Impact Assessment - Vasey grass (Paspalum urvillei) 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 Vasey 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 - 1 MB)
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Common Name: Vasey grass
Scientific name: Paspalum urvillei

Question	Comments	Rating	Confidence
Recreation
1. Restrict human access?	Perennial grass (Clayton et al. 2007) with leaves to 60 cm and flowers to 180 cm (Walsh & Entwisle 1994); tussocky (Speedy 2004). Unlikely to restrict access.	L	MH
2. Reduce tourism?	Perennial grass (Clayton et al. 2007) with leaves to 60 cm and flowers to 180 cm (Walsh & Entwisle 1994); tussocky (Speedy 2004). That grows amongst other grasses, in scrub (Moore & Edgar 2007) and wetlands (Beadle et al. 2004). Unlikely to be noticed by the average visitor.	L	M
3. Injurious to people?	“No cases of poisoning have been reported” (Speedy 2004). Leaf margins finely scabrid (Moore & Edgar 1970). Pollen is allergenic (Pollen Library.com 2007). Leaves may be able to cut skin, and pollen allergenic at some times of the year (when flowering).	ML	M
4. Damage to cultural sites?	Perennial grass (Clayton et al. 2007) with leaves to 60 cm and flowers to 180 cm (Walsh & Entwisle 1994); tussocky (Speedy 2004). That grows amongst other grasses, in scrub (Moore & Edgar 2007) and wetlands (Beadle et al. 2004). Unlikely to have an aesthetic or structural effect on cultural sites.	L	M
Abiotic
5. Impact flow?	Found on moist and flooded land, rarely on slopes (Rosengurtt 1948), including wetlands (Beadle et al. 2004). However, not noted for ability to grow in flowing water. Unlikely to impact on waterways.	L	M
6. Impact water quality?	Found on moist and flooded land, rarely on slopes (Rosengurtt 1948), including wetlands (Beadle et al. 2004). However, not noted for ability to grow in flowing water. Unlikely to impact on waterways.	L	M
7. Increase soil erosion?	A perennial grass (Clayton et al. 2007) with short rhizomes 1-1.5 cm diameter (Moore & Edgar 2007) that grows in dense stands and displaces native vegetation (PIER 2007). Can invade grasslands, scrub (Moore & Edgar 2007) and wetlands (Beadle et al. 2004) on moist and flooded land (Rosengurtt 1948),. “Too tussocky to control erosion” (Speedy 2004). May reduce the ability of native vegetation to reduce erosion and the ability to invade flooded land suggests that it may increase erosion to some degree.	M	M
8. Reduce biomass?	Grows in dense stands and displaces native vegetation (PIER 2007) and can invade grasslands, scrub (Moore & Edgar 2007) and wetlands (Beadle et al. 2004). Likely to replace biomass.	ML	M
9. Change fire regime?	Unknown.	M	L
Community Habitat
10. Impact on composition (a) high value EVC	EVC=Herb-rich foothill forest (BCS =V); CMA=corangamite; Bioreg=Warrnambool Plain; CLIMATE potential=VH. Grows in dense stands and displaces native vegetation (PIER 2007). Can invade grasslands, scrub (Moore & Edgar 2007) and wetlands (Beadle et al. 2004) but may be shaded out by shrubs and trees (Swarbrick & Skarratt 1994). Capable of having a major effect within the lower strata.	MH	M
(b) medium value EVC	EVC=Lowland Forest (BCS =D); CMA=Corangamite; Bioreg=Otway Plain; CLIMATE potential=VH. Can invade grasslands, scrub (Moore & Edgar 2007) and wetlands (Beadle et al. 2004) but may be shaded out by shrubs and trees (Swarbrick & Skarratt 1994). Capable of having a major effect within the lower strata.	MH	M
(c) low value EVC	EVC=Heathy woodland (BCS =LC); CMA=Corangamite; Bioreg=Otway Plain; CLIMATE potential=VH. Can invade grasslands, scrub (Moore & Edgar 2007) and wetlands (Beadle et al. 2004) but may be shaded out by shrubs and trees (Swarbrick & Skarratt 1994). Capable of having a major effect within the lower strata.	MH	M
11. Impact on structure?	Grows in dense stands and displaces native vegetation (PIER 2007). Can invade grasslands, scrub (Moore & Edgar 2007) and wetlands (Beadle et al. 2004) but may be shaded out by shrubs and trees (Swarbrick & Skarratt 1994). Capable of having a major effect on lower strata, but probably only a minor effect on tree and shrub layers.	MH	M
12. Effect on threatened flora?	Ability to displace native vegetation (PIER 2007) may effect threatened flora. No information found.	MH	L
Fauna
13. Effect on threatened fauna?	Ability to displace native vegetation (PIER 2007) may effect threatened fauna. No information found.	MH	L
14. Effect on non-threatened fauna?	Unpalatable grass that is coarse and hard (Quinn & Clarke 1950) with the ability to invade grassland (Moore & Edgar 2007) and to displace native vegetation (PIER 2007). May reduce the food available to native fauna, but not certain of the degree to which it may do this.	M	M
15. Benefits fauna?	Unpalatable grass that is coarse and hard (Quinn & Clarke 1950) with the ability to invade grassland (Moore & Edgar 2007) and to displace native vegetation (PIER 2007). Unlikely to provide food for indigenous fauna. The ability to form dense stands (PIER 2007) may provide shelter to desirable species.	MH	M
16. Injurious to fauna?	Unpalatable grass that is coarse and hard (Quinn & Clarke 1950) with leaf margins that are finely scabrid (Moore & Edgar 1970). May harm the mouths of indigenous fauna, but no evidence found.	M	L
Pest Animal
17. Food source to pests?	Unpalatable grass that is coarse and hard (Quinn & Clarke 1950). Unlikely to provide a food source to pests.	L	M
18. Provides harbor?	The ability to form dense stands (PIER 2007) may harbour undesirable species as overnight cover.	MH	M
Agriculture
19. Impact yield?	Used as stock feed in Sri Lanka and USA, but “regarded as a weed in subtropical coastal Australia, and stock do not eat it readily” (Speedy 2004). Paspalum was found to compete with sugarcane and reduced the main stem weight to 1/9 and the tillering weight to 1/28 of that measured without competition from this weed. These two measures are “the critical factors in sugarcane yield” (Ishimine 1987). Serious impacts on quantity.	H	MH
20. Impact quality?	No evidence that this weed reduces quality in the literature on its agricultural impacts, dating back to 1950s.	L	MH
21. Affect land value?	No evidence that this weed affects land value in the literature on its agricultural impacts, dating back to 1950s.	L	MH
22. Change land use?	No evidence that this weed changes land use in the literature on its agricultural impacts, dating back to 1950s.	L	MH
23. Increase harvest costs?	There is a substantial literature on control of Paspalum in crops with conventional herbicides (Gonzalez-Ibanez 1987; Losso & Ducroquet 1983; Phillips & Tucker 1974). Unlikely to add to weed control costs.	L	MH
24. Disease host/vector?	Host for bacterial leaf blight of sorghum, brown stripe of rice and red stripe of sugarcane, that can rot stalks and discolour rice grains (Saddler 1994). Host for Xylella fastidiosa of plums (Leite et al 1997). Harbours maize leaf blight - Pseudomonas alboprecipitans (Gitaitis et al. 1978). Food plant for Saccharosydne saccharivora, a serious pest of sugarcane (Ingram 1939). Provides a food source for rice stink bug (Naresh & Smith 1983). Host to several severe pests and diseases.	H	H

Impact Assessment Record - Vasey grass (PDF - 76KB)
Impact Assessment Record - Vasey grass (DOC - 59KB)
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