Impact Assessment - Blue canary grass (Phalaris coerulescens) in Victoria
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Assessment of plant invasiveness is done by evaluating biological and ecological characteristics such as germination requirements, growth rate, competitive ability, reproduction methods and dispersal mechanisms. Assessment of plant impacts, however, is determined by the extent to which a plant affects a land manager’s environmental, economic and social resources.
The relative importance of these resources varies depending upon the value people place on them and, as such, the assessment process is subjective. For example, a farmer is likely to place a higher emphasis on the impact of a plant on production (economic resource) than its impact on areas of natural vegetation occurring on the farm. Conversely, a Landcare or Friends group would value environmental or social resources more than economic resources.
Recognising that the value of resources vary between different land tenures, plant impact assessments allow a prioritisation of resources by land managers. Assessments can apply at a local, regional or state level, and the relative values of each resource identified may differ at each level.
The impact assessment method used in the Victorian Pest Plant Prioritisation Process uses three broad resource categories: social, environmental and agricultural, each with a number of related attributes. For example, social resources include such attributes as how the plant affects human access for recreation, or if it creates a health risk due to toxicity or by producing allergens.
| Each resource attribute, or criterion, is assessed relative to a list of intensity ratings. Depending upon information found in relation to each criterion, a rating of Low, Medium Low, Medium High or High is assigned. Descriptions of the impact criteria and intensity ratings used in this process can be viewed here. |
The following table provides information on the impact of Blue canary grass.
A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:
Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1026 KB)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).
Common Name: Blue canary grass
Scientific name: Phalaris coerulescens
| Question | Comments | Rating | Confidence |
| Recreation | |||
| 1. Restrict human access? | The grass grows in tufts or clumps with tubers at base of stem generally above ground (Herbarium usu). The adult plant grows to heights of 30-150 cm tall (Davis, 1985; McLaren and Turner, 1999). The plant may not prevent human access but may be of a low nuisance value. | ML | M |
| 2. Reduce tourism? | The adult plant grows to heights of 30-150 cm tall (Davis, 1985; McLaren and Turner, 1999). Therefore infestations of the species may have minor effects to aesthetics and most recreational activities will not be inhibited. The plants toxicity to horses (Bourke et al, 2003) may reduce horse related recreation. | MH | M |
| 3. Injurious to people? | Of the literature consulted (Harden, G. 1993; McLaren, and Turner, 1999; Muyt A., 2001) none mentioned the grass being injurious to humans. Not known to be injurious to people, no prickles, spines or toxins present. | L | MH |
| 4. Damage to cultural sites? | The adult plant grows to heights of 30-150 cm tall (Davis, 1985; McLaren and Turner, 1999) suggesting that height of the plant is likely to have a moderate visual effect in densely infested areas. However no reported effect or damage to cultural sites was found. | ML | M |
| Abiotic | |||
| 5. Impact flow? | Despite the grass being often found near streams and lakes the species is terrestrial (Colgate et al, 1999) and is not known to invade the waterbody or streambed. | L | MH |
| 6. Impact water quality? | Despite the grass being often found near streams and lakes the species is terrestrial (Colgate et al, 1999) and is not known to invade or have any effect on the waterbody or streambed. No measurable effect on water quality. | L | MH |
| 7. Increase soil erosion? | The grass grows in tufts or clumps (Herbarium usu). The adult plants grow to heights of 30-150 cm tall (Davis, 1985; McLaren and Turner, 1999). It is a species that commonly invades already disturbed eroded areas such as disturbed pastures edges of cultivated fields and roadsides (Baldini, 1995; Herbario Virtual; Tutin et al, 1980). Existing with other native and exotic grasses (Walsh and Entwisle 1994). It has the potential to dominate grasslands and pastures as experienced in Mediterranean grasslands (Troumbis et al, 2000). Therefore it is likely that the species can replace and displace exiting species of a similar life form and in the highly disturbed areas it colonises may contribute to soil stability. | L | L |
| 8. Reduce biomass? | Other Phalaris species (such as P. acquatica and P. paradoxa) are known to increase the biomass and fuel load of introduced areas. On the basis that P. coerulescens is closely related with both particularly P. paradoxa (Bourke et al, 2003; Davis, 1985; Richardson et al, 2006) it may have the capacity to displace other species and dominate infested areas, in turn increasing fuel load and biomass. | L | L |
| 9. Change fire regime? | Other Phalaris species are known to have a higher fuel load than the original native grasses (CFA, 2004). Phalaris species have a fuel load of 27.5 tonnes/hectare compared to 2.9 t/h for kangaroo grass (CFA, 2004). On this basis, dense stands of P.coerulescens increase biomass and fuel hazard and are likely to have a minor affect more so on fire intensity than frequency. | ML | M |
| Community Habitat | |||
| 10. Impact on composition (a) high value EVC | EVC= Plains Grassy Woodland (E); CMA=Port Phillip and Westernport; Bioregion= Victorian Volcanic Plains; VH Climate potential. Reported to grow in association with native and exotic grasses (Walsh and Entwisle 1994) some displacement and possible dominance due to it being a persistence and productive grass species (Anderton et al, 1999). It has the potential to dominate grasslands and pastures as experienced in Mediterranean grasslands (Troumbis et al, 2000). | MH | MH |
| (b) medium value EVC | EVC= Grassy Dry Forest (D); CMA= Port Phillip and Westernport; Bioregion= Victorian Volcanic Plain; VH = Climate potential. Reported to grow in association with native and exotic grasses (Walsh and Entwisle 1994) some displacement and possible dominance due to it being a persistence and productive grass species (Anderton et al, 1999). It has the potential to dominate grasslands and pastures as experienced in Mediterranean grasslands (Troumbis et al, 2000). | MH | MH |
| (c) low value EVC | EVC= Wet Forest (LC); CMA= Glenelg Hopkins; Bioregion= Glenelg Plain; MED Climate potential. Reported to grow in association with native and exotic grasses (Walsh and Entwisle 1994) in moist well drained soils (Colegate et al, 1999). Some displacement and possible dominance due to it being a persistence and productive grass species (Anderton et al, 1999). It has the potential to dominate grasslands and pastures as experienced in Mediterranean grasslands (Troumbis et al, 2000). | MH | MH |
| 11. Impact on structure? | Growing up to 150 cm affecting mainly the lower stratum and may have a minimal affect on the lower end of the mid stratum. Reported to be a competitive species therefore associated with other grass species (Under Control, 1999). The species has been found to be a persistence and productive grass species (Anderton et al, 1999). It has the potential to dominate grasslands and pastures as experienced in Mediterranean grasslands (Troumbis et al, 2000), suggesting that it can become a dominant species of the lower strata. | ML | MH |
| 12. Effect on threatened flora? | The impact on threatened flora is indeterminable | MH | L |
| Fauna | |||
| 13. Effect on threatened fauna? | The impact on threatened flora is indeterminable | MH | L |
| 14. Effect on non-threatened fauna? | Strong circumstantial evidence suggests that P.coerulescens is fatal to horses (Bourke et al, 2003). Sheep, goat and cattle seem to be unaffected by the species (Bourke et al, 2003). It can provide an alternate food source for livestock similar to other cultivated Phalaris species (Watson et al, 2000). It contains six alkaloids that may make it unpalatable to natives. No reports of toxicity to natives. The species can have a minor impact on structure and habitat and availability of food resources. | ML | M |
| 15. Benefits fauna? | May provide an alternate, reliable food source for livestock or native animals. Particularly because it can tolerate herb pressure (Colegate et al, 1999). Areas of high infestations in combination with other grass species may provide cover for native animals (e.g. bandicoots). | MH | L |
| 16. Injurious to fauna? | Contains toxic alkaloids poisonous to horses (Bourke et al, 2003). Alkaloids may render it unpalatable to native fauna. Found to have little or no effect on cattle and sheep but found that horses are most susceptible to poisoning once plant has been ingested due to the presence in P.coerulescens of methylated tryptamine and related beta- carboline alkaloids (Bourke et al, 2003). At the moment strong circumstantial evidence suggests that these deaths are associated with P. coerulescens. Toxicity to horses may suggest that it can have the same effect on native fauna however no reported effects on native fauna. | M | L |
| Pest Animal | |||
| 17. Food source to pests? | Can be a food source to goats. In its native range Arevalo et al (2007) studied P.coerulescens dominated pastures under a goat grazing system. | ML | MH |
| 18. Provides harbor? | Growing to heights of up to 150 cm (Davis, 1985; McLaren and Turner, 1999) large, dense infestations may provide temporary harbour to major pest specie such as rabbits. However nothing has been documented in the literature. | M | L |
| Agriculture | |||
| 19. Impact yield? | P. coerulescens in its native range it is a known weed of cultivated fields (Baldini, 1995). The closely related P. paradoxa is a serious weed of cereal crops (Bourke et al, 2003). According to Global Compendium of Weeds it is considered an agricultural weed. In Portugal P. coerulescens amongst other Phalaris species infest a wide variety of crops but principally cereals and uncropped land (Costa, 1981). However in Australia it has not yet been documented as a weed of cultivated fields. Due to the similarities P.coerulescens shares with P. paradoxa (Bourke et al, 2003; Davis, 1985) it is possible that P. coerulescens can potentially invade cultivated fields (pers comm. David McLaren) however the impact is not yet known. | M | L |
| 20. Impact quality? | A known weed of cultivated pastures. However there is no information in the literature that indicates how this species impacts on the quality of produce. | M | L |
| 21. Affect land value? | A known weed of cultivated pastures (Baldini, 1995) however there is no information in the literature describing how this species could affect land values. | M | L |
| 22. Change land use? | Due to toxicity to horses (Bourke et al, 2003) can change grazing system of pastures and subsequently land use. | ML | MH |
| 23. Increase harvest costs? | Currently not a documented weed of cultivated pastures in Australia. There is no evidence that suggests that this species currently requires a control regime outside normal weed management | M | L |
| 24. Disease host/vector? | Benigno and Brook (1972) reported P. coerulescens as a host for the Cocksfoot Mottle Virus. They are viruses transmitted by beetles prevalent in the Gramineae. Its closely related species P. paradoxa is susceptible to a number of viruses including barley stripe mosaic hordeivirus, maize dwarf mosaic potyvirus, and sugarcane mosaic potyvirus (Brunt et al, 1996). Diseases identified and prevalent in Phalaris species, that may affect P. coerulescens, include Ergot and Stem rust, Grass downy mildew fungus, wheat eye spot fungus, powdery mildew and a new disease identified in Victoria, Stagonospora foliicola (Watson and Bourke, 2000). | M | L |
This table can also be viewed as a PDF document (printer friendly).
Impact Assessment Record - Blue canary grass (PDF - 74KB)
Impact Assessment Record - Blue canary grass (DOC - 64KB)
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