Report to the Republic of Palau: 2008 update on Invasive Plant ...

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een planted on Babeldaob and is reproducing. Much more prolific reproduction can be expected if a fire occurs. It has a weed risk assessment <strong>of</strong> 15, “high risk”. Melia azedarach (Chinaberry, pride-<strong>of</strong>-India, Indian lilac) seedlings were seen beneath and around cultivated plants at a residence and a business in Airai in <strong>the</strong> 2002 survey. It was also seen in cultivation on Koror. Several seedlings were also noted in Koror that appeared <strong>to</strong> be selfsown, but <strong>the</strong> source was not immediately apparent. In this survey, <strong>the</strong> species was noted in cultivation on Malakal (in <strong>the</strong> gardens near <strong>the</strong> radio <strong>to</strong>wer), at several additional residences in Airai and on Ngercheu Island (Carp Resort). This species is a prolific producer <strong>of</strong> seed, which is spread by birds. In <strong>Palau</strong>, it apparently begins <strong>to</strong> flower at a very young age. It is invasive in a number <strong>of</strong> Pacific locations, including <strong>the</strong> Cook Islands, French Polynesia and Hawai‘i as well as in South Africa. It is a “high risk” species with a weed risk assessment score <strong>of</strong> 14. 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’An<strong>to</strong>nio and Vi<strong>to</strong>usek, 1992) and it is reported as a serious threat <strong>to</strong> forests in Brazil (C. Martins, pers. comm.). It was reported present by Fosberg et al. (1979). Raulerson et al. (1996) reported it present on Babeldaob but rare. We found it on <strong>the</strong> north extension <strong>of</strong> <strong>the</strong> Compact Road in Ngaraard State. An Australian weed risk assessment gives this species a score <strong>of</strong> 7, indicating it is <strong>of</strong> high risk. Panicum maximum [=Megathyrsus maximus, Urochloa maxima] (Guinea grass), while not yet widespread in <strong>Palau</strong> (it is present on Koror and Babeldaob), is ano<strong>the</strong>r grass that can help perpetuate a fire cycle. It seeds pr<strong>of</strong>usely and <strong>the</strong> seeds are dispersed by wind, birds (e.g. chestnut mannikins) and flowing water or as a contaminant. It can survive long periods <strong>of</strong> drought. Fire will sweep through stands <strong>of</strong> 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. Its weed risk assessment score is 17, “high risk”. Pennisetum setaceum (fountain grass) was found in cultivation at two residences in Airai and a resort in Ngerkebesang in 2002 but was not seen in <strong>2008</strong>. It is an attractive ornamental but it can produce large amounts <strong>of</strong> wind-dispersed seed. While it is most likely <strong>to</strong> be invasive in dry areas, it could possibly spread in <strong>Palau</strong>. It is a serious problem species on dryer sites in Hawai‘i. It has a weed risk assessment score <strong>of</strong> 26, “high risk”. Pereskia aculeata (Barbados gooseberry, leafy cactus) was found on Ngercheu Island (Carp Resort). It is invasive in Queensland, Australia, particularly in riparian areas, forming large, impenetrable clumps. It is a declared noxious weed in South Africa, where it has become a problem in forestry and conservation areas. Seed is bird-dispersed and it can also spread from stem fragments. Its weed risk assessment indicates that it is <strong>of</strong> high risk, with a score <strong>of</strong> 13. 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 <strong>to</strong> be widespread but not presently abundant on Guam. These species may have been accidentally introduced as a result <strong>of</strong> military activity as both were also 16
introduced <strong>to</strong> Penrhyn Island (Cook Islands) when an airfield was built <strong>the</strong>re during <strong>the</strong> Second World War (Bill Sykes, pers. com.) and are present elsewhere in <strong>the</strong> Pacific where military airfields were constructed. Pluchea indica is found along <strong>the</strong> seashore and inland on poorer sites on both Peleliu and Angaur while P. carolinensis is located along <strong>the</strong> airstrip on Peleliu. Pi<strong>the</strong>cellobium dulce (kamatsíri, opiuma, Madras thorn) is a thorny tree that is a problem species in Hawai‘i. It is present on many <strong>of</strong> <strong>the</strong> major islands <strong>of</strong> Micronesia, but doesn’t seem <strong>to</strong> be a serious problem. The seeds are bird-dispersed and its sap can cause eye irritation and skin welts. It is relatively resistant <strong>to</strong> fire and resprouts rapidly by basal or aerial shoots. It was reported cultivated on Koror by Fosberg et al. (1979) but that tree has not been seen in recent surveys. A planted tree was seen in Airai during this survey. Its weed risk assessment gives it a score <strong>of</strong> 14 and rates it “high risk”. Psidium cattleianum (strawberry guava), a small tree that forms dense thickets, was previously reported <strong>to</strong> be present on Koror (Fosberg et al., 1979), perhaps in cultivation, but was not found during this or <strong>the</strong> previous survey. It is a major problem species in a number <strong>of</strong> island ecosystems including Hawai‘i and Tahiti in <strong>the</strong> Pacific and La Réunion and Mauritius in <strong>the</strong> Indian Ocean. Varieties with red and yellow fruits are known. Birds and pigs (and possibly fruit bats as well) disperse <strong>the</strong> seeds. This is an extremely dangerous species with a weed risk assessment score <strong>of</strong> 18. Solanum <strong>to</strong>rvum (prickly solanum, devil’s fig) is a large spiny shrub <strong>of</strong> disturbed areas and fields that can form dense, impenetrable thickets. Its seeds are bird-spread. The principal infestation (apparently a number <strong>of</strong> individual plants) is in and around Nekken in Ngatpang and Aimeliik States, Babeldaob. A leaf-eating chrysomelid beetle, Leptinotarsa undecimlineata, is reported <strong>to</strong> be host-specific (Waterhouse and Norris, 1987) but would probably not be effective on <strong>the</strong> scattered plants found on Babeldaob. Syngonium angustatum (arrowhead plant, goosefoot plant), a climbing aroid, is widely cultivated in <strong>Palau</strong>, particularly in Koror and Airai States, and a number <strong>of</strong> escapes were noted both in this and <strong>the</strong> previous survey. This species has <strong>the</strong> ability <strong>to</strong> spread in <strong>the</strong> deep shade <strong>of</strong> intact forests, forming a dense mat on <strong>the</strong> forest floor as well as climbing trees. It is difficult <strong>to</strong> eradicate as it is able <strong>to</strong> 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. An almost identical species, Syngonium podophyllum, has a weed risk assessment score <strong>of</strong> 15, “high risk”, that can also be applied <strong>to</strong> this species. Syzygium cumini (mesekerrák, Java plum) is reported <strong>to</strong> be present, perhaps in cultivation, on Koror, Babeldaob and Aulupse‘el (Rock Islands) (Fosberg et al., 1979; Raulerson et al., 1996) but was not seen in ei<strong>the</strong>r this or <strong>the</strong> 2002 survey. It was seen on several <strong>of</strong> <strong>the</strong> Rock Islands (including Bukrairong) by <strong>the</strong> second author in Jan. <strong>2008</strong> and appeared <strong>to</strong> be established but not particularly invasive. This species is invasive in <strong>the</strong> Cook Islands, Hawai‘i and French Polynesia (Raiatea). Two small plants <strong>of</strong> Tephrosia candida (white tephrosia) were found in Aimeliik State on Babeldaob in 2002 and <strong>the</strong>re are voucher specimens in <strong>the</strong> Bishop and Belau National Museums. 17
Page 1: Report to<
Page 4 and 5: Pulo Ana ..........................
Page 7 and 8: Report to<
Page 9 and 10: of known or potent
Page 11 and 12: Leucas lavandulifolia [voucher 9929
Page 13 and 14: Rock Islands We were especially int
Page 15 and 16: 2. Species that are subjects <stron
Page 17 and 18: Clidemia hirta (kúi, Koster’s cu
Page 19 and 20: Timonius timon (Liberal) is widespr
Page 21: cultivation but this tree-climbing
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Page 27 and 28: lathyroides (cow pea, phasey bean),
Page 29 and 30: Cestrum diurnum (day cestrum, day j
Page 31: Piper auritum (eared pepper, also c
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Page 36 and 37: Agriculture invasive species <stron
Page 38 and 39: Table A. Priority species for exclu
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Appendix 2. Invasive plant species
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Table 1. Invasive plant species <st
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Table 2. Other inv
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Appendix 3. Invasive species presen
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Scientific Name Hawai'i Guam Yap Pa
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Appendix 5. Other
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Table 1. Other inv
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Table 2. Other inv
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Table 2. Other inv
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Table 3. Other inv
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Table 5. Other inv
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Table 6. Other inv
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Table 8. Other inv
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Appendix 6. Presence of</st
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Table 2. Species of</strong
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Table 1. Other spe
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Table 2. Other spe
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Table 9. Other spe
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Appendix 8. Risk assessments for in
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Synonym Listed as Family Gomphrena
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Fosberg, F. R., and M.-H. Sachet. 1
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Stoddart, D. R. 19
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