Pacific Island Ecosystems at Risk (PIER)

Report on invasive species in Chuuk, Federated States of Micronesia

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Dangerous species not known to be in Chuuk

Species that are invasive elsewhere and are likewise invasive or have the potential to become so in Chuuk

Species that are mentioned or listed as weedy or invasive elsewhere and are cultivated, common or weedy in Chuuk

Native species (or early introductions) exhibiting aggressive behavior

Strategies for dealing with invasive species


Appendix 1.  References

Appendix 2. Species by category

Appendix 3.  Other invasive plant species, mostly of agricultural concern, reported to be present in Chuuk

Appendix 4. Invasive species present in Guam or Pohnpei but not present in Chuuk

Appendix 5. Scientific name synonyms


Invasive plant species in Chuuk, Federated States of Micronesia


James C Space, Barbara Waterhouse, Julie S. Denslow, Duane Nelson and

Thomas R. Mazawa


U.S.D.A. Forest Service

Pacific Southwest Research Station

Institute of Pacific Islands Forestry

Honolulu, Hawai‘i, USA


21 December 2000




17 April 2000

Invasive plant species in Chuuk, Federated States of Micronesia

James C Space, Barbara Waterhouse, Julie S. Denslow, Duane Nelson and Thomas R. Mazawa(1)

This is a continuation of the survey of islands in Micronesia and American Samoa for invasive plant species requested by the Pacific Islands Committee, Council of Western State Foresters. A survey of other Micronesian islands was conducted in 1998 and was discussed in a previous report(2). This report is based on a survey of several islands of Chuuk, Federated States of Micronesia, from 30 March to 4 April 2000. The objectives, as with the previous survey, were three-fold: (1) To identify plant species on the islands that are presently causing problems to natural and semi-natural ecosystems; (2) to identify species that, even though they are not presently a major problem, could spread more widely or spread to other islands where they are not present, potentially causing problems; and (3) to confirm the absence of species that are a problem elsewhere and, if introduced to Chuuk, could be a threat there. While Chuuk has little remaining natural forest, most of these species would be a problem in secondary forests and agroforestry systems, as well.

During our visit local experts(3) showed us sites of known infestations. We also had available copies of various botanical and weed surveys conducted in the past (see Appendix 1, References). A visit of such short duration does not permit an exhaustive survey of the weed biota of the islands, and we only had time to visit three of the major islands in Chuuk lagoon. However, the intent was to conduct an initial, overall survey to assess major problems and opportunities. We were able to survey the islands of Weno (the main commercial center), Fefan and Tol. There may be a few invasive species that occur on other islands and not on the three that were surveyed. Surveys of additional islands or sensitive areas can and should be conducted as needed. This report summarizes our findings and makes some suggestions for further action.

For convenience and to be consistent with the Micronesia report, invasive species occurring in or of threat to Chuuk have been grouped into four 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 Chuuk (323 species).
2.  Species that are invasive elsewhere and are also invasive or potentially invasive on Chuuk (10 species).
3.  Species that are invasive or weedy elsewhere and are cultivated, common or weedy in Chuuk (80 species).
4.  Native species (or early introductions) that exhibit aggressive behavior (8 species).

These species are listed in Appendix 2. Additional information about each species is located on a World Wide Web site,, and on the PIER-CD.

There are a number of other species that are mostly invasive weeds in gardens, fields, and pastures and along roadsides but don’t seem to pose any particular threat to agroforestry or wildland ecosystems. While we did not specifically survey for them, a list of these species, compiled from the literature, is included in Appendix 3.

1. Dangerous species not known to be in Chuuk

A considerable number of invasive species have yet to reach Chuuk. These are listed in Appendix 2, Table 1. The worst of these include the following:

Cecropia obtusifolia and C. peltata, invasive tree species that are a problem in Hawai‘i and French Polynesia, respectively.

Cinnamomum verum (cinnamon), found to be very invasive in American Samoa and elsewhere. It is present on Pohnpei.

Clerodendrum chinense, a species that can form dense thickets that exclude other species. It tolerates shade well and suckers profusely.

Clidemia hirta (Koster’s curse), a serious problem species in Hawai’i and other locations. In Micronesia it is only present in Palau, but would be a serious problem if introduced as it grows well in the shade of closed forests.

Coccinia grandis (ivy or scarlet gourd), a smothering vine that is showing potential for serious damage to the forests of 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 a horticultural variety is present on Pohnpei. The proximity of the plant in Pohnpei and Guam poses a threat to Chuuk.

Cuscuta campestris (golden dodder), a parasitic plant quite prevalent on Guam.

Two rubber trees, Funtumia elastica (African rubber tree) and Castilla elastica (Panama rubber tree), species that have proven very invasive in Samoa. While not known to be present in Micronesia (Castilla elastica is present in Hawai‘i) and thus posing a lesser threat, their invasive nature makes these species prime candidates for prompt eradication if found.

Melaleuca quinquenervia (paperbark), a tree that favors wet or swampy areas. It is a major problem in Florida (US), where its spread is promoted by burning. It is present on both Guam and Pohnpei.

Miconia calvescens (the purple plague), which has caused serious damage to the ecosystem of Tahiti in French Polynesia. It has spread to other islands in French Polynesia and has also escaped in Hawai’i where it is the subject of an intensive and costly eradication effort. Recently it was discovered in northeast Queensland, Australia where eradication is also being attempted. It is an attractive garden plant and might be introduced this way or as tiny seeds on shoes or used equipment.

A number of grass species, including:

Mikania micrantha (mile-a-minute weed), a climbing vine that is very invasive in some locations in the Pacific, is present on Guam and has apparently been recently introduced to Kosrae.

Mimosa diplotricha [=invisa] (giant sensitive plant), absent from Chuuk but present on Pohnpei and Guam. Mimosa diplotrichais a particularly nasty plant as it is covered with thorns and forms dense tangles that are difficult to walk through. Chuuk is at high risk for invasion by this plant, as it is steadily making it way through the Pacific. Mimosa pudica, a smaller plant with only small prickles but forming dense mats, is already present.

Passiflora foetida (bombom) is present on Chuuk, but several invasive members of this invasive genus are absent, including:

Piper auritum (eared pepper, locally called "false sakau"), recently introduced to Pohnpei. This species suckers profusely and produces many small seeds that are spread by birds, rodents and bats. An attempt is being made to eradicate it on Pohnpei and it should not be introduced elsewhere. It was introduced into Pohnpei as a new form of sakau, but it is worthless in this regard.

Psidium cattleianum (strawberry guava), a small tree that forms dense thickets, is a major problem species in Hawai‘i, Tahiti and elsewhere. It is present in Pohnpei and thus is a serious threat to Chuuk.

Rubus spp., a number of which are problem species on tropical islands.

Solanum torvum (prickly solanum), a prickly bush that forms thickets.

Mucuna [Stizolobium] pruriens (cow itch or velvet bean), often introduced as a cover crop or to feed livestock. It is a climbing vine and has hairs that can cause severe itching. It is causing problems on Saipan and is present on Guam as well.

Thunbergia alata, T. grandiflora and T. laurifolia, climbing vines that are present on Guam.

Tibouchina herbacea (glorybush or cane ti), another species that is a major problem in Hawai‘i.

Triphasia trifolia (limeberry), invasive into forest edges on Guam.

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 an even better strategy, now being adopted by countries such as Australia and New Zealand, is to exclude all species not shown by risk analysis to be of negligible risk). Known problem species that have the potential to cause problems in tropical island ecosystems and are not yet present in Chuuk are listed in Appendix 2, Table 1. These species should be excluded through plant quarantine and, if establishment is detected, promptly evaluated for eradication. In addition, species that are present on Guam and Pohnpei but are not present in Chuuk are listed in Appendix 4. There is high risk of introduction of these species because of air and ship traffic between these points and Chuuk.

2. Species that are invasive elsewhere and are likewise invasive or have the potential to become so in Chuuk

Some known invasive plants that are causing trouble in similar ecosystems have been introduced into Chuuk (Appendix 2, Table 2). Some of them 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.

Adenanthera pavonina (the coral bean tree), invasive in secondary forests and seen on Weno and Fefan. The red beans are used in handicrafts.

Antigonon leptopus (chain of hearts). This climbing vine has become a widespread pest on Guam. We only saw it on Weno, so it may have not yet spread to other islands. People like to plant it because it has pretty flowers.

Chromolaena odorata (Siam weed, local name otuot), a highly invasive pan-tropical weed. It was seen on Weno and Tol and will likely become even more widespread over time. Biological controls are available that are effective in open areas, less so in shaded stands.

Clerodendrum quadriloculare, seen on all the islands we visited, is an undesirable species because it appears to have the ability to invade intact or relatively intact forests. A dense, monospecific understory of this species was seen growing in full shade beneath the forest canopy on Pohnpei, making it a likely candidate to invade intact or only slightly disturbed forest stands. It is notorious for being a prolific producer of root suckers and in fact the plant is easily propagated by means of root cuttings. Specimens observed on Chuuk were mostly cultivated ones in yards, but on Fefan we saw a plant that had suckered profusely and was causing problems in an agroforestry garden. Further planting of this species should be discouraged and people owning plants may wish to destroy them rather than fighting the suckers that will invariably come up in their yards or gardens. We can furnish information on control measures.

Dieffenbachia seguine (spotted Dieffenbachia or dumb cane) was seen both as an ornamental and naturalized on Weno. This is potentially a troublesome species, as it reproduces vegetatively and can thrive in the dense shade of an intact forest canopy.

Hedychium coronarium (white ginger) can be an invader of swampy areas and wet forests.

Occasional trees of Paraserianthes falcataria [Falcataria moluccana] (Molucca albizia) were seen on Weno. This species has the potential, over time, of spreading widely through the forest (as can be seen on Pohnpei). Further planting should be discouraged. If this is not a desired species, emphasis could be given to cutting the existing trees.

Spathodea campanulata (African tulip tree), a commonly planted ornamental present on Pohnpei and Guam as well as Weno Island, Chuuk. This tree has become a major problem in Fiji, the Hawaiian Islands and some other places. Large trees are dangerous because of falling branches. It was only seen in a few places on Weno (around the hospital, the Governor’s office and on the causeway). It would be best not to plant it any more on Weno, discourage any planting on the outer islands, and work to replace the present trees with a better species over time. .

Syngonium angustatum, a climbing aroid, is probably another escape from cultivation. Like Dieffenbachia maculata, it has the ability to spread in the deep shade of intact forests. It is difficult to eradicate by hand as it is able to reproduce from a single node and bits and pieces of the stems or roots are easily overlooked.

Tradescantia spathacea (oyster plant, boat plant, boat lily, moses-in-a-boat), reported to be present on Pis and Satawan, can invade the forest understory.

3. Species that are mentioned or listed as weedy or invasive elsewhere and are cultivated, common or weedy in Chuuk

A large number of other cultivated, 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 2, Table 3) should be monitored for spread and possible control, if necessary.

Invasive or potentially invasive tree species include Acacia auriculiformis (earleaf acacia), Albizia lebbeck, Bauhinia monandra (orchid tree), Ceiba pentandra (kapok), Delonix regia (flame tree), Leucaena leucocephala (tangan-tangan), Pithecellobium dulce (Madras thorn), Samanea saman (monkeypod), and Tecoma stans (yellow bells).

A number of introduced grasses have become established, including Cenchrus echinatus (bur grass); Chloris barbata (swollen fingergrass), Chloris radiata (plush-grass, radiate fingergrass), Cynodon dactylon (Bermuda grass), Digitaria ciliaris (fingergrass, smooth crabgrass), Digitaria violascens (smooth crabgrass), Eleusine indica (goose grass), Paspalum conjugatum (Hilo grass), Paspalum paniculatum (Russell River grass), Pennisetum polystachion (mission grass, locally called mechenkatu) and Saccharum spontaneum (wild cane).

Bidens pilosa (beggar's tick) was prevalent on Weno and Fefan, but apparently has not yet made its way to Tol.

Desmanthus virgatus is quite widespread and weedy.

Ipomoea aquatica (aquatic morning glory) was seen choking a drainage ditch at the airport. Eichhornia crassipes (water hyacinth) is also reportedly present but was not seen.

Ipomoea carnea subsp. fistulosa was seen in cultivation and there appeared to be some naturalizing.

Lantana camara (Lantana) occurs on several of the Chuuk islands. Village leaders on Tol stated that they were concerned about its weed potential there.

Passiflora foetida (love-in-a-mist) is common but not overly aggressive.

Sansevieria trifasciata is quite widespread on Weno. It is difficult to control as it spreads by rhizomes.

Stachytarpheta cayennensis [urticifolia] (blue rat's tail, local names sakura or ouchung) and Stachytarpheta jamaicensis were both widespread.

Wedelia [Sphagneticola]  trilobata (Singapore daisy, locally referred to as "sunflower" on Weno) is a widespread pest, as on many Pacific islands.

4. Native species (or early introductions) exhibiting aggressive behavior

Some native species (or early introductions) exhibit aggressive characteristics. These species are listed in Appendix 2, Table 4. Merremia peltata is quite invasive any place there is disturbance, as it is throughout Micronesia.

Strategies for dealing with invasive species

The first line of defense against invasive species is to keep them out. Control at ports of entry is essential, and land management officials should work closely with plant protection and quarantine officials to exclude known and potential invasive plant species. Plant quarantine officers are familiar with most agricultural pests, but they may not be aware of some of the pests that threaten wildland ecosystems. In cooperation with the plant quarantine organization, a list of 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 go to the approach recently adopted by Australia and under serious consideration by a number of other countries. That is to exclude all alien species not shown to be of negligible 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.

Education of the public about the danger of introductions and encouraging the use of native species can be helpful. People need to understand why they should follow the quarantine regulations, why they shouldn’t dump garden cuttings in the woods, and why they should report suspicious plants. What may just be a pretty flower to be planted in a yard or garden can turn out to be an invasive 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.

The public also needs to understand that the immediate eradication of a small area of a problem species, even if it involves the use of herbicides, may be better than living with a problem species forever. There are many instances where you hear people say "I wish we'd taken action when this pest was first noticed". It may even be worthwhile to take people to a place where they can be shown the full extent of a problem if the infestation is allowed to spread so that they will accept and support eradication. For example, anyone visiting Tahiti would very likely come away convinced that Miconia calvescens is an ecological disaster and that it should be prevented from becoming established on other Pacific islands.

The public should also be encouraged to report suspicious plants. Public service announcements on television or radio or newspaper articles can encourage this. Funding can be requested to prepare public service announcements or "wanted" posters. Prompt follow-up to public reports is essential to maintain credibility.

It is particularly important to work with any local nurseries or plant importers, as these are often 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.

Foresters, conservation officers, extension agents and others that spend time in the field should be alert to new species that exhibit invasive behavior. Often, these species first show up in urban or farm areas and tend to first become established 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 and Aliens list-servers.

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 lands or to take action on private lands if the landowner cannot be located or does not take prompt action. Provision for emergency funds to deal with immediate problems should also be in place. Model laws and regulations can be obtained from states and countries that have implemented them.

The Federated States of Micronesia and Chuuk State governments are encouraged to take advantage of the Federal assistance programs in dealing with invasive plant species. Cost-share funding is available 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 consultation. Finally, cost-share funding can be requested to deal with forest health problems, including plant pests, 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 would undoubtedly take precedence over the chronic problem of a species that has escaped control.


In addition to the above strategies, we offer the following specific recommendations:

Since there is traffic to Chuuk from both Guam and Hawai‘i, where many of these species are present, it would be highly desirable to institute special measures to prevent introduction of invasive species from these sources. At a minimum, quarantine officers should be alert to people who might have been in the woods or rural areas in Guam or Hawai‘i, especially on the Big Island of Hawai‘i, and inspect their shoes or boots for seeds. Any trucks or equipment coming from Hawai‘i that have been used in rural areas must be power washed or steam cleaned, and this would be highly desirable for equipment from Guam as well. Warning posters should be produced to alert the public and encourage reporting of any introductions. Any infestations picked up from public reporting or scouting should be promptly eradicated before the plants set seed.

Appendix 1.  References

Appendix 2. Species by category

Appendix 3.  Other invasive plant species, mostly of agricultural concern, reported to be present in Chuuk

Appendix 4. Invasive species present in Guam or Pohnpei but not present in Chuuk

Appendix 5. Scientific name synonyms

(1)  Former Director, Pacific Southwest Research Station, USDA Forest Service (now retired); Botanist, Australian Quarantine and Inspection Service; Research Ecologist/Team Leader, Institute of Pacific Islands Forestry, USDA Forest Service; Forest Health Coordinator, Institute of Pacific Islands Forestry, USDA Forest Service and Chief of Livestock, Chuuk Department of Agriculture, FSM, 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 thank Nario Innocente, Director, and Thomas Mazawa, Chief of Livestock, Chuuk Department of Agriculture and Troy Larsen, Peace Corps Volunteer, for their hospitality and generous assistance in the conduct of the survey.

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This page updated 14 January 2001.