rangeland.
3)It can impede mechanical harvesting equipment.

Native Range:
Ventenata dubia is native to central and southern Europe, Asia, and Africa.

Range As An Invader:
Ventenata dubia has been found in California (Siskiyou Co., southern Nevada Co., at 1200-1500 m elevation), Idaho, Montana (Mineral Co.), Nevada, Oregon (Polk Co.), Utah (Elmore Co.), Washington, and Wisconsin (Oconto Co.). In Canada it has been found in Ontario, Quebec (Missiquoi Co.) and British Columbia. While many papers cite the first North American record of V. dubia as being a 1964 Idaho collection by Baker, Old & Callihan (1987) state the first occurrence was in Idaho in 1957. Some authors (Malone, 1999; Allen & Curto, 1996) maintain that V. dubia has not been found in Nevada (but cf. Old & Callihan, 1987). Expansion in the Pacific Northwest will no doubt continue, and may be accelerated by its spread as a contaminant in crop grasses grown for seed.

Control:
Control methods have not been developed for this relatively new invader.
1)It is an annual, so the focus must be on reducing or stopping seed production.
2)V. dubia has demonstrated resistance to glyphosate and sethoxydim.
3)Mowing may be ineffective since this grass tends to bend rather than cut.
4)Palatability is low and so grazing may not be an option.

References:
1)Allen, L. and M. Curto. 1996. Noteworthy Collections - Utah. Madrono vol. 43:337-338.
2)Chambers, K.L. 1985. Pitfalls in Identifying Ventenata dubia (Poaceae). Madrono, vol. 32, no. 2:120.
3)Hickman J.C., ed. 1993. The Jepson Manual, p. 1302. University of California Press, Berkeley.
4)Malone C. 1999. Another Weed. Northern Nevada Native Plant Society Newsletter vol. 25, no. 2:1-2.
5)Northam, F.E. and R.H. Callihan. 1986. Germination of four annual grass weeds at three temperatures. Proceedings of the Western Society of Weed Science, vol. 39:173.
6)Old, R.R. and R.H. Callihan. 1987. Ventenata dubia in the Pacific Northwest. Proceedings of the Western Society of Weed Science, vol. 40:130.
7)Solheim, S.L. and E.J. Judziewicz. 1984. Four noteworthy Wisconsin plants. Phytologia, vol. 54, no. 7.
8)NHIC List of Ontario Vascular Plants (http://www.mnr.gov.on.ca/MNR/nhic/lists/vascular.html)
9)Watson, L. and Dallwitz, M. J. 1992 onwards, Grass Genera of the World: Ventenata

--Tunyalee Martin/Wildland Invasive Species Team; January 2000



Updated September 2005
©The Nature Conservancy, 2000