Pacific Island Ecosystems at Risk (PIER)


Persea americana


RISK ASSESSMENT RESULTS: Low risk, score: 3 (low risk based on second screen)


Australian/New Zealand Weed Risk Assessment adapted for Hawai‘i.

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

Persea americana (Avocado)

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

n

3.03

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

n=0

n

3.04

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

n=0

n

3.05

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

n=0

n

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

4.05

Toxic to animals

y=1, n=0

y

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

n

5.01

Aquatic

y=5, n=0

n

5.02

Grass

y=1, n=0

n

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

y

6.05

Requires specialist pollinators

y=-1, n=0

n

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

n

6.07

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

See left

4

7.01

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

y=1, n=-1

n

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

n

7.04

Propagules adapted to wind dispersal

y=1, n=-1

n

7.05

Propagules water dispersed

y=1, n=-1

n

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

n

8.02

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

y=1, n=-1

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

Total score:

3

Supporting data:

Source

Notes

1.01

No evidence

1.02

(1)In Hawai‘i, naturalized in disturbed mesic areas, 10-66 m. (2)Florida occasional escape from cultivation (3)Subspontaneous in Mauritius, Seychelles and Rodriguez (4)"cultivated or naturalized"

(1)http://www.hear.org/pier/peame.htm (2)Wunderlin, R. P. 1998, Guide to the vascular plants of Florida. Gainesville, University Press of Florida. (3)Baker. Flora of Mauritius and the SeychellesL. Reeve, and Co., London (4)Adams, C.D. 1972. Flowering plants of Jamaica. University of the West Indies. Mona.

1.03

No evidence

2.01

P. americana originated in Chiapas (Mexico), Honduras and Guatemala, and is now widely distributed throughout the tropics, subtropics or Mediterranean regions

CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International.

2.02

2.03

(1)Altitude range: 0 - 2200 m
(2)USDA hardiness zones 9b - 11.

(1)CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)Southern Trees. CD-Rom database.

2.04

P. americana originated in Chiapas (Mexico), Honduras and Guatemala, and is now widely distributed throughout the tropics, subtropics or Mediterranean regions

CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International.

2.05

Introduced to numerous countries.

CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International.

3.01

(1)In Hawai‘i, naturalized in disturbed mesic areas, 10-66 m. (2)Florida occasional escape from cultivation (3)Subspontaneous in Mauritius, Seychelles and Rodriguez (4)"cultivated or naturalized"

(1)http://www.hear.org/pier/peame.htm (2)Wunderlin, R. P. 1998, Guide to the vascular plants of Florida. Gainesville, University Press of Florida. (3)Baker. Flora of Mauritius and the SeychellesL. Reeve, and Co., London (4)Adams, C.D. 1972. Flowering plants of Jamaica. University of the West Indies. Mona.

3.02

No evidence

3.03

No evidence

3.04

Invasive potential: little, if any, potential at this time

http://hort.ifas.ufl.edu/trees/PERAMEA.pdf

3.05

No evidence

4.01

No evidence

http://www.ecoport.org/EP.exe$EntPage?ID=1659

4.02

No evidence

4.03

No evidence

4.04

No information

4.05

'Ingestion of avocado leaves and/or bark has caused mastitis in cattle, horses, rabbits and goats. Large doses have been fatal to goats. Craigmill et al. at Davis, California, have confirmed deleterious effects on lactating goats which were allowed to graze on leaves of 'Anaheim' avocado an hour each day for 2 days. Milk was curdled and not milkable, the animals ground their teeth, necks were swollen and they coughed, ...'

http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html#Description

4.06

(1)Pests recorded
Fungus diseases:
Cercospora purpurea
Glomerella cingulata
Phytophthora cinnamomi
Virus diseases:
Sunblotch viroid (avocado) The above pathogens were not found to be recognized pests beyond generalist pathogens (e.g. P. cinnamoni)
(2)This website lists 200 fungi to be associated with P. americana. (3)The primary insect pests are: avocado red mite [Oligonychus yothersi (McG)], thrips [red-banded thrips, (Hiliothrips rubrocinctus Giard.), and greenhouse thrips (H. haemorrhoidalis Bouche)], scales [Florida wax scale (Ceroplastes floridensis Comst.), Florida red scale (Chrysomphalus aonidium L.), latania scale (Aspidiotus lataniae Sig.), pyriform scale (Protopulvinaria pyriformis Ckll.)]

(1) CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://nt.ars-grin.gov/fungaldatabases/all/FindRecOneFungusFrame.cfm (3)http://www.hort.purdue.edu/newcrop/Proceedings1990/V1-337.html#Avocado

4.07

'Unripe avocados are said to be toxic. Two resins derived from the skin of the fruit are toxic to guinea pigs by subcutaneous and peritoneal injection. Dopamine has been found in the leaves. The leaf oil contains methyl chavicol. Not all varieties are equally toxic. Rabbits fed on leaves of 'Fuerte' and 'Nabal' died within 24 hours. Those fed on leaves of 'Mexicola' showed no adverse reactions.' - [Did not find any case histories of poisoning in humans].

http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html#Description

4.08

Unlikely -- plants with green twigs/branches, trees require regular moisture

4.09

(1)Full sun and half sun (2)The large seed is an adaptation for supplying young plants with enough food to enable them to survive in the dim forest understorey until they can grow into a gap from a fallen tree.

(1)Horticipia Plant Master. CD-ROM database (2)http://www.museums.org.za/bio/plants/lauraceae/persea_americana.htm

4.1

(1)Grows in clay, sand and loam. pH tolerance acidic and alkaline. (2)The avocado tree is remarkably versatile as to soil adaptability, doing well on such diverse types as red clay, sand, volcanic loam, lateritic soils, or limestone.

(1)Southern Trees. CD-ROM database. (2)http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html#Description

4.11

No evidence - not a vine.

http://www.ecoport.org/EP.exe$EntPage?ID=1659

4.12

No evidence

5.01

P. americana is a small dense evergreen tree, approximately 20 m in height.

CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International.

5.02

P. americana is a small dense evergreen tree, approximately 20 m in height.

5.03

P. americana is a small dense evergreen tree, approximately 20 m in height.

5.04

P. americana is a small dense evergreen tree, approximately 20 m in height.

6.01

Fruit development takes approximately 6-12 months, and will ripen only when picked from the tree

CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International.

6.02

'Fresh seeds germinate in 4 to 6 weeks, and many people in metropolitan areas grow avocado trees as novelty house plants ….'

http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html#Description

6.03

No information on natural hybridization.

6.04

(1)The total data suggested that self-fertilization was responsible for a substantial fraction of fruit set in California groves. (2)New evidence indicates avocado flowers may be both self- and cross-pollinated. Self-pollination occurs during the second flower opening when pollen is transferred to the stigma while cross-pollination may occur when female and male flowers from A and B type varieties open simultaneously.

(1) Kobayashi, M.; Lin JingZhong; Davis, J.; Francis, L.; Clegg, M. T.2000. Quantitative analysis of avocado outcrossing and yield in California using RAPD markers. Scientia Horticulturae 86:135149 (2)http://www.ecoport.org/EP.exe$EntPage?ID=1659

6.05

Self-pollination appears to be primarily caused by wind, whereas cross-pollination may be effected by large flying insects such as bees and wasps.

http://www.ecoport.org/EP.exe$EntPage?ID=1659

6.06

Propagation by seed.

http://www.hear.org/pier/peame.htm

6.07

Seedlings will begin to bear in 4 or 5 years and the avocado tree will continue to bear for 50 years or more.

http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html#Description

7.01

Propagules do not have any means of attachment.

http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html#Description

7.02

Probably yes as this species is popularly grown for its fruit 'avocado'.

CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International.

7.03

Seeds are large (2 cm in diameter).

http://www.museums.org.za/bio/plants/lauraceae/persea_americana.htm

7.04

No information on dispersal. Probably not - the seeds do not have any adaptation for wind dispersal.

7.05

No information on dispersal. Probably not as the habitat is not near rivers or near the ocean.

7.06

(1)does not attract wildlife; [No references to bird dispersal or bird damage. Green fruit with fatty flesh suggests NOT attractive to birds]

http://hort.ifas.ufl.edu/trees/PERAMEA.pdf

7.07

(2) 'Spread by pigs and cattle in the Galapagos Islands.' But no information regarding how the seeds are dispersed by these animals. (2)fruits are commonly attacked by squirrels, rats and mice [but no evidence of dispersal by these small animals; in the neotropics, the fatty fruits are eaten by jaguars]

(1)http://www.hear.org/pier/peame.htm (2)http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html

7.08

The large seed are probably NOT swallowed

8.01

(1)It has one large seed. (2)Wild fruit are 4-5 cm in diameter with a 2 cm diameter seed

(1)http://www.ecoport.org/EP.exe$EntPage?ID=1659 (2)http://www.museums.org.za/bio/plants/lauraceae/persea_americana.htm

8.02

(1)Normally, avocado seeds lose viability within a month. In Australia, seeds planted in early fall germinate in 4 to 6 weeks; if planted later, they may remain dormant all winter and germinate in early spring. (2) Wild fruit are 4-5 cm in diameter with a 2 cm diameter seed. The large seed is an adaptation for supplying young plants with enough food to enable them to survive in the dim forest understorey until they can grow into a gap from a fallen tree. [might form a seedling bank in certain circumstances, but don't know if seedlings survive > 1 year]

(1)http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html#Description (2)http://www.museums.org.za/bio/plants/lauraceae/persea_americana.htm

8.03

(1)Bromacil was toxic to avocado (2)If the surplus trees are not bulldozed but just cut down leaving a stump, application of herbicide may be needed to prevent regrowth. Ammonium sulfamate has been proven effective.

(1)Harkness, R. W.; Byrd, C. D.1972. Weed control in lime, avocado and mango groves. Proceedings of the Florida State Horticultural Society,.84:285-290 (2)http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html

8.04

If the surplus trees are not bulldozed but just cut down leaving a stump, application of herbicide may be needed to prevent regrowth.

http://www.hort.purdue.edu/newcrop/morton/avocado_ars.html

8.05

Root rots on poorly-drained soils can be troublesome. [may prevent naturalization in mesic and wet forests]

http://hort.ifas.ufl.edu/trees/PERAMEA.pdf


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This page updated 6 March 2005