Research directed by C. Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service

Information on Risk Assessments
Original risk assessment

Paspalum conjugatum; hilograss

Answer

1.01

Is the species highly domesticated?

y=-3, n=0

n

1.02

Has the species become naturalized where grown?

y=-1, n=-1

y

1.03

Does the species have weedy races?

y=-1, n=-1

n

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

See Append 2

2

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

2

2.03

Broad climate suitability (environmental versatility)

y=1, n=0

y

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

y

2.05

Does the species have a history of repeated introductions outside its natural range? y=-2

?=-1, n=0

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n=0

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n=0

y

3.04

Environmental weed y = 2*multiplier (see Append 2)

n=0

y

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n=0

y

4.01

Produces spines, thorns or burrs

y=1, n=0

n

4.02

Allelopathic

y=1, n=0

n

4.03

Parasitic

y=1, n=0

n

4.04

Unpalatable to grazing animals

y=1, n=-1

n

4.05

Toxic to animals

y=1, n=0

n

4.06

Host for recognized pests and pathogens

y=1, n=0

n

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

n

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

n

4.09

Is a shade tolerant plant at some stage of its life cycle

y=1, n=0

y

4.1

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y=1, n=0

y

4.11

Climbing or smothering growth habit

y=1, n=0

n

4.12

Forms dense thickets

y=1, n=0

y

5.01

Aquatic

y=5, n=0

n

5.02

Grass

y=1, n=0

y

5.03

Nitrogen fixing woody plant

y=1, n=0

n

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

y=1, n=0

n

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

n

6.02

Produces viable seed.

y=1, n=-1

y

6.03

Hybridizes naturally

y=1, n=-1

6.04

Self-compatible or apomictic

y=1, n=-1

6.05

Requires specialist pollinators

y=-1, n=0

n

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

y

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

See left

1

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

y=1, n=-1

y

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

y

7.04

Propagules adapted to wind dispersal

y=1, n=-1

y

7.05

Propagules water dispersed

y=1, n=-1

y

7.06

Propagules bird dispersed

y=1, n=-1

n

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

y

7.08

Propagules survive passage through the gut

y=1, n=-1

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

y

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

y=1, n=-1

y

8.03

Well controlled by herbicides

y=-1, n=1

y

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y=1, n=-1

y

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

y=-1, n=1

n

Total score:

28

Source

Notes

1.01

no evidence

1.02

(1) USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN). [Online Database] National Germplasm Resources Laboratory, Beltsville, Maryland. Available: http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?26835 (07 October 2002)
(2) Mannetje , L. & R.M. Jones (1992) Plant Resourcesof South -East Asia no.4 Forages. Prosea Fundation, Bogor, Indonesia. p.177

(1) Distributional range: probably pantropical, widely naturalized in tropics
(2) Originally from American tropics.

1.03

no evidence

2.01

USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN). [Online Database] National Germplasm Resources Laboratory, Beltsville, Maryland. Available: http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?26835 (07 October 2002)

probably pantropical, widely naturalized in tropics

2.02

2.03

Mannetje , L. & R.M. Jones (1992) Plant Resourcesof South -East Asia no.4 Forages. Prosea Fundation, Bogor, Indonesia. p.177

" P . Conjugatum grows from sea level up to 1700 m altitude."

2.04

USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN). [Online Database] National Germplasm Resources Laboratory, Beltsville, Maryland. Available: http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?26835 (07 October 2002)

probably pantropical, widely naturalized in tropics

2.05

(1) USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN). [Online Database] National Germplasm Resources Laboratory, Beltsville, Maryland. Available: http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?26835 (07 October 2002)
(2) Mannetje , L. & R.M. Jones (1992) Plant Resourcesof South -East Asia no.4 Forages. Prosea Fundation, Bogor, Indonesia. p.177

(1) Distributional range: probably pantropical, widely naturalized in tropics
(2) Originally from American tropics.

3.01

USDA, ARS, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN). [Online Database] National Germplasm Resources Laboratory, Beltsville, Maryland. Available: http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?26835 (07 October 2002)

probably pantropical, widely naturalized in tropics

3.02

Whistler, A.W. (1995) Wayside Plants of The Islands. Isle Botanica, Honolulu. 202pp. p. 176

"It is common to abundant in lawns, roadsides, and other disturbed habitats, particularly in wet places." [left iinentionally blank because answer was YES for agricultural/horticulture weed]

3.03

(1) Silva Freire, A. da; Carvalho Pereira, R.; Kersul do Sacramento, C. (1990) Weed control with mixtures of herbicides in guaraná plantations. Agrotrópica, 1990, Vol.2, No.1, pp.43-55, 33 ref. (2)Hasselwood, E.L. and G.G. Motter. 1983.Handbook of Hawaiian Weeds. University of Hawai‘i Press.

(1) Field trials were conducted at Camamu, Bahia, to evaluate the following herbicide mixtures for the control of weeds (mainly Ageratum conyzoides, Bidens pilosa, Digitaria sanguinalis, Digitaria insularis and Paspalum conjugatum ) in a plantation of 2.5-year-old guaraná (Paullinia cupana var. sorbilis ) shrubs: paraquat + ametryn, asulam, atrazine, metolachlor or simazine at 0.3 + 3.2 kg/ha, diuron + paraquat at 2.4 + 0.3 kg, diuron + glyphosate at 1.6 + 0.8 kg, metribuzin + paraquat at 0.8 + 0.3 kg, MSMA + diuron at 2.4 + 1.6 kg and oxyfluorfen + paraquat at 1.6 + 0.3 kg. The treatments were compared with clearing by machete or hoe. The herbicide mixtures, especially paraquat + ametryn, atrazine, metolachlor, oxyfluorfen or simazine and MSMA + diuron, exhibited good control of most dicotyledonous weeds. Paraquat + oxyfluorfen or asulam and diuron + glyphosate controlled all monocotyledonous weeds, except D. insularis , for 65 d following treatment. No mixture was toxic to guaraná plants. (2)A persistent w

3.04

http://www.botany.hawaii.edu/faculty/cw_smith/pas_con.htm

Neal (1965) noted that "some native forests have become extinct due to this pest."

3.05

Bacon, P., P.J. Terry, N. Waltham, & P.Castro S. (1997) An Electronic Atlas of World Weed and Invasive Plants. Version 1.0, 1997. A database based on the original work "A Geographical Atlas of World Weeds" by Holm et al 1979.

Paspalum spp. were listed as serious, principal to common weeds around the world.

4.01

Whistler, A.W. (1995) Wayside Plants of The Islands. Isle Botanica, Honolulu. 202pp. p. 176

no description of these traits

4.02

no evidence

4.03

no evidence

4.04

AB: The productivity of grazing sheep was assessed under 7-year-old rubber at the Rubber Research Institute of the Malaysia Experimental Station at Sungai Buloh near Kuala Lumpur, between October 1988 and May 1990. The sheep were Dorset x Marlin crossbred lambs and they grazed planted leguminous cover crops and naturally occurring species at a range of stocking rates. In the immature rubber trial, presentation yields of forage declined with time regardless of stocking rate. In the mature rubber trial, presentation yields of forage were low (<1000 kg/ha) due to low light transmission. High stocking rates (>6 sheep/ha) resulted in a decrease in the proportion of palatable species (Pueraria phaseoloides, Paspalum conjugatum, Asystasia gangetica and Mikania micrantha ) and an increase in the proportion of the less palatable species (such as Calopogonium caeruleum and Cyrtococcum oxyphyllum ). Daily liveweight gains ranged from 100 g/lamb per day at 4 sheep/ha to 70 g/lamb per day at 14 sheep/ha in the immature r

4.05

AB: The productivity of grazing sheep was assessed under 7-year-old rubber at the Rubber Research Institute of the Malaysia Experimental Station at Sungai Buloh near Kuala Lumpur, between October 1988 and May 1990. The sheep were Dorset x Marlin crossbred lambs and they grazed planted leguminous cover crops and naturally occurring species at a range of stocking rates. In the immature rubber trial, presentation yields of forage declined with time regardless of stocking rate. In the mature rubber trial, presentation yields of forage were low (<1000 kg/ha) due to low light transmission. High stocking rates (>6 sheep/ha) resulted in a decrease in the proportion of palatable species (Pueraria phaseoloides, Paspalum conjugatum, Asystasia gangetica and Mikania micrantha ) and an increase in the proportion of the less palatable species (such as Calopogonium caeruleum and Cyrtococcum oxyphyllum ). Daily liveweight gains ranged from 100 g/lamb per day at 4 sheep/ha to 70 g/lamb per day at 14 sheep/ha in the immature r

4.06

(1) Liao ChungTa; Shiao ShiuhFeng (20001) Pseudonapomyza asiatica Spencer (Diptera: Agromyzidae), a recently resurgent pest species which damages rice in Taiwan. Plant Protection Bulletin (Taipei), 2001, Vol.43, No.4, pp.235-242, 13 ref.
(2) Abenes, M. L. P.; Khan, Z. R. (1990) Feeding and food assimilation by two species of rice leaffolders (LF) on selected weed plants. International Rice Research Newsletter, 1990, Vol.15, No.3, pp.31-32

(1) AB: P. asiatica was recently rediscovered causing damage to rice in central Taiwan in August 2001. Although this species is conventionally treated as a minor pest of rice, its resurgence and wider distribution require special attention. This study focuses on taxonomic and morphological descriptions of this pest species to assist further diagnostic discrimination; a redescription and illustration in greater detail of the external morphology and male terminalia are given. Moreover, some preliminary data on its ecology (featuring a distribution list and a list of hosts: maize, Cynodon dactylon, Eleusine indica, Eragrostis pilosa, Setaria viridis, Paspalum conjugatum, Leptochloa chinensis and Echinochloa crus-galli ) and preliminary survey data are also provided.
(2) AB: The feeding rate and food assimilation of Cnaphalocrocis medinalis and Marasmia patnalis on 12 weed plants common in rice fields in the Philippines were studied in the greenhouse. Larvae of C. medinalis fed most on Digitaria ciliaris, fol

4.07

no evidence

4.08

http://www.botany.hawaii.edu/faculty/cw_smith/pas_con.htm

no evidence

4.09

(1) Toledo, J. M.; Arias, A.; Schultze-Kraft, R. (1989) Productivity and shade tolerance of Axonopus spp., Paspalum spp. and Stenotaphrum secundatum in the humid tropics. Proceedings of the XVI International Grassland Congress, 4-11 October 1989, Nice, France., 1989, pp.221-222, 2 ref.
(2) Ipor, I. B.; Price, C. E. (1992) Shading effects on growth and partitioning of plant biomass in Paspalum conjugatum Berg. BIOTROPIA, 1992, No.6, pp.55-65, 21 ref.

(1) AB: In the search for grasses for silvopastoral systems, the agressiveness, seasonal DM yield and root length of 13 accessions of Axonopus spp., 23 accessions of Paspalum spp. and 1 accession of Stenotaphrum secundatum were determined in a small-plot experiment in full sunlight and 60% intercepted sunlight. Regardless of season, A. compressus and S. secundatum were shade-preferring species, whereas P. notatum was shade-tolerant. P. pilosum and P. plicatulum showed shade preference during the rainy season and intolerance during the dry, while A. affinis and P. conjugatum were intolerant to shade in the rainy and tolerant in the dry season. Crude protein contents and digestibility in vitro of 10 high-yielding accessions selected for adaptation to shade are presented. These accessions are valuable as potential components of silvopastoral systems.
(2) AB: P. conjugatum plants were grown in a greenhouse with 0, 50 or 75% shading. Leaf and stolon number, DM production and NAR were decreased, and plant heigh

4.1

4.11

Whistler, A.W. (1995) Wayside Plants of The Islands. Isle Botanica, Honolulu. 202pp. p. 176

" a creeping perennial grass"

4.12

http://www.botany.hawaii.edu/faculty/cw_smith/pas_con.htm

It forms a dense ground cover even on acidic, low-nutrient soils [blocks growth of other plants, so acts funtionally as a thicket]

5.01

terrestrial

5.02

Whistler, A.W. (1995) Wayside Plants of The Islands. Isle Botanica, Honolulu. 202pp. p. 176

" a creeping perennial grass"

5.03

grass

5.04

Whistler, A.W. (1995) Wayside Plants of The Islands. Isle Botanica, Honolulu. 202pp. p. 176

" a creeping perennial grass"

6.01

no evidence

6.02

Sauerborn, J. (1985) Studies on the segetal flora of taro (Colocasia esculenta (L.) Schott) and on the germination biology of selected weeds of Western Samoa.[FT: Untersuchungen zur Segetalflora in Taro (Colocasia esculenta (L.) Schott) und zur Keimungsbiologie ausgewählter Unkrautarten auf West-Samoa.] PLITS (Plant Protection Information Tropics/Subtropics), 1985, Vol.3, No.1, 85pp., 77 ref.

AB: Species composition and distribution of the weed flora associated with taro crops in Western Samoa was studied in 1982. Among the 89 species identified belonging to 30 families, Mikania micrantha and Paspalum conjugatum occurred in all areas sampled. The diaspores of these species were capable of germination for 3 months after release from a felled secondary forest, contributing towards a large soil seed bank. Germination studies using the 6 most important weeds of taro (Ageratum conyzoides, Blechum brownei, Crassocephalum crepidioides, M. micrantha, P. conjugatum and P. paniculatum ) indicated that only P. paniculatum possessed any marked dormancy.

6.03

no evidence

6.04

no evidence

6.05

Wagner et al.1990. Manual of flowering plants of Hawaii. Vol 2. University of Hawaii Press. Hawaii. Pg 1481

no evidence [Plants belonging to Poaceae are usually wind pollinated or self pollinating, cleistogamous or apomictic…]

6.06

Whistler, A.W. (1995) Wayside Plants of The Islands. Isle Botanica, Honolulu. 202pp. p. 176

"spreading by long, often reddish-purple stolons."

6.07

Mori, S. A.; Silva, L. A. M.; Lisboa, G.; Pereira, R. C.; Santos, T. S. dos (1980) Studies of weedy plants of southern Bahia 1. Productivity and phenology. [FT: Subsidios para estudos de plantas invasoras no sul do Bahia. 1. Produtividade e fenologia.] Boletim Tecnico, Centro de Pesquisas do Cacau, 1980, No.73, 18 pp., 7 ref.

AB: A 200 X 400 m plot was cleared of all surface vegetation; after 105 days the number, frequency and biomass of the weed species present were determined. On this basis species were ranked in relation to their importance in endangering young cocoa plantations. The most important species were Brachiaria mutica, Ludwigia octovalvis, Cyperus distans, Paspalum conjugatum and L. hyssopifolia. Monocotyledons provided nearly twice as much biomass as dicotyledons, with Cyperaceae and Poaceae having the highest net primary productivity. Few plants had produced seed at 105 days but after 5 months much seed had been shed. Recommendations for weed control in young cocoa plantations are based on these findings.

7.01

Whistler, A.W. (1995) Wayside Plants of The Islands. Isle Botanica, Honolulu. 202pp. p. 176

"It is common to abundant in lawns, roadsides, and other disturbed habitats, particularly in wet places."

7.02

Mannetje , L. & R.M. Jones (1992) Plant Resourcesof South -East Asia no.4 Forages. Prosea Fundation, Bogor, Indonesia. p.178

" P. conjugatum is propagated from prostrate clums, using 2-3 nodes per cutting."

7.03

Mannetje , L. & R.M. Jones (1992) Plant Resourcesof South -East Asia no.4 Forages. Prosea Fundation, Bogor, Indonesia. p.178

"Cut feed can be conserved as hay." [mature spikes may contaminate seeds]

7.04

no direct evidence but the small seeds may be swept by wind and get dispersed.

7.05

Mannetje , L. & R.M. Jones (1992) Plant Resourcesof South -East Asia no.4 Forages. Prosea Fundation, Bogor, Indonesia. p.177

"It is found under plantation crops and also along stream banks, roadsides and in disturbed area on a variety of soils." [no direct evidence but appearence in stream bank may suggest water dispersal]

7.06

no evidence

7.07

Mannetje , L. & R.M. Jones (1992) Plant Resourcesof South -East Asia no.4 Forages. Prosea Fundation, Bogor, Indonesia. p.177

" Wet fruits may become very irritating as they easily stick to one's legs and clothing."

7.08

no evidence

8.01

Calderón, J.; Alán, E.; Barrantes, U. (2000) Structure, size and production of weed seeds in the humid tropic. [FT: Estructura, dimensiones y producción de semilla de malezas del trópico húmedo.] Agronomía Mesoamericana, 2000, Vol.11, No.1, pp.31-39, 15 ref.

AB: "Paspalum conjugatum and P. virgatum produced a larger number of spikelets per floral branch (381 and 1185, respectively) than Ischaemum indicum (81) and Rottboellia cochinchinensis (14). Anemocory, hydrocory and zoocory are mentioned as mechanisms contributing to dispersal of these species." [easily reach 1000 seeds, if there are more than 3 floral branches per square meter]

8.02

Horng, L. C.; Leu, L. S. (1978) The effects of depth and duration of burial on the germination of ten annual weed seeds. Weed Science, 1978, Vol.26, No.1, pp.4-10, 18 ref.

AB: Seeds of Echinochloa crus-galli, Portulaca oleracea, Fimbristylis miliacea, Eleusine indica, Monochoria vaginalis, Polygonum lapathifolium, Cyperus iria, Amaranthus viridis, Cyperus difformis and Paspalum conjugatum were placed in nylon mesh bags on the surface and at 2.5-, 7.5-, 15- and 25-cm depths in the soil in November 1974 for 10, 20, 30, 60, 90, 120, 180, 240, 300 and 365 days. In germination tests, seeds left on the soil surface gave lower % germination than those that were buried. Statistical analysis showed that the total % germination was not significantly different for seeds buried 2.5 cm and deeper for the same time interval. The ten species were classified into 3 groups on the basis of the germination data as follows: in C. difformis, P. oleracea, Eleusine indica and Amaranthus viridis, the % germination remained constant and relatively high; in P. conjugatum % germination remained constant for 240 days and then gradually declined at 300 and 365 days; and in E. crus-galli, M. vaginalis, P.

8.03

(1) Yogaratnam, N. (1971) Weed control under Hevea in Ceylon with herbicide mixtures based on MSMA. Quarterly Journal, Rubber Research Institute of Ceylon, 1971, Vol.48, No.3/4, pp.168-180, 10 ref.
(2) Staalduine, D. van (1974) Weed control in tea plantations in Sumatra, Indonesia. Mededelingen Fakulteit Landbouwwetenschappen Gent, 1974, Vol.39, No.2, pp.465-482, 4 ref.

(1) AB: Seven experiments are reported in which MSMA was used alone or with aminotriazole, 2,4-D amine, sodium chlorate or dalapon to control weeds in mature rubber. Paspalum conjugatum was controlled by 0.825 lb/acre MSMA + 0.188-0.375 lb/acre aminotriazole. A mixed growth of P. conjugatum and Mikania scandens was controlled by 0.825-1.65 lb MSMA + 0.6-0.9 lb 2,4-D amine and this mixture was supplemented with 4-5 lb sodium chlorate or 1-2 lb dalapon when further common weed spp. were present.
(2) AB: "A review is given of the weed problems in tea plantations in Sumatra, together with details of chemical weed control programmes used since 1971. An Ansar mixture (MSMA 48.6% 4 litres + 2,4-D 72% 1.8 litres + sodium chlorate 7.5 kg/ha) controls Borreria spp. and Paspalum conjugatum but is uneconomic against other species. "

8.04

Mannetje , L. & R.M. Jones (1992) Plant Resourcesof South -East Asia no.4 Forages. Prosea Fundation, Bogor, Indonesia. p.178

"Close cutting and heavy grazing are recommended (for culture) since it is tolerant of defoliation"; "It is common to abundant in lawns, roadsides, and other disturbed habitats"

8.05

http://www.botany.hawaii.edu/faculty/cw_smith/pas_con.htm

No serious effort has been made to evaluate this pest of native ecosystems and ranchlands for biological control [It has become a pest here, so enemies not present]