Pacific Island Ecosystems at Risk (PIER)


Report on invasive plant species in Palau (2002 survey)


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Introduction

Dangerous species not known to be in Palau

Species that are presently the subjects of eradication programs

Species that are invasive or have the potential to become so in Palau

Species that are known or listed as being weedy or invasive elsewhere and are common, weedy or cultivated in Palau

Native species (or Micronesian introductions) exhibiting aggressive behavior.

General observations and recommendations

Species-specific recommendations

Recommendations by State

Appendix 1.  Invasive species of environmental concern

Appendix 2.  Other invasive plant species, mostly ruderal weeds or of agricultural concern

Appendix 3.  Invasive species present in Yap, Guam, Hawaii or Papua New Guinea but not present in Palau

Appendix 4.  Invasive species of environmental concern by location

Appendix 5.  Other invasive species by location

Appendix 6.  Presence of invasive species of environmental concern within Palau

Appendix 7.  Presence of other invasive species within Palau

Appendix 8.  Scientific name synonyms

Appendix 9.  Background material and references


 

Report to the Republic of Palau on Invasive Plant Species of

 Environmental Concern

James C. Space, Barbara M. Waterhouse, Joel E. Miles, Joseph Tiobech and Kashgar Rengulbai

 

 U.S.D.A. Forest Service

Pacific Southwest Research Station

Institute of Pacific Islands Forestry

Honolulu, Hawai‘i, USA

 

1 May 2003

 

 

Report to the Republic of Palau on Invasive Plant Species of Environmental Concern

 

James C. Space, Barbara M. Waterhouse, Joel E. Miles, Joseph Tiobech and Kashgar Rengulbai (1)

The Republic of Palau requested assistance from the US Department of Agriculture, Forest Service, Institute of Pacific Islands Forestry, to conduct a survey of invasive plant species of environmental concern. A less comprehensive survey was conducted as part of a general survey of the major Micronesian islands in 1998(2) .  Similar surveys have been conducted in American Samoa, the Cook Islands, Niue, Samoa and Tonga. . The survey was carried out in December 2002 and January 2003. The entire team surveyed the islands of Koror, Ngerkebesang, Malakal, Babeldaob, Angaur, Peleliu and the Rock Islands while Miles and Tiobech surveyed Sonsorol and Hatohobei States. Tiobech, Rengulbai and Terebkul Tellei surveyed Kayangel. Places of present and former habitation and those used by visitors were surveyed in the Rock Islands (Bablomekang, Betikel, Bkul a Chesemiich, Dwight Beach, Ngchelobel, Ngchus, Ngeanges (Neco), Ngercheu (Carp Resort), Ngerchong, Ngeremdiu, Ngermeyaus, Ngidech and Ulong).

The objectives of the survey were to: (1) identify plant species presently causing problems to natural and semi-natural ecosystems; (2) identify species that, even though they are not presently a major problem, could spread more widely or are known to be problem species elsewhere; (3) confirm the absence of species that are a problem elsewhere and, if introduced to Palau, could be a threat there; and (4) make appropriate recommendations.

During our visit local experts(3) showed us sites of known infestations. We also had available copies of botanical surveys conducted in the past (see Appendix 9, References), particularly those conducted by Fosberg and his colleagues. The survey team inspected Koror State, each State in Babeldaob, and Angaur and Peleliu States by vehicle, focusing on disturbed sites such as roadsides, airstrips, ports and ‘urban’ areas. Limited time prevented thorough inspection of agricultural areas, although where possible these were also included. The Rock Islands and Kayangel, Sonsorol and Hatohobei States were visited by boat and inspected on foot. Rapid visual inspection and recording of known invasive and potentially invasive species along the routes chosen was accompanied by more detailed inspection on foot at a variety of sites. Herbarium specimens (51) of ‘new’, ‘significant’, taxonomically ‘difficult’ or unknown species were collected for later identification or verification. All voucher specimens and duplicates will ultimately be deposited in herbarium collections at the Bishop Museum, University of Guam and Queensland Herbarium.

The intent was only to conduct an overall survey and not an exhaustive survey of the weed flora of the islands. Given the limited duration and nature of the survey it is likely that some potentially invasive species, particularly those occurring in low numbers or cultivated in urban gardens or occurring as agricultural weeds, were overlooked. Periodic surveys and additional surveys of individual species and sensitive areas can and should be conducted as needed. This report summarizes our findings and makes some suggestions and recommendations for further action.

Invasive species occurring in or of threat to Palau have been grouped into five categories:

  1. Species that are invasive elsewhere in similar ecosystems but were not seen on our visit and are not reported in the literature as being present in Palau (249 species).

  2. Species that are presently subjects of eradication programs (4 species).

  3. Species that are invasive or potentially invasive in the Palau (53 species).

  4. Species that are invasive or weedy elsewhere and are common, weedy or cultivated in Palau (95 species).

  5. Native species (or Micronesian introductions) that exhibit aggressive behavior (15 species).

These species are listed in Appendix 1. Additional information about each species is located on an Internet site,  http://www.hear.org/pier, and on the PIER-CD, copies of which have been made available to the Ministry of Resources and Development, the National Biodiversity Coordinator, Palau Community College, the US Natural Resources Conservation Service, The Nature Conservancy and others.

There are a number of other species that are mostly invasive weeds in gardens, fields, and pastures and along roadsides that don’t seem to pose any particular threat to natural or semi-natural ecosystems. Information was collected on these species incidental to the survey for species of environmental concern. A list of these species, compiled from the literature and our observations, is included in Appendix 2.

1. Dangerous species not known to be in Palau

Palau is fortunate that a number of troublesome species have yet to reach the country. These are listed in Appendix 1, Table 1. The following list summarizes the worst of these. These species should receive high priority for exclusion from entry into the country and promptly evaluated for eradication if found to be present.

Several Acacia species are invasive on other Pacific islands, notably A. aulacocarpa (brown salwood, brush ironbark wattle, hickory wattle), A. crassicarpa (northern wattle, Papua New Guinea red wattle) and A. curassavica (redwood). A number of other Acacia species are recorded as invasive throughout the world, so caution should be exercised in planting members of this genus. Acacias are often introduced for forestry, wood supply or watershed protection purposes.

Albizia chinensis (Chinese albizia, silktree) is exceptionally widespread in Samoa. Based on its behavior in Samoa, other Pacific islands should be very cautious about introducing this tree.

Ardisia elliptica (shoebutton ardisia) is a problem species in the Cook Islands, Hawai‘i, French Polynesia, Samoa and Florida (US). It produces prolific fruit and crowds out other species in the forest understory. Birds, which eat the fruit, are a major factor in its spread.

Asystasia gangetica subsp. micrantha (Chinese violet, Philippine violet, coromandel) can grow over and smother other vegetatation and is a serious invader in Malaysia and Indonesia. Small infestations are being eradicated in northern New South Wales, Australia. It spreads by rhizomes and by seed expelled explosively from capsules and would be a serious weed in Palau. The less invasive subsp. gangetica was seen in cultivation in Koror State and on Babeldaob,

Two rubber trees, Castilla elastica (Panama rubber tree) and Funtumia elastica (African rubber tree), are very invasive in Samoa. Birds spread the seeds of Castilla while those of Funtumia are wind-borne "parachute" seeds.

Cardiospermum grandiflorum (balloon vine; heart seed) is very invasive on Rarotonga, Cook Islands, and is reported to be invasive in Australia as well.

Carludovica palmata (Panama hat plant) was found naturalizing in the forest understory on Upolu, Samoa, and thus has the potential to be an invasive plant on other tropical islands.

Cecropia obtusifolia (trumpet tree, guarumo) is an invasive tree species that is a problem in Hawai‘i and the Cook Islands (Rarotonga). Cecropia peltata (trumpet tree), a similar species, is invasive in French Polynesia.

Cestrum diurnum (day cestrum, day jessamine, inkberry) and Cestrum nocturnum (night-flowering cestrum) are problem species on a number of Pacific islands. They are species with bird-spread seeds that are often planted as ornamentals.

Clerodendrum chinense (Honolulu rose) is a shade-tolerant species. It primarily reproduces from root suckers and can form dense thickets, crowding out other species. It is a major pest species in American Samoa and Samoa and is present and invasive on a number of other Pacific islands.

Coccinia grandis  (ivy or scarlet gourd) is a smothering vine that is a serious problem on Saipan. The vines climb over trees and form such dense cover that the forest underneath is completely shaded out and destroyed. It is also invasive in Guam and Hawai‘i and is reportedly present in Fiji and Vanuatu. It is a vegetable commonly used in southeastern Asian cooking and the plant is often introduced for that reason. It readily spreads vegetatively through cuttings and, if fruit is present, by birds and probably pigs.

Cordia alliodora (Ecuador laurel, salmwood) was introduced to Samoa, Tonga and Vanuatu as a forestry tree and has proven quite invasive (Tolfts, 1997).

Cryptostegia grandiflora (rubber vine, India rubber vine) is a climbing vine that has become a serious problem in northeastern Queensland, Australia. It is present in New Caledonia and Fiji. A related species, C. madagascariensis, is present in cultivation in Palau but is less of a threat.

Eugenia uniflora (Surinam cherry) is a small tree sometimes cultivated as an ornamental. It was observed spreading on the islands of Mangaia and Ma‘uke, Cook Islands. Fruit-eating birds probably spread the seeds.

Hiptage benghalensis (hiptage) is a problem species in Hawai‘i and is reported to be a very invasive species on La Réunion and Mauritius. It is also becoming invasive in north Queensland, Australia. The seeds are wind-dispersed and it also can reproduce from cuttings.

Indigofera suffruticosa (indigo) is established on many Pacific islands and is a major weed species in Tonga. It has apparently yet to reach Palau.

Macfadyena unguis-cati (cat’s claw climber) is an aggressive vine that climbs trees and also forms a dense mat on the ground. Control is difficult because it has tuberous roots and reproduces from stem fragments and cuttings. It is a problem species in Hawai‘i and eastern Australia (northern NSW and southeast Queensland). It is cultivated as an ornamental in the US, was observed on Niue and is reported to be moderately invasive in New Caledonia (Meyer, 2000).

Maesopsis eminii (musizi, umbrella tree) is a large African tree that has been introduced into other countries as a timber tree. Fruit-eating birds (and possibly fruit bats) spread its seed and it has become a problem in a number of countries. It was introduced as a timber tree to Fiji, where it is starting to naturalize.

Miconia calvescens (the purple plague, velvetleaf) is undoubtedly the most destructive invasive plant in the Pacific. It has been a disaster to the forest ecosystem of Tahiti in French Polynesia and has subsequently spread to other islands in French Polynesia (Meyer and Florence, 1996). It has also escaped in Hawai‘i and is the subject of an intensive and costly eradication effort there. It recently was discovered in Queensland, Australia, where an eradication project is also under way. This species is an attractive garden plant and might be introduced this way or as tiny seeds on shoes or used equipment.

Other members of the family Melastomataceae (including Arthrostemma ciliatum (everblooming eavender), Heterocentron subtriplinervium (pearl flower), Medinilla magnifica (chandelier tree), Medinilla venosa (holdtight), Melastoma candidum (Asian melastome, Indian rhododendron, Malabar melastome), Melastoma sanguineum (fox-tongued melastoma, red melastome), Memecylon floribundum,, Ossaea marginata, Oxyspora paniculata (bristletips) and Tetrazygia bicolor (Florida clover ash)) that are not native or presently in Palau should also be excluded.

Merremia tuberosa (wood rose), a climbing, smothering vine, is notable for its aggressive behavior on Niue. It is also a problem species in Hawai‘i.

Mucuna pruriens (cow itch, velvet bean) is commonly introduced as a cover crop and for livestock feed. It is a serious problem on Saipan and is considered a weed species in Mexico, Mozambique, Jamaica and Madagascar. While the utilis variety commonly used in agriculture lacks irritating hairs it can apparently revert to type over time.

Odontonema tubaeforme (fire spike, cardinal flower) is a widely cultivated ornamental that is invasive in the understory of moist forests in American Samoa and Samoa. It primarily spreads vegetatively, but over time has managed to cover considerable area.

Passiflora tarminiana [formerly known as P. mollissima in Hawai‘i] (banana poka, banana passionfruit), a smothering vine that is a problem in Hawai‘i, is also absent. It can smother the forest canopy when the sub-canopy vegetation is disturbed. Passiflora rubra (red passionfruit) is very invasive in the Cook Islands. Other Passiflora species not already present (Passiflora alata (wingstem passionflower), Passiflora caerulea (blue passionflower), Passiflora coccinea (scarlet passionflower), Passiflora pulchella (two-lobed passionflower), etc.) should also be excluded.

Phyllostachys spp. and other running bamboos are apparently not present in Palau. Phyllostachys and similar bamboo species spread by means of rhizomes, as opposed to bamboos that grow in clumps, and are extremely difficult to control or remove. Phyllostachys nigra (black bamboo) is a problem species in Hawai‘i while P. bissetii is extremely invasive on the island of Mangaia, Cook Islands.

Pimenta dioica (allspice, pimento) is an invasive forest tree. The seeds are bird-dispersed. It is widespread in Tonga (‘Eua), planted in Hawai‘i (where it is naturalizing) and reported to be planted in French Polynesia and Fiji as well. Pimenta racemosa (bay tree), while less of a problem, readily naturalizes as well; for example, in the Cook Islands.

Piper aduncum (spiked pepper) is invasive in Fiji, Papua New Guinea, the Solomon Islands, Indonesia and Malaysia. Its tiny seeds are dispersed by birds and flying foxes and can be introduced into new areas on machinery, particularly logging equipment. Locally, it spreads by suckers, forming large clumps.

Piper auritum (eared pepper, also called "false kava") has been introduced to some Pacific islands as a fast-growing form of kava, but it is worthless in this regard. It is becoming widespread in Tonga and is presently subject of an eradication campaign on the island of Pohnpei, Federated States of Micronesia. It has also been introduced into Hawai‘i but the local kava growers association is working with the authorities to eradicate it there as well. See also SPC Pest Alert No. 19, False Kava. This species suckers profusely and produces many small seeds that can be spread by birds, rodents and bats and can also be introduced into new areas on machinery. It suckers profusely, forming large clumps. Since little kava is grown in Palau, it is unlikely to be introduced deliberately, but with its very small seeds it might be brought in inadvertently.

All Rubus species (raspberries, blackberries, thimbleberries and brambles) should be excluded. These include Rubus alceifolius (giant bramble), invasive in Australia (Queensland) and La Réunion and native to southeast Asia; Rubus moluccanus (Molucca bramble), a serious pest in the Mascarine Islands and native in New Guinea and Rubus rosifolius (roseleaf raspberry, thimbleberry), very invasive in French Polynesia and Hawai‘i and also native to New Guinea. A number of other Rubus species are invasive. In Hawai‘i, R. argutus (prickly Florida blackberry) and R. niveus (hill or Mysore raspberry) are problems. Introduced Rubus species (in particular, R. niveus) are a major problem in the Galapagos Islands. In general, where Rubus species are not present on tropical islands, they should not be introduced. If already introduced, they should be evaluated as candidates for eradication. The vines form thorny thickets and the fruits are widely dispersed by birds.

Schinus terebinthefolius (Christmas-berry, Brazilian pepper) is a major problem species in Hawai‘i was well as Florida (US) and the Indian Ocean islands of La Réunion and Mauritius. The fruits are very attractive to birds, aiding its spread. It is present, though uncommon, in Guam

Setaria palmifolia (palmgrass, short pitpit) is spectacularly invasive in Samoa, growing in dense, monospecific stands. It is also invasive in Tahiti and Hawai‘i and is on the New Zealand noxious weed list. The seeds are dispersed by wind and possibly by granivorous birds.

Solanum capsicoides (cockroach berry, devil’s apple, soda apple) has been introduced to several South Pacific islands as an ornamental. It is becoming well established in Tonga, particularly on Vava’u. Although small, it is quite spiny and would probably be a problem for agriculture as well as a general nuisance. It produces large amounts of small, tomato-like fruit. Spread may be by birds or pigs or by humans who use the fruit in lei-making.

Solanum mauritianum (bugweed, wild tobacco, tree tobacco) is quite prevalent throughout Tonga and is a noxious weed in South Africa. In Hawai‘i, it is naturalized on slopes and ridges in disturbed wet forest.

Tibouchina herbacea (glorybush, cane ti) is a major problem species in mesic to wet forests in Hawai‘i.

Tribulus cistoides (puncture vine) is a vine with a spiny fruit that is troublesome in coastal habitats in Hawai‘i.

In addition to the grasses mentioned above, a number of other potentially invasive grass species are not yet present in Palau, including Andropogon gayanus, Andropogon glomeratus, Andropogon virginicus, Cenchrus ciliaris, Cortaderia jubata, Cortaderia selloana, Digitaria insularis, Echinochloa polystachya, Hymenachne amplexicaulis, Hyparrhenia rufa, Microlaena stipoides, Paspalum urvillei, Pennisetum clandestinum, Schizachyrium condensatum, Sporobolus elongatus and Tripsacum latifolium. Grasses are easily introduced as contaminants in imported seed, imported sand and gravel or on used machinery, and by their nature tend to be invasive.

The best indicator that a species might be invasive is the fact that it is invasive elsewhere. However, each island ecosystem is unique and invasiveness cannot be predicted with certainty. A good strategy is to be extremely cautious and exclude these and other species known to be invasive or weedy elsewhere (although the best strategy is to exclude all species not shown by risk assessment to be of acceptable risk). Known problem species that have the potential to cause problems in tropical island ecosystems and are not yet present in Palau are listed in Appendix 1, Table 1, and Appendix 2, Table 1. These species should be excluded through plant quarantine and, if establishment is detected, promptly evaluated for eradication. Species that are reported to be present in Guam, Hawai‘i, Yap or Papua New Guinea  but are not present in Palau are listed in Appendix 3. These species would be of high risk of introduction from air and ship traffic between these points and Palau.

2. Species that are presently subjects of eradication programs

Imperata cylindrica (kasoring, blady grass, cogon grass), a very invasive grass and a serious problem for agriculture as well as the environment, is present around the airport on Babeldaob and possibly in Ngardmau State. Eradication is under way but will require long-term follow-up to eliminate this persistent grass. Verification, from flowering specimens, of the identity of the suspect grass in Ngardmau, is a high priority.

Mikania micrantha (teb el yas, mile-a-minute weed), a smothering vine, is widespread throughout the Pacific and is a major pest wherever it occurs. It is spread both by seed (dispersed by wind, as a contaminant on vehicles and machinery or on clothing or in the hair of animals) and vegetatively from broken stem fragments. Each node of the stem can produce roots. It was widespread on Koror and Ngerkebesang and also found on Babeldaob (Airai State). A number of infestations, several quite extensive, were found on Peleliu during this survey and new small infestations were found in Airai and Ngaraard States on Babeldaob and in Koror State as well. An eradication program has made significant progress in eliminating the species but a large amount of work remains, particularly on Peleliu. Continued vigilance will be needed to detect new plants emerging from seed or soil-borne stem fragments and to guard against the possibility of future introductions from infested countries.

Schefflera actinophylla (octopus tree) was formerly present in cultivation. It has bird-dispersed fruits and is invasive in Hawai‘i, French Polynesia and elsewhere in Micronesia. All known examples have been eradicated and no new ones were found during the survey.

Spathodea campanulata (orsachel kui, African tulip tree) has been used to a limited extent in Palau as an ornamental tree. It is a major problem in Fiji, the Hawaiian Islands and some other places. The seeds are wind-dispersed and it also propagates from root suckers and cuttings. Large trees do not stand up well to wind. Further planting of this species is being discouraged and existing trees are gradually being eliminated. No new examples were found during the survey. Continued follow-up and destruction of seedling or sucker regrowth in the vicinity of destroyed trees is important.

3. Species that are invasive or have the potential to become so in Palau

A number of known invasive plants that cause trouble in similar ecosystems have been introduced into Palau (Appendix 1, Table 3). Some of these are already causing problems while others are not. Some are cultivated plants that have not (yet) escaped and their potential for causing damage is so far unknown. However, one of the best predictors of invasiveness is the behavior of the species elsewhere, and these are known troublemakers.

Invasive species already widespread in the Cook Islands

A number of invasive species are already widespread in Palau. Eradication or extensive control is out of the question for these species, but they may still warrant control in sensitive, natural and protected areas such as the national parks and reserves.

Adenanthera pavonina (telengtúngd, telentundalel, coral bean tree), invasive in secondary forests throughout the Pacific, is common in Palau. Although the seeds are eaten and many people consider it native, it was introduced. Coral bean has the ability to overtop many native trees and eventually form monospecific stands. Trees produce large quantities of seed and the tree will grow on a variety of soils. If its behavior on Palau is similar to other Pacific locations, it may eventually become much more widespread.

Allamanda cathartica (allamanda, yellow trumpet vine) is widely planted and naturalized. It is becoming invasive in northern Queensland, Australia, and Papua New Guinea. It has invaded forest and savanna in central Babeldaob.

Arundo donax (giant reed) is found in moist areas and along ditches and riverbanks. "Once established, giant reed can form huge clones, sometimes covering hundreds of acres. It is highly flammable and re-sprouts quickly after burning. Fires help transform communities of native plants into solid stands of giant reed, changing riverbank forests from flood- to fire-defined habitats" (Bell, 1996). It spreads by means of rhizomes and fragments of stems, often carried by water.

Chromolaena odorata (ngesngesil, chromolaena, Siam weed) is a highly invasive pan-tropical weed. This species is a major problem for agriculture as well as the environment and will probably be increasingly prevalent in savanna areas once the Compact Road is completed. It has small, wind-dispersed seeds that can also travel on boots, clothing or used cars or equipment. The biological control agents Pareuchaetes pseudoinsulata (a moth) and Cecidochares [=Procecididochares] connexa (Tephritidae) (a gall fly) have been introduced to Palau (Muniappan and Marutani, 1991). Pareuchaetes pseudoinsulata is not established. Cecidochares connexa is established in Koror State and Babeldaob and appears to be reducing flowering and plant vigor. In addition to the widespread infestations of chromolaena on the main islands, a small infestation was found on Ngidech in the Rock Islands.

Clerodendrum quadriloculare (kleuang, bronze-leaved clerodendrum) is common in cultivation and numerous individuals and small thickets were seen. The species is an attractive ornamental and is commonly planted for that purpose. It is notorious for being a prolific producer of root suckers and, in fact, the plant is easily propagated by means of root cuttings. It is a potential problem because of its ability to invade intact or relatively intact native forests. It has become widespread on Pohnpei, Federated States of Micronesia. In Hawai‘i it is becoming a problem ornamental, producing numerous root suckers that appear some distance from the parent plant. It is fairly widespread on the northern end of Babeldaob (Ngerchelong and Ngardmau States) and dense infestations were observed in Koror as well as Aimeliik and Ngatpang States south of Nekken, where it may have been planted for roadside beautification. Only a few plants were seen on Peleliu and Angaur.

Clidemia hirta (kúi, Koster’s curse) is a serious problem species in Hawai‘i and other locations, including Fiji, the Solomon Islands and Vanuatu. It is a very serious weed of the forest understory on a number of tropical islands. It is shade tolerant and spread by birds and has the potential to invade all the forests of Palau. It was thought to be confined to a single area on Babeldaob but during our survey a single plant was found on the hill above the radio tower on Malakal. That plant was destroyed but there are likely more.

While it is mostly used as a cultivated ornamental, a large number of escapes of Dieffenbachia seguine (spotted dieffenbachia, dumb cane) were noted, probably as a result of discarded plants or cuttings. This species can be invasive and difficult to remove, particularly along streams and other moist areas. It has become a major problem in this regard in American Samoa and Samoa. Where found outside of cultivation this species should be removed, as it reproduces vegetatively and can thrive in the dense shade of an intact native forest canopy, crowding out other species.

Dissotis rotundifolia (dissotis, pink lady) was seen in cultivation and infestations are common, particularly on Babeldaob. The worst example of what the future may hold for this plant is at the old Ngatpang village, where it is forming a dense mat in the forest understory, crowding out or excluding other species. This behavior was also seen in Samoa. It is a problem species as well in Fiji, French Polynesia and Hawai‘i. Since it can reproduce vegetatively, mowing or slashing can spread it more widely or lead to very dense stands.

Falcataria moluccana [=Paraserianthes falcataria] (ukall ra ngebard, Moluccca albizia) is most common in central Babeldaob although it was also seen on Koror. Many of the trees are quite large and appear to have been present for some time. It does not appear to be spreading rapidly and, in fact, native species seem to be seeding in underneath. Some younger trees were noted becoming established in disturbed areas on the edge of the forests. It is much more aggressive and extensively naturalized on Pohnpei (Federated States of Micronesia), Tutuila (American Samoa) and Tahiti (French Polynesia).

Hedychium coronarium (white ginger) was seen on Koror and in cultivation on Ngerkebesang. This and other Hedychium species can be quite invasive in wetlands and in moist areas under the forest understory and are difficult to control. Hedychium species have become extensively established in Hawai‘i, where they are a major problem.

Lantana camara (lantana) is common, both cultivated and naturalized. Wild plants seem to be more common on the northern part of Babeldaob and on Koror and Angaur. A pink form is prevalent in northern Babeldaob and Angaur while a red form is present in Koror and surrounding areas. At least two biological control agents have been introduced, but their present status is unknown. In any case, Lantana doesn’t seem to be a big problem in Palau at the present time.

Leucaena leucocephala (telengtungd, leucaena) is very common, as on most Pacific islands, but it is not as prevalent in Palau as it is in many other locations.

Mimosa diplotricha [=invisa] (mechiuaiuu, giant sensitive plant) is a particularly nasty plant covered with thorns, forming dense tangles that are difficult to walk through. It is present in a number of South Pacific locations (American Samoa, Cook Islands (Aitutaki), Fiji, French Polynesia (Society Islands), New Caledonia, Niue, Papua New Guinea, Solomon Islands and Vanuatu). Based on its behavior on other Pacific islands, it may become much more prevalent in Palau in years to come. Biological control agents were reportedly introduced to Palau, but it is not known if they have become established. If present, they seem to be having little effect. The species is only present to a limited extent on Angaur and is absent from Peleliu.

Mimosa pudica (sensitive plant), a smaller plant than M. diplotricha with only small thorns, is common throughout Palau (except Peleliu) as a component of the weedy vegetation of roadsides and other disturbed areas.

Pennisetum polystachion (desum, mission grass) is commonly found in disturbed areas. It provides fuel for fires and readily spreads after fire, perpetuating a fire cycle. This species has seeds adapted for dispersal by wind and is frequently spread as a contaminant on vehicles and machinery. It is likely that it will become more prevalent in northern Babeldaob when the Compact Road is completed.

Psidium guajava (guabang, kuabang, guava) is common in cultivation and as naturalized plants, but nothing like the dense stands seen in Tonga. This is a major invasive species in Tonga and the Galapagos Islands as well as a problem in French Polynesia (Marquesas Islands), New Caledonia, Hawai‘i and Fiji. Frugivorous birds, as well as rats and feral pigs, disperse the seeds. Perhaps it may, over time, become more widespread.

Solanum torvum (prickly solanum, devil’s fig) is a large spiny species of disturbed areas and fields that can form dense, impenetrable thickets. Its seeds are bird-spread. The principal infestation is at Nekken in Ngatpang and Aimeliik States, Babeldaob. A leaf-eating chrysomelid beetle, Leptinotarsa undecimlineata, is reported to be host-specific and might be a useful control agent. (Waterhouse and Norris, 1987).

Stachytarpheta cayennensis [=urticifolia] (louch beluu, blue rat’s tail, dark blue snakeweed) is very common in Palau as it is throughout the Pacific. While mostly a pest in open areas, it can invade into the forest, particularly when there has been disturbance. Stachytarpheta jamaicensis (louch beluu, blue porterweed, light blue snakeweed) is also common and the two can hybridize. Both species are especially prevalent on Angaur. They will undoubtedly become more common on Babeldaob as disturbance increases.

Tecoma stans (yellow bells, yellow-elder, yellow trumpetbush) is widely cultivated in Palau. It is a serious invader of disturbed areas in Tonga and French Polynesia where it grows in dense stands, commonly with other weedy species. The seeds are wind-dispersed.

Thunbergia grandiflora (bung el etiu, blue trumpet vine, Bengal trumpet) is an aggressive vine that can smother trees. An excellent example of its potential can be seen in Koror. It was also seen in Ngatpang (next to OISCA) and Melekeok States. The plant forms large underground tubers and is difficult to eradicate because of regeneration from the tubers and root and stem fragments. It is a problem species in Australia (a noxious weed in Queensland) and Singapore.

Timonius timon (liberal) is widespread on Angaur and Peleliu. Individual trees and small stands were found on a number of the Rock Islands. It was probably introduced to Angaur and Peleliu during or shortly after World War II and has since spread to the Rock Islands. It is an invader of open, disturbed areas. As time goes by, it seems to be overtopped and replaced by native species. Its presence in the Rock Islands indicates that it is spreading to the north and, unless checked, will probably eventually reach Koror and Babeldaob, where it is also likely to be invasive. Single trees (possibly planted) were observed on Kayangel and Ngerkebesang, so it may already be more widespread than our observations suggest.

Tradescantia spathacea (kobesos, oyster plant, boat plant, boat lily, Moses in a boat) and T. zebrina (wandering jew) are planted as ornamentals in Palau but have escaped in several instances. Several examples of Tradescantia spathacea invading the forest understory were seen on Peleliu. A fairly large patch of naturalized Tradescantia zebrina can be seen in Ngiwal State, Babeldaob, as well as on Angaur. These plants are commonly spread through the dumping of garden cuttings.

Turnera ulmifolia (yellow alder, sage rose) is widely planted as an ornamental. Naturalization was noted at a number of locations. The seed is reported to be carried by ants (Staples et al., 2000) and the species is widely naturalized in the tropics. A related species, Turnera subulata (white alder), was noted in cultivation in Airai State on Babeldaob and on Koror and Ngerkebesang. This species is somewhat weedy in Malaysia.

Sphagneticola [=Wedelia] trilobata (ngesil ra ngebard, Singapore daisy) has become a serious pest on many Pacific islands (Thaman, 1999) as well as in northern Australia. It is both planted and naturalized at a number of locations throughout Palau. It can form dense mats along roadsides and in disturbed areas and is a problem in agriculture. Control by chemical means is difficult and mechanical removal often leaves numerous nodes that freely root and rapidly spread. Mowing or slashing can make the problem worse unless done very frequently and very close to the ground.

Invasive species of limited extent

The following species are limited in extent or have recently become established. Some of them are only in cultivation and could be eradicated at minimal cost. Others are more widespread, but are high priority candidates for eradication because of their invasive potential. Others should be monitored for possible future action, if necessary (see species-specific recommendations).

Acacia farnesiana (Ellington curse, klu, sweet acacia) is present in cultivation in Airai State, Babeldaob. This thorny shrub is a pest in Fiji, French Polynesia, New Caledonia, Solomon Islands and Vanuatu.

Alternanthera brasiliana (Brazilian joyweed, Joseph’s coat) is planted as an ornamental and occasional escapes were seen. It is invasive in Queensland, Australia.

Antigonon leptopus (dilngau, chain of love), a climbing vine often planted as an ornamental, is a widespread pest on Guam. A number of examples, mostly in cultivation, were seen, mostly in Koror. A single example was seen in Ngiwal State, Babeldaob.

A few examples of Asparagus densiflorus (asparagus fern, sprengeri fern) were seen, all in cultivation (often in hanging baskets).  Asparagus densiflorus has recently been found to be rather widespread in Hawai‘i on the island of Kauai. There it is spreading along roadsides and invading secondary forest. It seems to have the ability to withstand herbicide treatments used to control vegetation along roads. The seeds are bird-dispersed, and it can also spread vegetatively through root tubers from discarded plants. On several islands in Tonga, the thorny vines of a closely related species, Asparagus setaceus (not found in Palau), have become established in the forest understory, climbing into the canopy. Both species are commonly sold as ornamentals.

Calliandra calothyrsus (powderpuff, red calliandra) was seen in cultivation at one location in Airai State, Babeldaob, and has the potential to become a weed species.

Calotropis gigantea (calotrope, crown flower, madar) is found in cultivation on Koror, Ngerkebesang, Babeldaob and Peleliu. It is an invasive species in Timor and has naturalized in northwestern Australia.

Cinnamomum verum [=zeylanicum] (ochod ra ngebard, cinnamon) was reported present by Fosberg et al. (1979) but was not seen in our survey or in the botanical survey of the Compact Road (Raulerson et al., 1996). If present, this is a potentially dangerous species. It is actively invading secondary forests in American Samoa and Samoa. It is also present and invasive in the Cook Islands (Rarotonga), Fiji, French Polynesia and Hawai‘i.

Cleome viscosa (tickweed, spider flower), an agricultural weed, was found growing along with Ipomoea hederifolia in a seeded area along the Compact Road, probably as a result of contaminated seed.

Cyperus involucratus [=alternifolius subsp. flabelliformis] (deus , umbrella sedge) was seen only in cultivation at one location in Koror. It is often planted as an ornamental, but can be an invader in wet areas.

Eichhornia crassipes (bung el ralm, water hyacinth) was seen in cultivation on Koror, Ngerkebesang and Babeldaob. Water hyacinth is a well-known problem worldwide in freshwater lakes, ponds, marshes, ditches, canals and slow-moving streams. It reproduces both by seed and vegetatively.

Elaeocarpus angustifolius [=grandis] (blue fig, blue marble tree, quandong), a native of Australia, is a forestry tree that is invading intact and secondary forests in Samoa. It is reported present in Palau (Fosberg et al., 1979), perhaps in old forestry trials on Babeldaob, but was not seen on this survey.

Epipremnum pinnatum cv. 'Aureum' [=Scindapsus aureus] (pothos, money plant) was seen at a number of locations throughout Palau but most commonly in Koror and Airai States. It is mostly in cultivation but this tree-climbing species can invade the forest understory. It is a cultivar of a native plant (Epipremnum pinnatum) but is not native to Palau, apparently originating in the Solomon Islands (Smith, 1979) and widely cultivated. Since it only reproduces vegetatively from cuttings and pieces, the main concern is infestations that become established in the forest. Its main method of spread is through discarded garden cuttings.

Flemingia macrophylla is in cultivation on Koror and in Airai State, Babeldaob. This species is a prolific seed producer and can form dense thickets. It is invasive in Samoa and the Cook Islands. It has the potential to become a serious problem if it escapes cultivation. A related species that is invasive in the South Pacific, Flemingia strobilifera (besungelaiei, luck plant, wild hops), is also present but may be native.

Hevea brasiliensis (Brazilian rubber tree, Para rubber tree) is reported present in Koror (Fosberg et al., 1979) and in Nekken, Babeldaob (per Marcello Brel). This species is reported to be naturalizing in Papua New Guinea and on Christmas Island (Indian Ocean).

Hyptis pectinata (mint weed) was seen in Ngatpang State (and was previously recorded on Angaur (Fosberg et al., 1979) but was not seen there in this survey). Its seeds stick to clothing and to the fur of animals and can also be spread by vehicles and machinery. It is on the Hawaii State noxious weed list, is a noxious weed in Fiji, is very prevalent in Samoa and is becoming so in Tonga. It is a serious weed of disturbed sites and agriculture.

Inga edulis (ice cream bean) is a tree that is becoming invasive in northern Queensland. An example was found growing in front of Palau Community College.

Ipomoea hederifolia (ivy-leaf morning glory, star ipomoea) was found in a seeded roadbank along the Compact road south of Chelab. It may have been a contaminant in the seed applied to the roadside. It is invasive in the Torres Strait islands and Cape York Peninsula, Australia, and is a weed of roadsides and agriculture on several Pacific islands.

Ipomoea quamoclit (asangao, star of Bethlehem, Cupid’s flower, cypress vine) was found growing in a vacant lot at New Ngatpang and as a cultivated plant in Koror. This species is invasive in Fiji and north Queensland, Australia.

Macroptilium lathyroides (cow pea, phasey bean) was found in the same location as Ipomoea hederifolia along the Compact Road and also on Package "B" in Airai State. It may also be a seed contaminant. On a number of islands where this species has been introduced it has become a component of the ruderal vegetation.

Melaleuca quinquenervia (cajeput, paper bark tree) is a native of eastern Australia, New Guinea and New Caledonia. It produces large quantities of wind-dispersed seeds and reproduces profusely after fire or other disturbance. It is a major problem in the State of Florida (US) and is present and naturalizing to some degree on Yap. Occasional trees seen on Babeldaob in a previous survey (Space and Falanruw, 1999) didn’t seem to be spreading.

Melia azedarach (Chinaberry, pride-of-India, Indian lilac) seedlings were seen beneath and around cultivated plants at a residence and a business in Airai. It was also seen in cultivation in Koror. Several seedlings were also noted in Koror that appeared to be self-sown, but the source was not immediately apparent. This species is a prolific producer of seed, which is spread by birds. In Palau, it apparently begins to flower at a very young age. It is invasive in a number of Pacific locations, including the Cook Islands, French Polynesia and Hawai‘i as well as in South Africa. Fosberg et al. (1979) reported this species, so there may be more that we didn’t see (he did not give a specific location, however, so perhaps it was only in cultivation).

Melinis minutiflora (molasses grass) is a species that is particularly dangerous in that it is both invasive and can cause a serious fire hazard. It has modified fire regimes on many islands where it has been introduced (D’Antonio and Vitousek, 1992). It was reported present by Fosberg et al. (1979) but was not seen in our survey. Raulerson et al. (1996) reported it present on Babeldaob but rare.

Panicum maximum (Guinea grass), while not yet widespread in Palau (it is present on Koror and Babeldaob), is another grass that can help perpetuate a fire cycle. It seeds profusely and the seeds are dispersed by wind, birds (e.g. chestnut mannikins), flowing water or as a contaminant. It can survive long periods of drought. Fire will sweep through stands of this grass but it regenerates rapidly from underground rhizomes. It is a problem species in Guam and Hawai‘i and is very prevalent in Samoa and Tonga, forming dense stands in open and disturbed areas.

Pennisetum setaceum (fountain grass) was found in cultivation at two residences in Airai and a resort in Ngerkebesang. It is an attractive ornamental but it can produce large amounts of wind-dispersed seed. While it is most likely to be invasive in dry areas, it could possibly spread in Palau. It is a problem species on dryer sites in Hawai‘i.

Pluchea carolinensis (sour bush) and P. indica (Indian fleabane, Indian pluchea, Indian camphorweed) are present on Peleliu and P. indica is present on Angaur. They are shrubby species with wind-dispersed seed. Pluchea carolinensis is naturalizing extensively on Tongatapu, Tonga, and is reported to be widespread but not presently abundant on Guam. These species may have been accidentally introduced as a result of military activity as both were also introduced to Penrhyn Island (Cook Islands) when an airfield was built there during the Second World War (Bill Sykes, pers. com.). Pluchea indica is found along the seashore and inland on poorer sites both on Peleliu and Angaur while P. carolinensis is located along the airstrip on Peleliu.

Psidium cattleianum (strawberry guava), a small tree that forms dense thickets, is reported to be present on Koror (Fosberg et al., 1979) but was not found during this survey. It is a major problem species in a number of island ecosystems including Hawai‘i and Tahiti in the Pacific and La Réunion and Mauritius in the Indian Ocean. Varieties with red and yellow fruits are known. Birds and pigs (and possibly fruit bats as well) disperse the seeds. This is an extremely dangerous species.

A single tree of Senna siamea (cassod tree, Siamese cassia) was seen in Ngeremlengui State, Babeldaob. It is invasive in Australia (Cape York Peninsula) and reported to be weedy on Tahiti.

Sesbania grandiflora (katurai, hummingbird tree, scarlet wisteria tree) is cultivated as an ornamental in Airai, Melekeok and a few other places. Although not yet a problem in Palau, it was observed to be spreading outside of cultivation in American Samoa and Samoa.

Syngonium angustatum (arrowhead plant, goosefoot plant), a climbing aroid, is widely cultivated in Palau, particularly in Koror and Airai States, and numerous escapes were noted. This species has the ability to spread in the deep shade of intact forests, forming a dense mat on the forest floor as well as climbing trees. It is difficult to eradicate as it is able to reproduce from a single node and stem and root fragments are easily overlooked. It spreads vegetatively from dumped cuttings. It is a problem species in American Samoa, is widespread in Hawai‘i and is quite invasive in Niue.

Syzygium cumini (mesekerrák, Java plum) is reported to be present, perhaps mostly in cultivation, on Koror, Babeldaob and Aulupse‘el (Rock Islands) (Fosberg et al., 1979; Raulerson et al., 1996). This species is invasive in the Cook Islands, Hawai‘i and French Polynesia (Raiatea).

Tephrosia candida (white tephrosia) was found in Aimeliik State on Babeldaob. It has become established as a pest species on a number of Pacific islands. It can form dense thickets, particularly in disturbed areas. Only two small plants were observed during this survey. As it has been recorded as present in Babeldaob for a long time (Fosberg et al., 1979) it may not become a serious pest here.

Vitex parviflora (small-leaved vitex) was reported present in Palau by Fosberg et al. (1979), but was not seen. It may be present in cultivation. It is a native of the Philippines, has bird-dispersed seeds and is invasive in Guam.

4. Species that are known or listed as being weedy or invasive elsewhere and are common, weedy or cultivated in Palau

A large number of other common or weedy introduced species were noted. Many of these species, which might best be termed aggressive weeds, are mostly prevalent along roadsides or on disturbed sites, although some species, particularly alien trees, can gradually spread into forested ecosystems. In the case of vines and plants that form dense ground cover, the regeneration of native species can be inhibited. Some of these species could become a problem in the future, since there is often a long lag time between introduction and when a species begins to cause serious impacts. These species (listed in Appendix 1, Table 4) should be monitored for spread and control measures instigated, if necessary.

Spiny Barleria lupulina (hophead, Philippine violet) was seen in cultivation in Ngchesar State. It is invasive in Timor and some naturalization has been noted in north Queensland and Hawai‘i.

Bryophyllum pinnatum [=Kalanchoë pinnata] (life plant) was seen in cultivation and some seedlings were noted. It reproduces vegetatively and can be invasive on the forest floor.

Duranta erecta (golden dewdrop) is widely planted as an ornamental. While it produces prodigious amounts of fruit, to date naturalized populations have not been seen in Palau or other Pacific islands (although it is reported to be naturalizing in Hawai‘i, Florida and Queensland, Australia).

Episcia cupreata (episcia, flame violet) is widely cultivated but is also growing wild on rock walls and in the forest understory, especially in Koror State.

Hemigraphis alternata (metal leaf, red ivy), introduced as an ornamental, was seen forming dense low stands at several locations, invading under the forest canopy. It is shade tolerant, does well in the forest understory and can exclude other species.

Hyptis capitata (knobweed) is apparently only present on Babeldaob, Koror, Malakal and Ngerkebesang. It is shade tolerant and quite invasive.

Murraya paniculata (orange jessamine, mock orange, satin-wood, Chinese box) was seen cultivated as an ornamental plant. It has bird-dispersed seeds and thus the ability to spread, although it has not been observed to have done so on the Pacific islands where it is present. However, in Asia M. paniculata is the preferred host of the insect pest Diaphorina citri, the citrus psyllid. The psyllid is the vector for the serious citrus disease "huanglongbing".

Passiflora foetida (kudamono, love-in-a-mist) is widespread. It is quite prevalent on most Pacific islands but does not appear to be highly invasive in Palau.

Pithecellobium dulce (kamatsíri, opiuma, Madras thorn) is a thorny tree that is a problem species in Hawai‘i. It is present on most of the major islands of Micronesia, but doesn’t seem to be a major problem. The seeds are bird-dispersed and its sap can cause eye irritation and skin welts. It is relatively resistant to fire and resprouts rapidly by basal or aerial shoots. It was reported present on Koror by Fosberg et al. (1979) but was not seen during our survey.

Occasional patches of Pseuderanthemum carruthersii were seen on Ngerkebesang, Babeldaob, Peleliu and Tobi, but it is more of a problem on Sonsorol, where it is expanding into the forest along roads and paths.

Quisqualis indica (Rangoon creeper) was seen on a fence in Ngerkebesang and at a residence in Airai State.

Ricinus communis (gelug, maskerekur, uluchula skoki, castor bean) is present along roadsides and in disturbed places on Peleliu and Angaur.

Some exotic tree species that have been introduced to Palau include Acacia auriculiformis (earleaf acacia), Acacia confusa (ianángi, yanangi, Formosa koa), Acacia mangium (mangium), Albizia lebbeck (ukall ra ngebard, siris-tree, rain tree), Bauhinia acuminata (dwarf white bauhinia), Bauhinia monandra (orchid tree), Bauhinia purpurea (purple orchid tree), Bauhinia variegata, Ceiba pentandra (kalngebárd, kerrekar ngebard, kapok), Ficus sp., Ficus elastica (komunokí, India rubber tree), Gliricidia sepium (rechesengel, mother of cacao, quickstick), Jacaranda mimosifolia (Jacaranda), Muntingia calabura (budo, Panama cherry), Samanea saman (monkeypod), Syzygium jambos (malabar plum), Tabebuia heterophylla (pink trumpet tree) and Thevetia peruviana (yellow oleander). These species can naturalize and are more or less successful depending on local conditions. In Palau, Acacia auriculiformis is widely planted but in only a few cases were significant numbers of seedlings present, usually where mineral soil was exposed as a result of fire or other disturbance. Acacia mangium is planted in a few locations, but only a few seedlings were noted adjacent to the small forestry planting in Aimeliik State. Muntingia calabura is very common as a volunteer. The rest of the above-mentioned trees seem to reproduce little or not at all in Palau.

In addition to Arundo donax, Imperata cylindrica, Melinis minutiflora, Panicum maximum, Pennisetum polystachion and Pennisetum setaceum, discussed above, a number of other introduced grasses are established, including Bothriochloa bladhii, (desum, blue grass, Australian beardgrass), Cenchrus brownii (burr grass), Cenchrus echinatus (burr grass), Chloris barbata, (swollen fingergrass), Chloris radiata (plush-grass, radiate fingergrass), Cynodon dactylon (Bermuda grass), Digitaria ciliaris (smooth crabgrass), Digitaria violascens (sau, smooth crabgrass, violet crabgrass), Eleusine indica (kelelamalk, keteketarmalk, goosegrass), Panicum repens (torpedo grass), Paspalum conjugatum (udel ra ngebei, T grass), Paspalum paniculatum (Russell river grass, galmarra grass), Pennisetum purpureum (bokso, elephant grass, napier grass, merker grass), Sorghum halepense (Johnson grass), Urochloa [Brachiaria] mutica (para grass) and Urochloa [=Brachiaria] subquadripara (green summer grass, tropical signalgrass). Bamboos (esel) (Bambusa spp.) are also present. Urochloa [=Brachiaria] decumbens has been widely planted for bank stabilization along the route of the Compact Road.

Other weedy species include Calopogonium mucunoides (calopo), Centrosema pubescens (centro), Chamaecrista mimosoides (Japanese tea), Chamaecrista nictitans (partridge pea, Japanese tea senna), Clerodendrum buchananii (butcherechár, red clerodendrum, pagoda-flower), Clerodendrum paniculatum (butcherechár, pagoda flower), Clitoria ternatea (kles, butterfly pea), Crotalaria micans (crotalaria), Cyperus rotundus (nut grass, nutsedge), Desmodium tortuosum (Spanish clover), Kyllinga brevifolia (esechesiding, green kyllinga), Leonurus japonicus (lion’s tail), Macroptilium atropurpureum (siratro), Senna [=Cassia] obtusifolia (coffeeweed, sicklepod) and Senna occidentalis (coffee senna).

Species that are cultivated or of limited extent but have the potential to become more widespread include Asystasia gangetica subsp. gangetica (Chinese violet, Philippine violet, coromandel), Nymphaea spp. (waterlily), Ocimum gratissimum (wild basil), Sanchezia parvibracteata (sanchezia), Schefflera arboricola (dwarf brassia, dwarf schefflera), Senna [=Cassia] alata (candle bush) and Tithonia diversifolia (tree marigold, Mexican sunflower).

Some additional invasive plant species, mostly ruderal weeds or of agricultural concern, seen or reported to be present, are listed in Appendix 2, Table 2.

5. Native species (or Micronesian introductions) exhibiting aggressive behavior

Casuarina equisetifolia (ngas, casuarina, ironwood, Australian pine) is native or more likely an early introduction to the main islands of Palau, but is a recent introduction to Tobi and Helen’s reef. There is a single tree on Tobi that is not yet bearing fruit and there is a naturalized population on Helen’s Reef. These trees may be contributing to beach erosion on several of the Rock Islands due to their shallow root systems.

Chrysopogon aciculatus (iul, Mackie’s pest, lovegrass) is indigenous or an early introduction to the main islands but is a recent introduction to Sonsorol and Tobi. It is not yet present on a number of islands and should not be introduced where it is not present. It is an aggressive, noxious weed that readily withstands trampling, poor soils and mowing. Its sharp seeds can penetrate flesh and work their way in, causing festering sores. Its spiked seeds are carried from place to place in fur, feathers, or clothing.

Other common native grasses (or early introductions) include Ischaemum polystachyum (paddle grass), Ischaemum rugosum (muraina grass), Ischaemum timorense (centipede grass), Saccharum spontaneum (banga ruchel, wild cane, false sugarcane), Sacciolepis indica (glenwood grass), Setaria pumila [=pallide-fusca] (foxtail) and Sporobolus indicus (smutgrass, wiregrass).

A number of thorny thickets of Gmelina elliptica (kalngebard ra belau) were seen on the northern end of Babeldaob and occasional examples were seen in most of the Babeldaob states. It is also present on Malakal. It is particularly prevalent in Ngaraard and Ngerchelong States between Chelab and Ollei village. While native to Palau, this species should not be introduced to islands where it is not already present.

Merremia peltata (kebeas, merremia) is quite invasive along forest edges and wherever there has been disturbance. It is not known whether this species is native or an early introduction to Palau, but it is reported here as a native species. Local people say that there was once less of it, but this may just be because there is now substantially more disturbed area that provides suitable habitat. In any case, whether native or not, it is certainly an aggressive vine, not only in Palau but also on other Pacific islands.

Ipomoea macrantha is another native vine that is widespread on the Rock Islands, Babeldaob and elsewhere.

Operculina turpethum (ongucheta rekung), a native vine common throughout the Pacific, occupies a similar ecological niche as Merremia peltata, and is very prevalent in some locations where the latter species is absent, particularly on Peleliu.

General observations and recommendations

It was not the purpose of the survey to provide an in-depth review of policies and procedures for the management of exotic plant pests. However, the following observations and suggestions are offered. For a more in-depth treatment of the principles of invasive species management the publication "Invasive alien species: a toolkit of best prevention and management practices" is available.

A positive step is the recent appointment of an Invasive Species Officer in the Bureau of Agriculture. This position will serve as a focal point for actions against invasive plant species. Palau is also to be commended for setting up an Invasive Weeds Committee. Close and immediate coordination and cooperation between various government departments and other entities is essential when an invasive species problem is encountered, especially when there is a need to move quickly to eradicate an introduced species. Such a committee can be effective both for long-term strategic actions, such as review and strengthening of relevant laws and regulations, as well as short-term tactical and operational problems, such as action when a new species is found to have been introduced. In addition to a management plan, the committee should draw up a prioritized action plan. This would include critical areas to be protected and species subject to control or eradication as well as which governmental agency is to take the lead in control or eradication measures. Time, money and people are always in limited supply and must be directed to the places where they will do the most good. Economic analysis can be used to assess the costs and benefits of management strategies and prioritize action. Some recommendations are made below as to possible actions against individual plant species, but these should be tested against available resources and other priorities. Strong support is also being provided to the program by the Palau Community College.

Palau has laws and regulations in place that deal with quarantine and new introductions. The first line of defense against invasive species, and the most cost-effective, is to keep them out. Control at ports of entry is essential, and those concerned with the protection of natural ecosystems must work closely with plant protection and quarantine officials to combat known and potential invasive plant species. Plant quarantine officers should receive training to be familiar with both agricultural pests and those that threaten wildland ecosystems. At a minimum, a list of known noxious species to be excluded should be developed and exclusion of these species should be backed by the force of law and regulation. Better yet is to employ the "precautionary principle" (as in Australia and New Zealand and under serious consideration by a number of other countries) to exclude all alien species not shown to be of acceptable risk. Risk assessment and management techniques can be used to assess the likelihood and effects of possible introductions and to develop exclusion and eradication strategies. The Secretariat of the Pacific Community has a Plant Protection Training Officer for Micronesia, Konrad Englberger, who provides assistance to strengthen quarantine operations.

In the case of new introductions, the ability to take prompt action is essential, as expanding infestations soon become uneconomical to control. Provision for emergency response procedures and funding mechanisms to deal with immediate problems should be in place.

Education of the public about the danger of introductions and encouraging the use of native species needs to continue as a long-term campaign. People should be encouraged to take responsible actions such as following quarantine regulations, not dumping garden cuttings in the woods and reporting suspicious plants. There are many instances where an invasive plant started out as a pretty flower planted in a yard or garden. Public service announcements on television or radio can be used and "wanted" posters can be prepared for critical species. Education of schoolchildren is especially important, as this is the most impressionable age. Children can also have a notable effect on the actions of their parents. Prompt follow-up to public reports and inquiries is essential to maintain the credibility of a public education program.

The public also needs to understand that the immediate eradication of a problem species, even if it involves the use of pesticides, may be better than living with a problem species forever. Fortunately, the public has been very supportive of the eradication actions taken so far. A good job appears to have been done in informing and involving the public in proposed control and eradication actions.

Local nurseries, botanical gardens or plant importers can be sources of new introductions. A positive approach is to work together to develop a "white list" of both native and non-native species that the public can be encouraged to plant. Likewise, gardening associations and other village and local groups can perform an important education function for their members in what species to avoid and can assist in reporting and controlling infestations of invasive plants. Needless to say, government agencies should lead the way by promoting the use of non-invasive species, especially those that are native to the country.

Foresters, conservation officers, extension agents and others that spend time in the field should be alert to new species that exhibit invasive behavior. Most pest species are deliberately or inadvertently introduced by people and tend to first become established on farms or in gardens and disturbed areas. Suspicious plant species should be promptly reported. Periodically scheduled surveys can also be conducted for new or expanding infestations. An evaluation should be conducted for any new species that appears to be invasive or is known to be invasive elsewhere. Assistance by an expert who is familiar with the species and methods for its eradication or control should be requested if needed. Prompt action is essential, since once a species becomes widespread, control or eradication can be extremely costly or impossible. Assistance is also available on-line from experts through the Pacific Pestnet list-server, and Palau has already been taking advantage of this service.

Laws and regulations should be reviewed to make sure they are adequate to deal with new introductions. This includes the ability of government to require the control of noxious species on private or customary lands or to take action on private lands if the landowner cannot be located or does not take prompt action. If needed, model laws and regulations can be obtained from states and countries that have implemented them.

Steam cleaning or power washing of all used cars, trucks and equipment coming into Palau must be enforced. This is desirable not only from the standpoint of excluding invasive plants, but also insects and diseases. Especially suspect are roadbuilding machinery, military equipment and off-road vehicles. Quarantine inspectors should be especially vigilant to make sure used cars, trucks and equipment from Guam, Hawai‘i, Southeast Asia, Indonesia, New Guinea, Australia and the Philippines are clean as many dangerous weeds are present in these locations. Likewise, importation of sand, gravel, seed and other easily contaminated material from outside the country should be subject to restriction, inspection and monitoring. Several examples of invasive species moved about with gravel and soil were seen during the survey and possible contamination of the seed used in the stabilization seeding on the Compact Road was noted.

Quarantine inspectors should closely inspect boots, camping equipment and other material for soil and seeds, particularly when they have been used in countries where Miconia calvescens and other small-seeded species are present. It would be desirable to have a question on the customs/quarantine declaration form that asks visitors if they have boots or camping equipment or have been in forests as well as farms (as is done in Australia and New Zealand).

A number of species used in ornamental plantings are, at least to some degree, invasive. While many of these species have desirable ornamental or physical characteristics, planting exotics as opposed to native species is a policy question that needs to be carefully considered. Most species that naturalize to any extent will gradually spread throughout available and suitable habitat, given enough time. Existing exotic species should be monitored for spread and new introductions should be carefully assessed to minimize risk. Areas previously used for agricultural and forestry species trials as well as other areas where exotic species have been planted should be more thoroughly checked for dangerous species than was possible during this survey.

A risk-rating scheme would be useful in evaluating the various known and potential invasive species for their risk of introduction, spread and potential damage. The Institute of Pacific Islands Forestry is testing an adaptation of the Australian risk assessment system to the needs of the Pacific. If this proves to be satisfactory, our hope is to eventually rate all the species listed in the PIER database and provide this information to Pacific island countries. In the meantime, risk assessments can be performed on individual species to help evaluate their potential for invasion and spread. Palau used this procedure to evaluate species for the seeding along the Compact Road.

Palau has set aside areas to be maintained in natural condition as a heritage for future generations, for the protection of native biodiversity and tourism values and as examples of Palau’s original forest cover. Protection of these areas will involve a continuous and long-term effort, even on a small scale, due to the continuing pressure from invading species. Keeping out shade-tolerant species that can invade closed forests is the biggest problem. Intact native forests are the most resistant to invasion and any measures that limit the amount of disturbance will help keep invasive species out.

Palau is encouraged to continue to take advantage of the Federal assistance programs in dealing with invasive plant species. In addition to cost-share funding to provide locally available expertise in forest health protection, experts are also on call from the Forest Service’s Forest Health Protection staff, or they can arrange for expert consultations. Public education on invasive species should be part of the environmental education program. Cost-share funding can also be requested to deal with specific forest health problems, including invasive plants, under the Cooperative Forestry and Hawai‘i Tropical Forestry Recovery Acts. Funding is subject to recommendations resulting from a professional evaluation of the problem and the overall availability of funds. Funding also tends to be prioritized based on an economic evaluation of cost-effectiveness, so rapid eradication of a pest species while it is still confined to a small area will undoubtedly take precedence over the chronic problem of a species that has escaped control.

The purpose of this survey was to give an overall assessment of the situation. In the short time available it was not possible to perform the evaluations that would be needed to justify control or eradication programs for individual species. For many species, therefore, our recommendations are provisional and must be subject to a more complete evaluation as to extent, invasiveness and the possibility of control or eradication. Technical assistance should be requested, if needed, to evaluate individual species.

Species-specific recommendations


Table A. Priority species for exclusion from Palau

Scientific Name

Common Names (abridged)

Family

Invasive in:

Acacia aulacocarpa brown salwood Fabaceae Cook Islands
Acacia crassicarpa redwood Fabaceae Cook Islands
Acacia glauca northern wattle, Papua New Guinea red wattle Fabaceae Cook Islands
Albizia chinensis Chinese albizia, silktree Fabaceae Samoa
Ardisia elliptica shoebutton ardisia Myrsinaceae Cook Islands, French Polynesia, Hawai‘i, Samoa and USA (Florida)
Cardiospermum grandiflorum balloon vine; heart seed Sapindaceae Cook Islands (Rarotonga)
Carludovica palmata Panama hat plant Cyclanthaceae Samoa (Upolu)
Castilla elastica Panama rubber tree Moraceae Samoa
Cecropia obtusifolia trumpet tree, guarumo Cecropiaceae Hawai’i, Cook Islands
Cecropia peltata trumpet tree Cecropiaceae French Polynesia
Cestrum diurnum day cestrum Solanaceae Cook Islands
Cestrum nocturnum night-flowering cestrum Solanaceae Cook Islands, French Polynesia (Tahiti), Samoa, Tonga
Clerodendrum chinense Honolulu rose Lamiaceae Samoa, Tonga and elsewhere
Coccinia grandis ivy gourd, scarlet-fruited gourd Cucurbitaceae Hawai‘i, Saipan
Cordia alliodora Ecuador laurel, salmwood Boraginaceae Samoa, Tonga, Vanuatu
Cryptostegia grandiflora rubber vine, India rubber vine Asclepiadaceae Australia (Queensland)
Eugenia uniflora Surinam cherry Myrtaceae Cook Islands
Funtumia elastica African rubber tree Apocynaceae Samoa
Hiptage benghalensis hiptage Malpighiaceae Hawai’i, La Réunion, Mauritius, Australia (Queensland)
Indigofera suffruticosa indigo Fabaceae Tonga and elsewhere
Macfadyena unguis-cati cat’s-claw climber Bignoniaceae Hawai’i, Niue, New Caledonia
Maesopsis eminii umbrella tree, musizi Rhamnaceae Fiji
Merremia tuberosa wood rose Convolvulaceae Hawai‘i, Niue
Miconia calvescens miconia, velvetleaf, purple plague, bush currant Melastomataceae French Polynesia, Hawai’i
Mucuna pruriens cow itch, velvet bean Fabaceae Saipan
Odontonema tubaeforme fire spike, cardinal flower Acanthaceae American Samoa, Samoa
Passiflora spp. all Passifloraceae not already present Passifloraceae
Passiflora tarminiana banana poka, banana passionfruit, bananadilla Passifloraceae Hawai’i
Phyllostachys spp. running bamboos Poaceae Hawai‘i (P. nigra), Cook Islands (P. bissetii)
Pimenta dioica pimento, allspice Myrtaceae Hawai‘i, Tonga
Pimenta racemosa bay tree Myrtaceae Cook Islands
Piper aduncum spiked pepper Piperaceae Fiji, Papua New Guinea, Solomon Islands, Indonesia, Malaysia
Piper auritum eared pepper, false kava Piperaceae Hawai‘i, Pohnpei, Tonga
Rubus spp. raspberries, blackberries, brambles Rosaceae Hawai‘i, French Polynesia, etc.
Schinus terebinthifolius Christmas-berry, Brazilian pepper Anacardiaceae USA (Hawai‘i, Florida)
Setaria palmifolia palmgrass, short pitpit Poaceae Hawai‘i, French Polynesia (Tahiti), Samoa
Solanum capsicoides cockroach berry, devil’s apple, soda apple Solanaceae Hawai‘i, Samoa, Tonga
Solanum mauritianum bugweed, wild tobacco, tree tobacco Solanaceae Hawai‘i, Tonga
Tibouchina herbacea glorybush, cane ti, tibouchina Melastomataceae Hawai’i
Tribulus cistoides puncture vine Zygophyllaceae Hawai‘i
All grasses all other grass species not already present Poaceae pan-tropical
All melastomes all other non-native melastomes Melastomataceae Hawai’i, etc.

Note: Appendix 1, Table 1 is a complete list of invasive and potentially invasive species of environmental concern not yet present in Palau. Appendix 2, Table 1 contains a list of other invasive species not reported to be present in Palau.



Table B. Cultivated species of possible threat to Palau

Scientific Name

Common Names (abridged)

Family

Present on:

Invasive in:

Acacia farnesiana Ellington curse, klu Fabaceae Babeldaob Fiji, French Polynesia, New Caledonia, Solomon Islands, Vanuatu
Asparagus densiflorus asparagus fern, sprengeri fern, smilax, regal fern Liliaceae Koror, Ngerkebesang Hawai‘i
Calotropis gigantea calotrope, crown flower, madar Ascelepiadaceae Koror, Ngerkebesang, Babeldaob, Peleliu Australia (Northern Territory, northwest Western Australia), Timor
Calliandra calothyrsus powderpuff, red calliandra Fabaceae Babeldaob Indonesia
Cinnamomum verum ochod ra ngebard, cinnamon tree Lauraceae reported present, no location given American Samoa, Cook Islands, Samoa
Cyperus involucratus umbrella sedge Cyperaceae Koror Cook Islands, Tonga
Eichhornia crassipes bung el ralm, water hyacinth Pontederiaceae Koror, Ngerkebesang, Babeldaob pantropical
Elaeocarpus angustifolius blue fig, blue marble tree Elaeocarpaceae reported present, no location given Samoa
Flemingia macrophylla Fabaceae Koror, Babeldaob Cook Islands, Samoa
Hevea brasiliensis Brazilian rubber tree Euphorbiaceae Koror, Babeldaob Christmas Island (Indian Ocean)
Murraya paniculata orange jessamine, satin-wood, Chinese box Rutaceae Koror, Ngerkebesang, Babeldaob French Polynesia, Hawai‘i; host to citrus psyllid
Nymphaea spp. waterlily Nymphaeaceae Koror pantropical
Pennisetum setaceum fountain grass Poaceae Ngerkebesang, Babeldaob USA (California, Hawai‘i), Canary Islands
Quisqualis indica Rangoon creeper Combretaceae Ngerkebesang, Babeldaob Australia (Northern Territory)
Sanchezia parvibracteata sanchezia Acanthaceae Koror, Malakal, Ngerkebesang Hawai‘i
Senna siamea cassod tree, Siamese cassia Fabaceae Babeldaob Australia, French Polynesia (Tahiti)
Sesbania grandiflora katurai, sesbania, scarlet wisteria Fabaceae Koror, Malakal, Babeldaob American Samoa, Samoa
Spathodea campanulata orsachel kui, African tulip tree Bignoniaceae Koror, Ngerkebesang, Babeldaob Fiji, French Polynesia, Hawai’i, Samoa, Vanuatu
Syzygium cumini mesekerrák, Java plum Myrtaceae Koror, Babeldaob, Aulupse‘el Cook Islands, Hawai‘i, French Polynesia (Raiatea)
Syzygium jambos malabar plum, Malay apple Myrtaceae Koror, Babeldaob French Polynesia, Galapagos Islands, Mauritius, La Réunion
Tabebuia heterophylla pink tecoma, pink trumpet tree, white cedar Bignoniaceae Koror, Malakal, Ngerkebesang Hawai‘i
Vitex parviflora small-leaved vitex Verbenaceae reported present in Malakal (Toirechuil) Guam

Note: See Appendix 1, Tables 3 and 4 for a complete list of cultivated plants with invasive potential.



Table C.  Critical species that should be subject to inter-island quarantine

Scientific Name

Common name

Present on:

Acacia farnesiana Ellington curse, klu, sweet acacia Babeldaob
Adenanthera pavonina telengtúngd, telentundalel, coral bean tree Koror, Malakal, Ngerkebesang, Babeldaob
Allamanda cathartica allamanda, yellow trumpet vine Koror, Malakal, Ngerkebesang, Babeldaob
Alternanthera brasiliana Brazilian joyweed, Joseph’s coat Koror, Malakal, Ngercheu (Carp Resort)
Antigonon leptopus dilngau, chain of love Koror, Babeldaob
Arundo donax giant reed Koror, Babeldaob
Asparagus densiflorus asparagus fern, sprengeri fern Koror, Ngerkebesang
Calotropis gigantea calotrope, crown flower, madar Koror, Ngerkebesang, Babeldaob, Peleliu
Calliandra calothyrsus powderpuff, red calliandra Babeldaob
Chromolaena odorata ngesngesil, chromolaena, Siam weed Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu, Ngidech
Cinnamomum verum ochod ra ngebard, cinnamon tree Not known
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Kayangel, Peleliu, Ngercheu (Carp Resort)
Clidemia hirta kúi, Koster’s curse Malakal, Babeldaob
Cyperus involucratus deus, umbrella sedge Koror
Dieffenbachia seguine spotted dieffenbachia, dumb cane Koror, Malakal, Ngerkebesang, Babeldaob, Peleliu
Dissotis rotundifolia dissotis, pink lady Koror, Babeldaob
Eichhornia crassipes bung el ralm, water hyacinth Koror, Ngerkebesang, Babeldaob
Elaeocarpus angustifolius blue fig, blue marble tree Not known
Epipremnum pinnatum cv. ‘Aureum’ pothos, money plant Koror, Malakal, Ngerkebesang, Babeldaob
Falcataria moluccana ukall ra ngebard, Moluccca albizia Koror, Babeldaob
Flemingia macrophylla   Koror, Babeldaob
Hedychium coronarium white ginger Koror, Ngerkebesang
Hevea brasiliensis Brazilian rubber tree, Para rubber tree Koror, Babeldaob
Hyptis capitata knobweed Koror, Malakal, Ngerkebesang, Babeldaob
Hyptis pectinata mint weed Babeldaob, Angaur?
Imperata cylindrica kasoring, blady grass, cogon grass Babeldaob
Ipomoea hederifolia ivy-leaf morning glory, star ipomoea Babeldaob
Ipomoea quamoclit asangao, star of Bethlehem, cypress vine Koror, Babeldaob
Lantana camara lantana Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu, Ngercheu (Carp Resort)
Leucaena leucocephala telengtungd, leucaena Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu, Ngercheu (Carp Resort), Ngerchong, Sonsorol
Macroptilium lathyroides cow pea, phasey bean Babeldaob
Melaleuca quinquenervia cajeput, paper bark tree Babeldaob
Melia azedarach Chinaberry, pride-of-India, Indian lilac Koror, Babeldaob
Melinis minutiflora molasses grass Babeldaob
Merremia peltata kebeas, merremia Koror, Malakal, Ngerkebesang, Babeldaob, Kayangel
Mikania micrantha teb el yas, mile-a-minute weed Koror, Malakal, Ngerkebesang, Babeldaob, Peleliu
Mimosa diplotricha mechiuaiuu, giant sensitive plant Koror, Malakal, Ngerkebesang, Babeldaob, Angaur
Mimosa pudica mechiuaiuu, sensitive plant Koror, Malakal, Ngerkebesang, Babeldaob, Angaur
Panicum maximum Guinea grass Koror, Babeldaob
Pennisetum polystachion desum, mission grass Koror, Malakal, Ngerkebesang, Babeldaob, Peleliu
Pennisetum setaceum fountain grass Ngerkebesang, Babeldaob
Pluchea carolinensis sour bush Peleliu
Psidium cattleianum strawberry guava Koror?
Psidium guajava guabang, kuabang, guava Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu, Bkul a Chesemiich, Ngerchong
Senna siamea cassod tree Siamese cassia Babeldaob
Sesbania grandiflora katurai, hummingbird tree, scarlet wisteria tree Koror, Malakal, Babeldaob
Solanum torvum prickly solanum, devil’s fig Babeldaob
Spagneticola trilobata ngesil ra ngebard, Singapore daisy Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu
Stachytarpheta cayennensis louch beluu, blue rat’s tail, dark blue snakeweed Koror, Malakal, , Babeldaob, Angaur, Kayangel, Peleliu, Ngidech, Urukthapel
Syngonium angustatum arrowhead plant, goosefoot plant Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu
Tephrosia candida white tephrosia Babeldaob
Thunbergia grandiflora bung el etiu, blue trumpet vine, Bengal trumpet Koror, Babeldaob, Kayangel
Timonius timon liberal Ngerkebesang, Angaur, Peleliu, Kayangel, Bkul a Chesemiich, Ngercheu (Carp Resort), Ngerchong, Ngchelobel, Ngeanges
Turnera ulmifolia/subulata yellow alder, sage rose/white alder Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu
Vitex parviflora small-leaved vitex Malakal (Toirechuil)

Note: This table lists only the most serious invasive plants of environmental concern. See Appendix 6 and Appendix 7 for complete lists of species not yet present on each island or island group.



Table D.  Summary of major invasive species present in Palau with recommendations for their management

Scientific Name

Common Names (abridged)

Family

Comments and recommendations

*† Acacia farnesiana Ellington curse, klu, sweet acacia Fabaceae Eradicate.
Adenanthera pavonina telengtúngd, telentundalel, coral bean tree Fabaceae Control as needed in sensitive and natural areas.
Allamanda cathartica allamanda, yellow trumpet vine Apocynaceae Discourage planting; remove when a problem.
Alternanthera brasiliana Brazilian joyweed, Joseph’s coat Amaranthaceae Discontinue planting; be alert to escapes from cultivation; eradicate single plant on Ngercheu Island (Carp Resort) and other isolated plantings.
Antigonon leptopus dilngau, chain of love Polygonaceae Discourage further planting; work to eradicate over time.
Arundo donax giant reed Poaceae Limit burning; control as needed in sensitive and natural areas.
*† Asparagus densiflorus asparagus fern, sprengeri fern Liliaceae Eradicate.
Barleria lupulina hophead, Philippine violet Acanthaceae Eradicate if of limited extent.
Bryophyllum pinnatum life plant Crassulaceae Control outside of cultivation.
Calotropis gigantea calotrope, crown flower, madar Ascelepiadaceae Monitor for spread.
Calliandra calothyrsus powderpuff, red calliandra Fabaceae Eradicate if of limited extent.
Casuarina equisetifolia ngas, casuarina, ironwood, Australian pine Casuarinaceae Eradicate on Tobi and Helen’s Reef; exclude from Sonsorol and other islands of Sonsorol State; consider replacement with more suitable species on Rock Island beaches.
Chromolaena odorata ngesngesil, chromolaena, Siam weed Asteraceae Introduce and maintain biological control agents; eradicate on Ngidech Island and any other isolated areas in the Rock Islands.
Chrysopogon aciculatus iul, Mackie’s pest, lovegrass Poaceae Provide advice on control to Sonsorol and Tobi; promptly eradicate if found on new islands.
Cinnamomum verum ochod ra ngebard, cinnamon tree Lauraceae Eradicate if found and of limited extent.
*† Cleome viscosa tickweed, spider flower Capparaceae Eliminate at the locations where found; survey for it in the road seeding; trace source of contamination.
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Lamiaceae Discourage planting and dumping of cuttings; control outside of cultivation; evaluate for possible eradication on Peleliu and Angaur.
* Clidemia hirta kúi, Koster’s curse Melastomataceae Evaluate extent and the possibility of eradication; request technical assistance for evaluation if needed.
*† Cyperus involucratus deus, umbrella sedge Cyperaceae Eradicate if of limited extent.
Dieffenbachia seguine spotted dieffenbachia, dumb cane Araceae Discourage planting and dumping of cuttings; control outside of cultivation.
Dissotis rotundifolia dissotis, pink lady Melastomataceae Discourage planting and dumping of garden waste; control escaped populations as needed.
Eichhornia crassipes bung el ralm, water hyacinth Pontederiaceae Eradicate if of limited extent.
Elaeocarpus angustifolius blue fig, blue marble tree Elaeocarpaceae Evaluate for invasiveness or eradicate if found and of limited extent.
Epipremnum pinnatum cv. ‘Aureum’ pothos, money plant Araceae Control outside of cultivation, especially when growing in forested area.
Falcataria moluccana ukall ra ngebard, Moluccca albizia Fabaceae Evaluate reproduction and spread (low priority); discourage further planting; control in sensitive and natural areas as needed
Flemingia macrophylla Fabaceae Discontinue planting, control outside of cultivation; eradicate if possible.
Gmelina elliptica kalngebard ra belau Lamiaceae Do not introduce to new islands.
Hedychium coronarium white ginger Zingiberaceae Control outside of cultivation.
Hemigraphis alternata metal leaf, red ivy Acanthaceae Control outside of cultivation.
Hevea brasiliensis Brazilian rubber tree, Para rubber tree Euphorbiaceae Evaluate for invasiveness or eradicate if of limited extent.
Hyptis capitata knobweed Verbenaceae Exclude from islands where it does not occur.
* Hyptis pectinata mint weed Verbenaceae Evaluate extent and eradicate if possible.
* Imperata cylindrica kasoring, blady grass, cogon grass Poaceae Continue eradication program; monitor other suspected sites in Babeldaob to determine presence or absence.
*† Inga edulis ice cream bean Fabaceae Investigate source and extent, eradicate.
*† Ipomoea hederifolia ivy-leaf morning glory, star ipomoea Convolvulaceae Eliminate at the locations where found; survey for it in the road seeding; trace source of contamination.
Ipomoea quamoclit asangao, star of Bethlehem, Cupid’s flower, cypress vine Convolvulaceae Eradicate if of limited extent.
Lantana camara lantana Verbenaceae Check status of previously introduced biocontrol agents, reintroduce or introduce new ones as appropriate; monitor for spread to Rock Islands and destroy any plants found there.
*† Macroptilium lathyroides cow pea, phasey bean Fabaceae Eliminate at the locations where found; survey for it in the road seeding; trace source of contamination.
Melaleuca quinquenervia cajeput, paper bark tree Myrtaceae Monitor for invasiveness.
*† Melia azedarach Chinaberry, pride-of-India, Indian lilac Meliaceae Trace source and distribution, eradicate.
Melinis minutiflora molasses grass Poaceae Monitor for spread, especially if burned; limit burning.
Merremia peltata kebeas, merremia Convolvulaceae Exclude from islands where not present; provide advice to landowners on control.
* Mikania micrantha teb el yas, mile-a-minute weed Asteraceae Continue eradication program and monitor for additional occurrences.
Mimosa diplotricha mechiuaiuu, giant sensitive plant Fabaceae Check status of previously introduced biocontrol agents, reintroduce or introduce new ones as appropriate; exclude from islands where not present.; eradicate on islands with small populations.
Mimosa pudica mechiuaiuu, sensitive plant Fabaceae Exclude from Peleliu and other islands where not present, eradicate promptly if found.
Murraya paniculata orange jessamine, satin-wood, Chinese box Rutaceae Reduce the number of plants to prevent spread of the citrus psyllid if it should be introduced.
Panicum maximum Guinea grass Poaceae Limit burning.
Pennisetum polystachion desum, mission grass Poaceae Work to decrease burning and other disturbance.
*† Pennisetum setaceum fountain grass Poaceae Trace source and distribution, eradicate.
Pithecellobium dulce kamatsíri, opiuma, Madras thorn Fabaceae Locate and monitor for invasiveness.
Pluchea carolinensis sour bush Asteraceae Consider for eradication (low priority).
Pluchea indica Indian fleabane, Indian pluchea, Indian camphorweed Asteraceae Consider for eradication (low priority).
Pseuderanthemum carruthersii Acanthaceae Discourage further planting; control outside of cultivation; eradicate on Sonsorol.
*† Psidium cattleianum strawberry guava Myrtaceae Attempt to locate and eradicate.
Psidium guajava guabang, kuabang, guava Myrtaceae Control as needed in sensitive and natural areas.
Quisqualis indica Rangoon creeper Combretaceae Monitor for invasiveness.
Ricinus communis gelug, maskerekur, uluchula skoki, castor bean Euphorbiaceae Monitor spread; work to reduce existing populations.
*† Schefflera actinophylla octopus tree Araliaceae Confirm eradication.
Senna siamea cassod tree Siamese cassia Fabaceae Eradicate if of limited extent.
Sesbania grandiflora katurai, hummingbird tree, scarlet wisteria tree Fabaceae Discourage further planting; monitor closely for any spread; eradicate if it begins to spread.
Solanum torvum prickly solanum, devil’s fig Solanaceae Evaluate for extent and possible control measures; encourage landowners to control plants on their land.
* Spathodea campanulata orsachel kui, African tulip tree Bignoniaceae Continue eradication program.
Spagneticola trilobata ngesil ra ngebard, Singapore daisy Asteraceae Discourage further planting; local control as needed; exclude from islands where not present.
Stachytarpheta cayennensis louch beluu, blue rat’s tail, dark blue snakeweed Verbenaceae Control as needed in sensitive and natural areas.
Stachytarpheta jamaicensis louch beluu, blue porterweed, light blue snakeweed Verbenaceae Control as needed in sensitive and natural areas.
Syngonium angustatum arrowhead plant, goosefoot plant Araceae Control outside of cultivation, especially when growing in forested area.
Syzygium cumini mesekerrák, Java plum Myrtaceae Locate, monitor for invasiveness.
Tecoma stans yellow bells, yellow-elder, yellow trumpetbush Bignoniaceae Monitor for spread, eradicate on Sonsorol.
Tephrosia candida white tephrosia Fabaceae Monitor for spread.
* Thunbergia grandiflora bung el etiu, blue trumpet vine, Bengal trumpet Acanthaceae Discourage planting; control as needed; eliminate plants outside of cultivation; eradicate in Melekeok and Aimeliik/Ngatpang; evaluate for eventual eradication in Koror.
Timonius timon liberal Rubiaceae Eradicate infestations on the Rock Islands; discourage planting; remove individual specimen(s) planted in Koror and Kayangel.
Tradescantia spathacea kobesos, oyster plant, boat plant, boat lily, Moses in a boat Commelinaceae Discourage further planting and dumping; control outside of cultivation.
Tradescantia zebrina wandering jew Commelinaceae Discourage further planting and dumping; control outside of cultivation.
Turnera subulata white alder Turneraceae Discourage further planting; control outside of cultivation.
Turnera ulmifolia yellow alder, sage rose Turneraceae Discourage further planting; control outside of cultivation.
*† Vitex parviflora small-leaved vitex Verbenaceae Eradicate if found.

*High priority for eradication
Eradication can probably be accomplished at low cost


Recommendations by State

All states

The following recommendations apply to all states:

Scientific Name

Common name

Comments and recommendations

Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Discourage further planting; eradicate outside of urban areas, assist landowners in destroying and disposing of unwanted plants.
Clidemia hirta kúi, Koster’s curse Report occurrences to Bureau of Agriculture for eradication.
Dieffenbachia seguine dieffenbachia Control outside of cultivation.
Dissotis rotundifolia dissotis, pink lady Discontinue planting; discourage dumping of garden waste; control escaped populations as needed.
Epipremnum pinnatum cv. ‘Aureum’ pothos Control outside of cultivation, especially in forested areas.
Imperata cylindrica kasoring, cogon grass Report occurrences to Bureau of Agriculture for eradication.
Merremia peltata kebeas, merremia Work with Koror and Babeldaob States to evaluate control measures.
Mikania micrantha teb el yas, mile-a-minute weed Report occurrences to Bureau of Agriculture for eradication.
Schefflera actinophylla octopus tree Remove trees or report occurrences to Bureau of Agriculture.
Spathodea campanulata orsachel kui, African tulip tree Remove trees or report occurrences to Bureau of Agriculture.
Spagneticola trilobata ngesil ra ngebard, Singapore daisy Discontinue planting; discourage dumping of garden waste; control escaped populations as needed.
Syngonium angustatum arrowhead plant Control outside of cultivation, especially in forested areas.
Tradescantia spathacea kobesos, Moses in a boat Discontinue planting; discourage dumping of garden waste; control escaped populations as needed.
Tradescantia zebrina wandering jew Discontinue planting; discourage dumping of garden waste; control escaped populations as needed.
Turnera ulmifolia/subulata yellow alder, sage rose/white alder Discourage planting of these species, control outside of cultivation.

Discourage dumping of garden waste and cuttings. Many tropical species can reproduce vegetatively and dumping of garden waste can spread them to new areas.

Infrequent mowing or slashing may just spread weed species that reproduce vegetatively, including Dissotis rotundifolia, Tradescantia spathacea, T. zebrina and Sphagneticola [=Wedelia] trilobata.

Limit burning and extinguish wildfires promptly. Fire destroys many native species, which are not well adapted to fire, and favors invasive species, many of which are fire-resistant, fire-promoting or are pioneer species that do well on burned sites. Burning favors invasive species by reducing competition, exposing mineral soil and destroying organic matter, making it difficult for native species to become re-established. Fire can promote the reproduction of fire-adapted species, such as Acacia auriculiformis (earleaf acacia), Arundo donax (giant reed), Chromolaena odorata (ngesngesil, chromolaena, Siam weed), Imperata cylindrica (kasoring, cogon grass), Melinis minutiflora (molasses grass), Panicum maximum (Guinea grass) and Pennisetum polystachion (desum, mission grass). Establishment of these species (and extirpation of native species) can fuel additional fires, leading to a destructive fire cycle.

Disturbance, removal of competition and the exposure of mineral soil favor many invasive species. Undisturbed ecosystems are much more resistant to invasion and limiting roadbuilding, land clearing and timber harvesting to the minimum necessary will help prevent the establishment and spread of invasive plant species.

Following are management recommendations for the most serious invasive plant species in each state. Please see the appropriate appendix tables for a complete list of invasive species in each state (Appendix 4 for species of environmental concern, Appendix 5 for other species).

Kayangel State

Only a small number of invasive species are present in Kayangel. Island residents should institute voluntary quarantine and promptly eradicate undesirable species.

Scientific Name

Common name

Comments and recommendations

Cenchrus echinatus burr grass, sand-bur Provide advice on control.
Thunbergia grandiflora bung el etiu, blue trumpet vine Eradicate.
Timonius timon liberal Eradicate.

Babeldaob States

Construction and completion of the Compact Road will lead to increased threats from invasive plant species on Babeldaob. Improved access will undoubtedly lead to increased disturbance, including roadbuilding, degradation of forest cover and increased risk of wildfire. There will undoubtedly be an increased rate of dispersal of Chromolaena odorata and Pennisetum polystachion northwards into areas that are already more fire-prone. Local control is recommended because both species are fire tolerant and fire-promoting species. Pennisetum polystachion in particular causes hot fires.

Stabilization seeding along the Compact Road should be closely monitored, both during and after road construction. During the survey Cleome viscosa (tickweed, spider flower), Ipomoea hederifolia (ivy-leaf morning glory, star ipomoea) and Macroptilium lathyroides (cow pea, phasey bean) were found growing in the seeded area, probably from contaminated seed. There is also risk of exotic species being brought in on imported sand and gravel. Disturbance from construction will provide the opportunity for existing invasive plants to spread further. The road right-of-way, crew camps and rubbish dumps should be surveyed for invasive species and monitored for a period of time (perhaps as long a five years to allow for latent germination) following completion of the road.

Ngerchelong State

Scientific Name

Common name

Comments and recommendations

Cleome viscosa tickweed, spider flower Investigate for further occurrence; eradicate.
Ipomoea hederifolia ivy-leaf morning glory Investigate for further occurrence; eradicate.
Macroptilium lathyroides cow pea, phasey bean Investigate for further occurrence; eradicate.

Ngaraard State

Scientific Name

Common name

Comments and recommendations

Ipomoea hederifolia ivy-leaf morning glory Investigate for further occurrence; eradicate.
Macroptilium lathyroides phasey bean Investigate for further occurrence; eradicate.
Mikania micrantha teb el yas, mile-a-minute weed Investigate for further occurrence; eradicate.

Ngiwal State

Scientific Name

Common name

Comments and recommendations

Antigonon leptopus dilngau, chain of love Evaluate for further occurrence in cultivation and consider eradication
Tradescantia spathacea kobesos, oyster plant, Moses in a boat Control where invading the forest.
Tradescantia zebrina wandering jew Control where invading the forest.

Melekeok State

Scientific Name

Common name

Comments and recommendations

Sesbania grandiflora sesbania Discontinue planting, monitor existing plants for spread.
Thunbergia grandiflora bung el etiu, blue trumpet vine Eradicate.

Ngchesar State

Scientific Name

Common name

Comments and recommendations

Barleria lupulina hophead Eradicate (landowner said she would destroy – follow up).

Airai State

Scientific Name

Common name

Comments and recommendations

Acacia farnesiana Ellington curse, klu Eradicate.
Calliandra calothyrsus powderpuff, red calliandra Eradicate if of limited extent.
Flemingia macrophylla Discontinue planting, monitor for spread.
Macroptilium lathyroides cow pea, phasey bean Investigate for further occurrence; eradicate.
Melia azedarach Chinaberry Eradicate, follow up on distribution.
Pennisetum setaceum fountain grass Eradicate, follow up on distribution.
Quisqualis indica Rangoon creeper Eradicate single example, others if located.
Quisqualis indica sesbania Discontinue planting, monitor existing plants for spread or eliminate.

Ngardmau State

Scientific Name

Common name

Comments and recommendations

Imperata sp. Follow up report of suspected Imperata cylindrica infestation. Collect flowering sample for verification and commence eradication if it proves to be I. cylindrica.

Ngeremlengui State

Scientific Name

Common name

Comments and recommendations

Senna siamea cassod tree Siamese cassia Eradicate if of limited extent.

Ngatpang State

Scientific Name

Common name

Comments and recommendations

Clidemia hirta Koster’s curse Evaluate for eradication.
Hyptis pectinata mint weed Evaluate distribution, eradicate if possible.
Ipomoea quamoclit asangao, star of Bethlehem Eradicate if of limited extent.
Solanum torvum prickly solanum, devil’s fig Evaluate for eradication.
Thunbergia grandiflora bung el etiu, blue trumpet vine Eradicate

Aimeliik State

Scientific Name

Common name

Comments and recommendations

Centratherum punctatum Eradicate cultivated specimen and any others found.
Chromolaena odorata ngesngesil, chromolaena, Siam weed Check to see if biological control agents are present.
Clidemia hirta Koster’s curse Evaluate for eradication.
Eichhornia crassipes bung el ralm, water hyacinth Evaluate for extent, eradicate if possible.
Imperata cylindrica kasoring, cogon grass Follow up on reported occurrence.
Solanum torvum prickly solanum, devil’s fig Evaluate for control or eradication.
Tephrosia candida white tephrosia Evaluate for invasiveness; control if needed.

Koror State Koror, Malakal and Ngerkebesang

Scientific Name

Common name

Comments and recommendations

Antigonon leptopus chain of love Control outside of cultivation, work to eventually eradicate.
Clidemia hirta Koster’s curse Survey for plants on Malakal, eradicate.
Eichhornia crassipes bung el ralm, water hyacinth Evaluate for extent, eradicate if possible.
Flemingia macrophylla Discontinue planting, monitor for spread, eradicate if naturalizing.
Inga edulis ice cream bean Investigate source; search for additional introductions; eradicate.
Ipomoea quamoclit asangao, star of Bethlehem Eradicate if of limited extent.
Melia azedarach Chinaberry Eradicate.
Pennisetum setaceum fountain grass Eradicate.
Quisqualis indica Rangoon creeper Eradicate single example, others if located.
Quisqualis indica sesbania Discontinue planting, monitor existing plants for spread or eliminate.
Thunbergia grandiflora bung el etiu, blue trumpet vine Control outside of cultivation, evaluate for eradication.
Timonius timon liberal Eradicate planted tree on Ngerkebesang and any others found.

Koror State – Rock Islands

Scientific Name

Common name

Comments and recommendations

Chromolaena odorata ngesngesil, chromolaena, Siam weed Eradicate on Ngidech Island and any other isolated patches.
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Eliminate example at Ngercheu Island (Carp Resort) and wherever else it is found.
Stachytarpheta cayennensis louch beluu, blue rat’s tail Eradicate on Ngidech Island and any other isolated patches.
Timonius timon liberal Eliminate trees on Bkul a Chesemiich, Ngercheu (Carp Resort), Ngchelobel, Ngeanges (Neco) and Ngerchong islands and wherever else it is found.

Peleliu and Angaur

Quite a number of species that are present elsewhere in Palau have not yet made it to these two islands (see Appendix 6, Tables 3 and 5, and Appendix 7, Tables 3 and 5) and there are also several species present on Peleliu and Angaur that are of concern to other islands. It would be desirable to implement some sort of quarantine, even a voluntary one based on public education, to limit the transfer of potentially invasive species to and from these islands.

Peleliu State
 

Scientific Name

Common name

Comments and recommendations

Chromolaena odorata ngesngesil, chromolaena, Siam weed Introduce biocontrol agents.
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Evaluate for possible eradication.
Mikania micrantha teb el yas, mile-a-minute weed Eradicate.
Pluchea carolinensis sour bush Consider eradication if of limited extent.

Angaur State

Scientific Name

Common name

Comments and recommendations

Chromolaena odorata ngesngesil, chromolaena, Siam weed Introduce biocontrol agents.
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Evaluate for possible eradication.
Mimosa diplotricha mechiuaiuu, giant sensitive plant Investigate the feasibility of eradication.

Southwest Islands

Most of the invasive species present in the rest of Palau have yet to reach the Southwest Islands. Internal quarantine should be implemented to prevent the entry of new pests to these islands. Assistance and cooperation should be requested from the national Quarantine Service.

Exotic animal vectors should be controlled, if possible, including dogs, cats and non-native fruit-eating birds and bats.

Sonsorol State – Sonsorol Island

Scientific Name

Common name

Comments and recommendations

Bidens alba beggar’s tick Eradicate (burn on site to prevent moving seeds, monitor for reproduction and new infestations and destroy).
Bryophyllum pinnatum life plant Eradicate.
Canna indica canna lily Discontinue planting; control outside of cultivation; consider eradication.
Celosia argentea esechilamalk, cockscomb Discontinue planting; control outside of cultivation; consider eradication.
Duranta erecta golden dewdrop Discontinue planting; control outside of cultivation; consider eradication.
Leucaena leucocephala telengtungd, leucaena Destroy any new seedlings found.
Muntingia calabura budo, Singapore cherry Discontinue planting; control outside of cultivation; consider eradication.
Pseuderanthemum carruthersii Eradicate (request assistance if needed).
Tecoma stans yellow-elder Eradicate.
Tradescantia spathacea kobesos, oyster plant, Moses in a boat Discontinue planting; control outside of cultivation, consider eradication

Sonsorol State – Pulo Anna Island

Scientific Name

Common name

Comments and recommendations

Tecoma stans yellow-elder Eradicate.

Sonsorol State – Merir Island

Scientific Name

Common name

Comments and recommendations

Muntingia calabura budo, Singapore cherry Consider eradication before it spreads.

Hatohobei State – Tobi Island

Scientific Name

Common name

Comments and recommendations

Acacia auriculiformis Papuan wattle Discontinue planting; control outside of cultivation; consider eradication.
Canna indica canna lily Discontinue planting; control outside of cultivation; consider eradication.
Casuarina equisetifolia ngas, ironwood Eradicate (single tree).
Pseuderanthemum carruthersii Discontinue planting; control outside of cultivation; consider eradication.
Sansevieria trifasciata kitelel, bowstring hemp Discontinue planting; control outside of cultivation; consider eradication.
Tecoma stans yellow-elder Eradicate.

Hatohobei State Helen's Reef

Scientific Name

Common name

Comments and recommendations

Casuarina equisetifolia ngas, ironwood Eradicate.

Appendix 1.  Invasive species of environmental concern

Appendix 2.  Other invasive plant species, mostly ruderal weeds or of agricultural concern

Appendix 3.  Invasive species present in Yap, Guam, Hawaii or Papua New Guinea but not present in Palau

Appendix 4.  Invasive species of environmental concern by location

Appendix 5.  Other invasive species by location

Appendix 6.  Presence of invasive species of environmental concern within Palau

Appendix 7.  Presence of other invasive species within Palau

Appendix 8.  Scientific name synonyms

Appendix 9.  Background material and references


(1)  Former Director, Pacific Southwest Research Station, USDA Forest Service (retired); Botanist, Australian Quarantine and Inspection Service; Associate Professor, Agricultural Science, Palau Community College; Invasives Control Officer, Palau Division of Agriculture and Mineral Resources; and Forester, Palau Division of Agriculture and Mineral Resources, respectively.

(2) Space, James C. and Marjorie Falanruw (1999). Observations on invasive plant species in Micronesia. Report prepared for the meeting of the Pacific Islands Committee, Council of Western State Foresters, Majuro, Republic of the Marshall Islands, February 22-26, 1999.

(3)  We would like to express our sincere appreciation for the hospitality, assistance and support of the State Governors and the members of their staffs who accompanied us in the field, for the enthusiastic participation in the survey of Tarita Holm, National Biodiversity Coordinator, and the boats provided by Edwin Chokai, Senior Quarantine Officer, and the Koror State Rangers for the survey of the Rock Islands.


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This page revised 7 April 2009