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

Carica papaya (papaya)

Answer

1.01

Is the species highly domesticated?

y=-3, n=0

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

n

4.05

Toxic to animals

y=1, n=0

n

4.06

Host for recognized pests and pathogens

y=1, n=0

y

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

n

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

n

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

n

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

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

y

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

n

7.08

Propagules survive passage through the gut

y=1, n=-1

y

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

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

n

8.05

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

y=-1, n=1

y

Total score:

2

Source

Notes

1.01

[If a specific cultivar were named, then the answer would be yes] In some places in South-East Asia the highly inbred hermaphrodite cultivars of the Solo group from Hawaii have come to the fore, e.g. 'Kapoho', 'Sunrise' and 'Sunset'. Where these introductions are surrounded by local material, much care is needed to maintain the cultivars. Agricultural research in Malaysia has yielded several cultivars, such as 'Subang', 'Sitiawan', 'Batu Arang', 'Kundang' and 'Eksotika' (the latter a Solo cultivar derived from a series of back-crosses involving 'Subang 6' and 'Sunrise'). 'Cavite' is a big-fruited selection in the Philippines. 'Coimbatore-2' and 'Peradeniya', both dioecious cultivars, are suitable for papain production.

http://www.agralin.nl/prosrom/papaya.html

1.02

(1) 'Naturalized in parts of southern United States as the seeds germinate readily.' (2) Sparingly naturalized in Hawaii. (3)Naturalized in many low and medium altitude regions in the Philippine. (4) 'Throughout the tropics they grow almost as weeds ... spreading along raodsides and in waste places.' 'Widely cultivated, escaping, naturalized in Puerto Rico. Also on Mona, Vieques, St. Croix, St. Thomas, St. John and Tortola.' "Widely cultivated and naturalized in southern Florida, Bermuda, throughout the West Indies...'

(1)Horticopia: Trees, Shrubs and groundcover. CD-ROM database. (2)Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. Honolulu. (3)Merrill, e. D. 1923. An enumeration of Philippine flowering plants. Manila Bureau of printing. (4) Little, E. L and Wadsworth. F.H. 1964. Common trees of Peurto Rico and the Virgin Islands. US Dept of Agriculture. Washington D.C.

1.03

No evidence

2.01

It is widespread in the humid tropics and subtropics.

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

2.02

'Though the exact area of origin is unknown, it is believed native to tropical America, perhaps in southern Mexico and neighboring Central America … today it is widely distributed throughout the tropical and warmer subtropical areas of the world…'

http://www.ecoport.org/EP.exe$EntPage?ID=630

2.03

(1)Approximate limits north to south: 32°N to 32°S. Altitude range: 0 - 1500 m (2)It can be grown up to 2100 m near the equator

(1)CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International. (2) http://www.ecoport.org/EP.exe$EntPage?ID=630

2.04

Native to lowland tropical America.

Horticopia: Trees, Shrubs and groundcover. CD-ROM database.

2.05

Has been introduced to several countries.

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

3.01

(1) 'Naturalized in parts of southern United States as the seeds germinate readily.' (2) Sparingly naturalized in Hawaii. (3)Naturalized in many low and medium altitude regions in the Philippine. (4) 'Throughout the tropics they grow almost as weeds ... spreading along raodsides and in waste places.' 'Widely cultivated, escaping, naturalized in Puerto Rico. Also on Mona, Vieques, St. Croix, St. Thomas, St. John and Tortola.' "Widely cultivated and naturalized in southern Florida, Bermuda, throughout the West Indies...'

(1)Horticopia: Trees, Shrubs and groundcover. CD-ROM database. (2)Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. Honolulu. (3)Merrill, e. D. 1923. An enumeration of Philippine flowering plants. Manila Bureau of printing. (4) Little, E. L and Wadsworth. F.H. 1964. Common trees of Peurto Rico and the Virgin Islands. US Dept of Agriculture. Washington D.C.

3.02

No evidence

3.03

No evidence

3.04

No evidence

3.05

No evidence

4.01

No evidence

Horticopia: Trees, Shrubs and groundcover. CD-ROM database.

4.02

Not allelopathic

http://plants.usda.gov/cgi_bin/topics.cgi

4.03

No evidence

4.04

forage to free-grazing small ruminants

Ikhimioya, I.; Olagunju, B. O. 1996. Chemical composition of selected green plants available to small ruminants in the dry season in humid Nigeria. Tropicultura, .14, 115-117.

4.05

Not toxic

http://plants.usda.gov/cgi_bin/topics.cgi

4.06

Insect pests:
Bactrocera dorsalis
Bactrocera papayae
Tetranychus
Toxotrypana curvicauda
Fungus diseases:
Acrosporium caricae
Asperisporium caricae
Cercospora caricae
Glomerella cingulata
Leveillula taurica
Phoma caricae-papayae
Phytophthora palmivora
Pythium
Virus diseases:
papaya mosaic virus
papaya ringspot virus
(2) This site lists 202 fungi to be associated with C. papaya. (3)The oriental fruit fly (Dacus dorsalis) is a major concern of papaya

(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.agralin.nl/prosrom/papaya.html

4.07

No evidence

4.08

Herbaceous, no accumultation of flamable materials

4.09

(1) 'Partial shade to full sun'. 'Plant is full sun for fastest growth …' (2) Shade intolerant

(1) Horticopia: Trees, Shrubs and groundcover. CD-ROM database. (2)http://plants.usda.gov/cgi_bin/topics.cgi

4.1

(1)Grows in clay, sandy, loamy and well drained soils. (2) pH range from 5 to 8 (3)It can tolerate any kind of soil provided it is well-drained and not too dry.

(1)Horticopia: Trees, Shrubs and groundcover. CD-ROM database. (2) http://plants.usda.gov/cgi_bin/topics.cgi (3)http://www.agralin.nl/prosrom/papaya.html

4.11

No evidence - not a vine.

Horticopia: Trees, Shrubs and groundcover. CD-ROM database.

4.12

No evidence.

5.01

Perennial tree or shrub (Caricaceae).

http://plants.usda.gov/cgi_bin/topics.cgi

5.02

5.03

5.04

6.01

No evidence

6.02

Papaya is propagated by seed.

http://www.agralin.nl/prosrom/papaya.html

6.03

Requires artifical conditions (embryo rescue).

Wang DerNan; Hsu ShowFong 1997. Breeding papaya resistant or tolerant to papaya ringspot virus. Special Publication - Taichung District Agricultural Improvement Station, No.38, pp.91-101

6.04

[Depends if plants are hermaphroditic; most plants are dioecious] 'Bags are tied over bisexual blossoms for several days to assure that they are self-pollinated. The progeny of self-pollinated bisexual flowers are 67% bisexual, the rest being female.'

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

6.05

Pollination is basically by wind and aided by small insects like thrips.

http://www.ecoport.org/EP.exe$EntPage?ID=630

6.06

(1) C. papaya is easily grown from fresh seed, normally sown direct in the field. (2) Vegetative spread rate - none.

(1) CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://plants.usda.gov/cgi_bin/topics.cgi

6.07

(1) 'A high initial growth rate leads to early flowering (within 6 months from sowing) -and fruiting (fruit maturing 4-5 months after flowering). ' (2)'Throughout the tropics they grow almost as weeds bearing fruit the first year from seed and spreading ...'

(1)http://www.ecoport.org/EP.exe$EntPage?ID=630 (2)Little, E.L. and Wadsworth, F. H. 1964. Common trees of Puerto Rico and the Virgin Islands. US Dept of Agriculture. Washington D.C.

7.01

Hikers consume fruit and inadvertently discard seeds along trails?

7.02

'Most people would plant papaya for its fruit but it can make a wonderful coarse accent plant in many landscapes.'

Horticopia: Trees, Shrubs and groundcover. CD-ROM database.

7.03

Seeds are relatively large.

http://www.ecoport.org/EP.exe$EntPage?ID=630

7.04

Probably dispersed by birds or some mammal as the fruits are large fleshy.

7.05

Probably dispersed by birds or some mammal as the fruits are large fleshy.

7.06

(1)'This plant is attractive to bees, butterflies and/or birds.' (2)Almost all the bird species roosting on trees were seen pecking on either twigs or fruits (rinds).

(1)http://plantsdatabase.com/go/2084/ (2)Malhi, C. S. 2001. Bird damage to guava (Psidium guava ) and papaya (Carica papaya ). Tigerpaper .28,27-30.

7.07

Probably not as the propagules do not have any means of attachment.

7.08

Assumed since bird dispersed fruit

8.01

Seeds globose, 5 mm in diameter, black or greyish, numerous, attached in 5 rows to interior wall of ovary, enclosed in a gelatinous sarcotesta [high seed production per unit area dure to small plant area and dense clustering of fruits.]

http://www.ecoport.org/EP.exe$EntPage?ID=630

8.02

The seed has a fairly short viability. (2)The Papaya seed is viable for up to three years under cool, dry conditions [lab conditions?]

(1)CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://www.biopark.org/peru/papaya.html

8.03

This paper briefly reviews the literature on weeds and weed control in papaya [pawpaws]. There is limited research on this topic, and nearly all of the research focuses on the use of herbicides. Effective use of paraquat and glyphosate in pawpaws is dependent on avoidance of spray contact to green bark and foliage. Pre-emergence herbicide tolerance is dependent on pawpaw age, size and maturity, and soil type. Only one herbicide, oryzalin, is shown to be tolerated by pawpaws immediately after transplanting. Herbicides with a broader spectrum of weed control, such as diuron and oxyfluorfen, generally injure young pawpaws

Nishimoto, R. K. 1997. Herbicide options for weed control in papaya. Integrated Pest Management Reviews 2:109-111

8.04

(1) 'Ability to regenerate rapidly suited for coppicing'. (2)No reprout ability and no copice potential (opposite from the above reference!!) (3) small plants are easily killed by cutting them off at ground level.

(1)CAB International, 2000. Forestry Compendium Global Module. Wallingford, UK: CAB International. (2)http://plants.usda.gov/cgi_bin/topics.cgi (3)http://www.extento.hawaii.edu/kbase/crop/crops/i_papa.htm

8.05

it is important to use clean land, not replanting papaya in the same field. Damping-off is caused by the soilborne fungi Phytophthora parasitica, P. palmivora and Pythium aphanidermatum.Papaya ringspot is a devastating virus disease that wasdetected in the Philippines in 1982. It had earlier causedconsiderable losses in Hawaii, Florida and Taiwan. Initially,the disease appears as oil streaks on stems and petiolesand as it progresses, mottling of leaves becomes evident.Severely infected plants do not flower and die young. Thevirus is transmitted by aphids.Mosaic is another virus disease transmitted by aphids, and bunchy top is caused by a mycoplasma transmitted by a hopper. Rootknot (Meloidogyne incognita) and reniform (Rotylenchulus reniformis) nematodes infest papaya. Feeding nematodes cause root swellings or root galls, resulting in yellowing and premature abscission of the leaves. Since nematicide treatments are expensive, .It is advisable not to replant papaya on the same land. [incapabale of maintaining