Vulpia myuros
(annual fescue)

Vulpia myuros is an annual grass, native to much of Europe and parts of Asia, introduced to the USA, Australia and a number of other countries, and reported as invasive in Australia, the western USA and parts of the Pacific. It outcompetes native species in grasslands of the western US and is a significant agricultural weed. It forms dense swards and its shallow roots suppress growth of native grasses and forbs. Establishment of native plants is strongly hindered once it has become dominant; because it is a winter-annual, it grows rapidly in early spring, thus successfully competing with the slower-growing native perennial grasses. It is a problem weed in pastures and in direct-seed cropping systems. Infested hay can cause injury to livestock due to the sharp seeds. Seeds easily attach to animals and cause losses in the wool industry. Residues of degrading Vulpia plants affect growth of other species including crops.

The native range of V. myuros is Eurasian and has certainly been enlarged under human influence. For example, it spreads easily along railways (Cotton and Stace, 1977). It is widespread throughout southern and Central Europe; the range extends east to north-western India and parts of China.

The species is found in most US states. In California and Oregon in particular, it has become an important component of annual grasslands, mainly in California's Central Valley and the South Coast Ranges of California and Oregon (Howard, 2006); according to CAL-IPC (2005) it is found throughout California except possibly the Great Basin region.

In Australia, the current range includes large tracts in the southwestern and southeastern part of the continent including Tasmania (Wallace, 1997). The grass is found between 25° S and 44° S (Wallace, 1997).

Seeds attach to animals and clothes and can easily be moved by livestock, people or machinery. If they are a component of seed mixtures used for revegetation programmes, the grass may be introduced in large quantities to new areas. Vulpiamyuros is a prolific seeder and accumulates a soil seed bank; soil movement may contribute to its spread. (A risk assessment, adapted for Florida, is provided by PIER (2014)).

In its native range, V. myuros commonly grows in dry ruderal sites, on sand and gravel banks, roadsides and embankments, and in old fields, usually on acidic soils.

In the West Coast states of the USA, V. myuros is an important component of annual grasslands; it is also reported from a wide range of habitats subjected to disturbance, for example fires, soil degradation, abandonment of cultivated fields and logging (Howard 2006). It is an important groundlayer component in western hardwoods, especially in oak woodland, although it is most common in early successions, tends to decrease with canopy closure in woodlands, and does not persist in closed forests (Howard 2006). It forms part of the groundlayer flora in non-native bluegum woodland (Eucalyptusglobulus). It occurs in montane chaparral with Ceanothuscuneatus as the dominant shrub (Howard, 2006). In California it also grows at the edges of vernal pools (Howard, 2006), ephemeral water bodies harbouring a highly specialized flora. In northwestern Oregon, it invades broadleaved forests with bigleaf maple (Acermacrophyllum) and associated shrubs (Bailey and Poulton, 1968).

In the eastern and southeastern USA, V. myuros is found mainly in disturbed sites, e.g. roadsides, fields and waste places (Wunderlin, 1998).

In Australia, it is found in waste places, native and sown pastures and sheep camps (Wallace, 1997).

V.myuros is a weed in direct-seeded cropping systems, especially wheat (Wallace, 1997; Ball et al., 2008). Due to allelopathic compounds and toxic residues of decaying plants, it affects germination and growth of other crops including perennial legumes and grasses. Together with other annual grasses of Eurasian origin, it locally outcompetes native perennial grasses in the western USA including Elymusglaucus, Hordeumbrachyantherum, Koeleriacristata, Melicacalifornica, and Nassellapulchra (Brown and Rice, 2000).

Genetics

V.myuros is a hexaploid species with a chromosome number of 2n = 42 (Cotton and Stace, 1977; Hickman, 1993).

Natural hybrids between V.myuros and Festucarubra have been reported in the British Isles (Ainscough et al., 1986), the Czech Republic (Krahulec and Nesvadbova, 2007), and Italy (Ardenghi et al., 2011). Hybrids with Festuca nigrescens have also been reported in the British Isles (Ainscough et al., 1986). Due to the cleistogamous flowers of Vulpia, such hybrids are rare and it has been suggested that they result from Festuca pollen reaching the stigmas of Vulpia flowers (Ainscough et al., 1986). Hybrid populations consist largely of sterile plants (Ainscough et al. 1986).

Reproductive Biology

Flowers of V.myuros are cleistogamous, i.e. non-opening and self-pollinating (Lonard and Gould, 1974). As an annual, the species reproduces by seed only. Seed weight is 0.5-0.6 mg (Wallace, 1997). Seed production can be prolific under favorable conditions and seed rain may reach 265 000 seeds m^-2 (Dowling, 1996). The species forms a large soil seed bank (Bartolome, 1979; Wallace, 1997). Little is known on the longevity of seeds in the soil, although Wallace (1997) states that they remain viable for at least 3 years. Seeds dry- stored for two years germinated well (Buhler and Hoffmann, 1999), suggesting that the species accumulates at least a short-term seed bank.

Germination rates are usually high and seeds do not require scarification, but they do require an after-ripening period of 2-3 months (Buhler and Hoffmann, 1999; DiTomaso and Healy, 2007). Ball et al. (2008) give an after-ripening period of 1-12 months. After that, seeds germinate whenever conditions become favourable. Thus, fresh seeds collected near Davis, California, in June had germination rates of 2% or less whereas in August nearly 98% germinated (Laude, 1956). Buried seeds do not germinate well (Wallace, 1997), although germination can take place both under light and dark conditions (Dillon and Forcella, 1984). Deeply buried seeds fail to germinate unless disturbances bring them to the soil surface (Howard, 2006). Jensen (2009) found variable effects of burial depth on germination.

Glasshouse studies have found that germination rates at moderate temperatures (15-20° C) are higher than at high temperatures (23-28° C), but germination is complex and depends on the interplay of temperature, time of year, light conditions and water status (Wallace, 1997; Ball et al., 2008).

Under field conditions, seeds require an autumn rainfall of at least 13 mm (California – Howard, 2006) or a monthly rainfall of at least 50 mm (Australia – Wallace, 1997) to germinate.

Physiology and Phenology

V.myuros is a winter annual. Seeds germinate following sufficient rainfall in early spring. Most seedlings appear between March and early June in Australia (Wallace, 1997); in California, most germination occurs in autumn and early winter (DiTomaso and Healy, 2007). Growth rates are highest in the first 2-4 months but depend on temperatures (Wallace, 1997). Depending on growing conditions, it takes 7-30 days from flowering to seed maturity (Wallace, 1997). In Australia, seeds are typically shed in October to November (Scott, 1990). In California, most plants have dried and died by early May (Howard, 2006).

Longevity

Vulpiamyuros is an annual. It survives adverse conditions (high summer temperatures, drought) as seeds (Wallace, 1997). The culms may die back and the grass sprout from the root crown when wet weather follows a short dry period during the growing season (Hyder and Bement, 1964).

Population Size and Structure

Since V.myuros is an annual, population density and sizes are variable from year to year, and depend on the habitat type and on the amount of precipitation received during the growing season.

In Australian pastures, up to 43 000 seedlings m^-2 have been observed (Scott and Blair, 1987); in a Californian site seedling density was locally more than 200 000 seedlings m^-2 (Howard, 2006). Cover ranges from 9-17% in sites of the Californian Central Valley but may reach much higher values (Howard, 2006). Disturbances generally lead to an increase of Vulpia cover (Howard, 2006).

Associations

In Europe, Vulpiamyuros is associated with ruderal species, heather (Callunavulgaris), and other annual grasses, e.g. Bromus sp. In Australian pastures, plants most frequently associated with V. myuros are broadleaved annuals (e.g. Trifoliumsubterraneum, Arctothecacalendula, Erodium sp.) and other annual grasses, e.g. Loliumrigidum, Hordeum sp., Bromus sp. (Wallace, 1997). In Californian annual grasslands, V. myuros is most commonly associated with red brome (Bromusrubens) and filarees (Erodium sp.), especially on thin, sandy soils (Howard, 2006).

Environmental Requirements

V. myuros is a winter annual and grows best in climates with cool winters and warm summers. Plants are sensitive to drought due to their shallow roots (Wallace, 1997; Tarasoff et al., 2013). It tolerates a wide range of soils, but not drought (Wallace, 1997). It grows well on soils of low to intermediate phosphorus status and tolerates soils with low potassium (Wallace, 1997).

In Australia V. myuros grows in areas with 200-1200 mm annual rainfall. Altitudinal ranges vary from region to region. In the Kashmir Himalaya, it grows at 1800-3200 m (Khuroo et al., 2007), in South Africa at 100-2900 m (POSA, 2013), in Mexico up to 1700 m (Howard, 2006), and in California from coastal areas up to 2000 m (Howard, 2006). In the northern tablelands of New South Wales, Australia, it is found above 1000 m (Wallace, 1997).

The British Mycological Society (2014) lists two fungal species as associated with V. myuros, although it does not state that they are pathogenic: Puccinia hordei and P. recondita (Basidiomycota: Pucciniales).

Environmental

• Erosion control or dune stabilization
• Revegetation

Brome fescue (Vulpia bromoides (L.) Gray), another annual in this genus, is of similar appearance. It can be distinguished from V. myuros by its lower glume, which is 2.5-5 mm long, and its spikelets containing 4-7 florets (Wallace, 1997; Hickman, 1993).

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.

Cultural Control

Tozer et al. (2010) found that oversowing with clover reduced the abundance and fecundity of deliberately sown V. myuros and Bromus hordaceus in pasture plots in New Zealand.

Physical/Mechanical Control

Residues of V.myuros in the soil can be managed by strategic use of autumn burning (Pratley and Ingrey, 1990). Spring fires can kill the species, and fire in any season may reduce its seed bank because of subsequent germination (Davis et al., 1989). The long-term effects of fires on Vulpia cover are unclear; studies have shown an increase after prescribed burning, a decrease, or no effect (Dunne et al., 1991; Howard 2006). Howard (2006) states that fire has limited use in controlling V.myuros.

Vulpia does not tolerate cultivation because buried seeds do not germinate (Wallace, 1997).

Hand-pulling is recommended for small infestations in sensitive habitats such as vernal pools (Gillespie and Allen, 2004).

Chemical Control

V.myuros is susceptible to simazine applied in autumn (Wallace, 1997). The effective rate of herbicide will depend on rainfall regime and soil type (Stephenson, 1990). Other herbicides used for V.myuros include propyzamide, carbetamide, dalapon, a mixture of chlorsulfuron plus trifluralin, or paraquat (Wallace, 1997; Jemmett et al., 2008). a mixture of S-metolachlor and prosulfocarb (Hashem et al, 2012). Hull et al. (2011) found that flufenacet and prosulfocarb were the most effective pre-emergence herbicides and acetolactate-synthase-inhibiting herbicides were the most effective post-emergence; acetyl-coenzyme-A-carboxylase-inhibiting herbicicdes were not effective.

A widely used method is spray-topping, where non-selective herbicides such as glyphosate are applied to seed heads during flowering. This prevents viable seed set (Wallace, 1997).

Grazing

Vulpia sp. can persist under heavy grazing (Wallace, 1997), but a combination of heavy grazing in spring and autumn reduced its density by 91–97% (Wallace 1997). In contrast, it increases under moderate to heavy grazing in Californian annual rangelands (Howard, 2006). A study by Tozer and Chapman (2012) suggested that rotational grazing, causing a combination of severe shading and defoliation, could suppress Vulpia species to a greater extent than in continuously grazed pastures.

Little is known on the invasive behavior of V.myuros in the deserts of the southwestern USA. Detailed studies documenting its ecological impacts are lacking for; most studies state changes in cover or density over time. More research is needed to understand the mechanisms of how the species interferes with native plants in valuable habitats such as vernal pools or native perennial grasslands of the Pacific Northwest.

USA: California Invasive Plant Council (Cal-IPC), 1442-A Walnut Street, #462, Berkeley, California, CA 94709, http://www.cal-ipc.org/

03/06/2013: Original text by:

Ewald Weber, Biodiversity Research, University of Potsdam, Maulbeerallee 1, D-14469 Potsdam, Germany