Agrostis capillaris
(common bent)

Common bent, Agrostis capillaris, is a typical and often abundant species in grasslands on acidic or neutral soils. It is native and widespread throughout most parts of Europe, western and southwestern Asia and North Africa. Within its native range the species is often abundant in nutrient poor pastures, along roadsides or on disturbed ground. A. capillaris has been intentionally introduced as a pasture grass and as a turf grass for lawns, in particular for golf courses, into a number of countries and has become widespread in North America, Australia, New Zealand and parts of South America. It has been recorded as invading native grasslands in part of its exotic range, including prairies in North America.

A. capillaris is native to most of Eurasia, from Ireland and Britain in the west, through Siberia and Central Asia, as far east as China and from Scandinavia south to the Mediterranean, including Tunisia in North Africa. It has been introduced and has naturalized in the Americas (USA, Canada, Greenland, Brazil, Argentina and Chile), southern Africa, Australia and New Zealand (USDA-ARS, 2016). It has also been introduced to several islands, including Saint Helena, Hawaii, South Georgia and the South Sandwich Islands (GISD, 2016).

A. capillaris is widespread largely in the western and eastern sides of North America and is considered invasive in the northeastern and western states of the USA (GoBotany, 2016; USDA-NRCS, 2016).

In Australia, A. capillaris is widely naturalized in the wetter parts of southern Australia, in much of New South Wales, Victoria,Tasmania, southeastern South Australia and the coastal districts of southwestern Western Australia (Queensland Government, 2016).

In New Zealand it has been naturalized since the 1840s and is now extremely widespread (Thomson, 1922) as it is an important fodder plant of dryland pastures (Levy, 1924). However, it has a significant role in the degradation of native grasslands (Treskonova, 1991).

On a global scale, A. capillaris has colonised many of the the temperate geographical regions which can provide a suitable climate for its growth and development. Until recently, seed of A. capillaris has been intentionally imported for turf and pasture grass use into a number of countries under legal licensing procedures. It is likely that this form of introduction will continue to a certain degree, particularly when the species is already widespread in the importing country. 

A. capillaris mainly occurs in grasslands and pastures throughout its native and introduced ranges though the species can become adapted to a wide range of other habitats (Acheroy and Lefèbvre, 1983). It can be particularly dominant on poor and acidic soils and is well adapted to grazing pressure (Stace, 1997; Wörz, 1998; Bond et al., 2007; Gateley, 2015). It also invades ruderal, disturbed areas, heathland, woodland, scrub and sand dune habitats, as well as urban areas where it frequently colonizes roadsides (Rapson and Wilson, 1988; Gateley, 2015). A. capillaris can also become abundant in wetlands and cultivated areas (Garry Oak Ecosystems Recovery Team, 2016). In Australia, it is also reported from dry coastal vegetation, heathy woodlands, lowland grasslands, grassy woodlands, dry and damp sclerophyll forests, riparian vegetation and alpine and sub-alpine vegetation, including montane peatlands and swamps.

A. capillaris has not been reported as a weed in specific cropping situations, but can invade pastures and other grasslands. 

Genetics

Common bent forms hybrids with creeping bentgrass, A. stolonifera and black bent, A. gigantea (A. capillaris x gigantea= A. x bjoerkmanii Widén; Agrostis capillaris x stolonifera= A. x murbeckii Fouill.) (Tutin et al., 1980; NBN Gateway, 2016). EST sequence analyses by Rotter et al. (2007) showed that the allotetraploids (2n = 4x = 28) of A. capillaris and A. stolonifera had a genome, designated A₂, in common and that these A₂ genomes diverged from a common ancestor approximately 2.2 million years ago.

Reproductive Biology

A. capillaris is predominantly outcrossing. It is wind pollinated and propagates by seeds but also vegetatively by rhizomes and stolons (GISD, 2016). In some populations the high proportion of clones and low occurrence of seedlings indicate significant vegetative reproduction (Smith, 1972). In the northern hemisphere seed setting takes place from August to October (Grime et al., 1988). Seeds can persist in the soil seed bank for over 40 years (Thompson et al., 1997).

Physiology and Phenology

A. capillaris is a long-day C3 plant, with an active growth period starting in spring. The flowering panicle becomes evident from May and flowering continues into August in the northern hemisphere (Wörz, 1998; Gateley, 2015). Here anthesis occurs 2 weeks after first emergence of inflorescences (Philipson, 1937). In the southern hemisphere inflorescences emerge from December to January, with anthesis occurring about 3.5 weeks later. After seeds have been shed, the bare panicles usually persist all winter (Gateley, 2015).

A. capillaris adapts to environmental stresses genetically and through plasticity, resulting often in distinct locally adapted forms (Jowett, 1964; Wörz, 1998). Adaptive advantages caused by its high plasticity are considered to contribute to its invasiveness (Rapson and Wilson, 1992a, 1992b). On the other hand, there is very little evidence that A. capillaris develops distinctly adapted forms in its introduced range even after considerable time (Rapson and Wilson, 1988; Wilson and Rapson, 1995).

Associations

A. capillaris is often associated with Festuca rubra, which nevertheless prefers slightly richer (mesotrophic) soils (Peeters, 2015). Other species commonly associated with A. capillaris in Europe are Ranunculus acris, Leontodon hispidus, Nardus stricta, Anthoxanthum odoratum, Potentilla erecta and Plantago lanceolata (Wörz, 1998).

Environmental Requirements

Common bent has low climatic requirements, being very resistant to summer heat and winter cold. It is present in Atlantic and continental climates, at low and high altitude and, although it generally requires high light levels, can tolerate shade to a certain degree (Peeters, 2015).

Common bent is typical of mesotrophic to oligotrophic conditions and prefers fine to medium-textured soils containing a moderate level of organic matter, with a pH optimum of 6.5 to 7.3 (Dale et al., 1965). Optimal growth occurs on freely drained or fairly dry soils, but A. capillaris can also be abundant on poorly drained and damp soils when inhabiting wetlands (Rapson and Wilson, 1992a; Stace, 1997). Preferred soil conditions include sandy, schist, granitic and gneiss, where the soil reaction is acid, but also on chalk and dolomite with a basic soil reaction (Peeters, 2015). However, according to Wörz (1998), calcareous soil is only inhabited when the upper layer has become acidified.

The species is an indicator of low soil nutrient levels and often low phosphorus content (Wörz, 1998; Peeters, 2015). It lacks tolerance of magnesium, avoiding areas of higher magnesium concentration such as seashores (Wu, 1981), but has high tolerance of heavy metals and arsenic (Jowett, 1958, 1964; Wilson, 1988; Watkins and Macnair, 1991).

As well as grazing, A. capillaris tolerates cutting and mowing and also benefits from frequent burning (Briemle and Ellenberg, 1994; Wilson, 1999).

Several non-specific pathogens of A. capillaris have been recorded, some of which are thought to be specific to the genus Agrostis (Braun, 1995; Dennis, 1995; Ellis and Ellis, 1997; Buczacki and Harris, 1998; Legon et al., 2005; Spooner and Legon, 2006; BioInfo (UK), 2015). This is mirrored by a suite of arthropod herbivores feeding on A. capillaris, with numerous polyphagous Lepidoptera being recorded from this species (Emmet and Langmaid, 2002; Entopedia, 2015; Natural History Museum, 2016). Generally, the host specificity of Hemiptera recorded from A. capillaris or Agrostis is not entirely clear (see Southwood and Leston, 1959; Nickel and Remane, 2002) and it cannot be excluded that some species of this group are specifically adapted to A. capillaris. It is notable that in the UK, only one chrysomelid beetle has been recorded from A. capillaris (Cox, 2007). Equally, a range of herbivorous arthropod species, including Diptera, sawflies, aphids and other Hemiptera, has only been reported from the genus Agrostis, likely indicating difficulties in identifying the host species during field observations (Nickel and Remane, 2002; Pitkin et al., 2015).

In the northwestern USA, European crane fly larvae are the only insects reported to cause significant damage on common bent in most years (Cook, 2015). In this context the term European cranefly most likely refers to either Tipula paludosa Meigen or T. oleracea L., with all turf grasses in the USA reported to be susceptible to the larvae of these two species (Peck et al., 2006).

In its native range A. capillaris is recorded as a host of the hemiparasitic plant Rhinanthus serotinus (Ahonen et al., 2006).

Animal feed, fodder, forage

• Fodder/animal feed
• Forage

Environmental

• Amenity
• Erosion control or dune stabilization
• Landscape improvement
• Revegetation
• Soil conservation

Ornamental

• garden plant
• Seed trade

A. capillaris is a highly variable species with many cultivars recognized. Individual plants can differ greatly in size, habit, presence or absence of stolons or rhizomes, type of inflorescence and spikelet structure (GISD, 2016). There is wide phenotypic and genotypic variation in populations (Grime et al., 1988) and some of this variation may be the result of hybridization with A. stolonifera and A. castellana (Edgar and Forde, 1991).

Recent research suggests that much of what has been identified as A. capillaris in south-eastern Australia is actually highland bent (A. castellana), but implications for invasiveness and management are not clearly understood (Queensland Government, 2016). The most conclusive way to differentiate between the two species is to use vegetative characters. A. capillaris differs from A. castellana in having diffuse rather than clustered spikelets that are awnless, fewer rhizomes, divaricate panicle branches after anthesis, calluses that are glabrous or with hairs up to 0.1 mm long and glabrous lemmas. It also tends to flower somewhat earlier than A. castellana (Harvey, 2015). However, using spikelets primarily as a means of identification is inconclusive since field specimens of A. castellana often are found awnless as well. A. castellana is vigorously rhizomatous, has a longer ligule and has finer, rolled, grey-green leaves than A. capillaris (Batson, 1998; GISD, 2016).

A. capillaris differs from A. gigantea in its short ligules, especially on the vegetative shoots and the open panicles that lack spikelets near the base of the branches (Harvey, 2015).

A. capillaris is often confused with A. stolonifera (creeping bentgrass) and the two can form hybrids. Creeping bentgrass can be distinguished by its longer ligules (not coming to a point) and always having stolons. In addition, the panicle is open in A. capillaris and closed in A. stolonifera (Gateley, 2015; GISD, 2016; Garry Oak Ecosystems Recovery Team, 2016).

A. capillaris also readily hybridizes with A. vinealis, the hybrids being somewhat intermediate in morphology between the two parents (Harvey, 2015).

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 and Sanitary Measures

A. capillaris is highly adapted to grazing and tolerant of burning, so neither of these mechanisms can be used to control the species and can, in fact, result in increased abundance (Wilson, 1999; GISD, 2016). In cultivated areas, where A. capillaris can become a weed, short rotations with root crops may help reduce this species (Bond et al., 2007; GISD, 2016).

Physical/Mechanical Control

For Agrostis species in general, conventional control including physical removal is considered difficult or not feasible even when they exert a large negative impact on native biodiversity. However, for A. capillaris, mechanical removal by hand pulling, ploughing, grubbing and harrowing can reduce abundance. It can also prevent seeding when applied in spring or early summer before seed set (Morse and Palmer, 1925; Long, 1938). Manual removal is labour intensive and remaining pieces of broken stolons can re-establish (GISD, 2016).

Biological Control

There are no known biological control agents available for A. capillaris (Froude, 2002; GISD, 2016) and the value of the species worldwide as a commercial fodder and lawn grass may preclude any attempts at biological control.

Chemical Control

The graminicide cycloxydim has been used to effectively control A. capillaris in forest tree establishment situations (Clay et al., 2006). A. capillaris is also susceptible to the herbicides dalapon, hexazinone and sethoxydim, the last giving a 100% mean control rate (Evans, 1964; Hosaka, 1984; White et al., 1990), while glyphosate applied before emergence reduces growth rate (Salazar, 1982). The introduction of glyphosate resistance into A. capillaris by genetic engineering (USDA-APHIS, 2003) may have implications for the species’ invasiveness, spread and control.

29/02/2016 Original text by:

Norbert Maczey, CABI, Egham, UK