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

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walk through. It is present in a number <strong>of</strong> South Pacific locations (American Samoa, Cook Islands (Aitutaki), Fiji, French Polynesia (Society Islands), New Caledonia, Niue, Papua New Guinea, Solomon Islands and Vanuatu). Biological control agents were reportedly introduced <strong>to</strong> <strong>Palau</strong>, but it is not known if <strong>the</strong>y have become established. If present, <strong>the</strong>y seem <strong>to</strong> be having little effect. It is fairly common on Babeldaob and a number <strong>of</strong> infestations were noted along <strong>the</strong> Compact Road. The species is only present <strong>to</strong> a limited extent on Angaur and is absent from Peleliu. It has a weed risk assessment score <strong>of</strong> 24, “high risk”. Mimosa pudica (sensitive plant), a smaller plant than M. diplotricha with only small thorns, is common throughout <strong>Palau</strong> (except Peleliu) as a component <strong>of</strong> <strong>the</strong> weedy vegetation <strong>of</strong> roadsides and o<strong>the</strong>r disturbed areas. It has a weed risk assessment score <strong>of</strong> 18, “high risk”. 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. Its weed risk assessment score is 11, “high risk”. Psidium guajava (guabang, kuabang, guava) is common in cultivation and is occasionally present as naturalized plants, but nothing like <strong>the</strong> dense stands seen in Tonga. This is a major invasive species in Tonga and <strong>the</strong> 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 <strong>the</strong> seeds. However, in <strong>Palau</strong> it does not seem <strong>to</strong> be any more common than in 2002 even though it has a “high risk” weed risk assessment score <strong>of</strong> 21. Sphagneticola [=Wedelia] trilobata (ngesil ra ngebard, Singapore daisy) has become a serious pest on many Pacific islands (Thaman, 1999) as well as in nor<strong>the</strong>rn Australia. It is both planted and naturalized at a number <strong>of</strong> locations throughout <strong>Palau</strong>. 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 <strong>of</strong>ten leaves numerous nodes that freely root and rapidly spread. Mowing or slashing can make <strong>the</strong> problem worse unless done very frequently and very close <strong>to</strong> <strong>the</strong> ground. Its weed risk assessment score is 13, “high risk”. Tecoma stans (yellow bells, yellow-elder, yellow trumpetbush) is widely cultivated in <strong>Palau</strong>. It is a serious invader <strong>of</strong> disturbed areas in Tonga and French Polynesia where it grows in dense stands, commonly with o<strong>the</strong>r weedy species. The seeds are wind-dispersed. However, only isolated individuals were seen outside <strong>of</strong> cultivation. It is a “high risk” species with a weed risk assessment score <strong>of</strong> 8. Thunbergia grandiflora (bung el etiu, blue trumpet vine, Bengal trumpet) is an aggressive vine that can smo<strong>the</strong>r trees. The plant forms large underground tubers and is difficult <strong>to</strong> eradicate because <strong>of</strong> regeneration from <strong>the</strong> tubers and root and stem fragments. It is a problem species in Australia (a noxious weed in Queensland) and Singapore. It has a weed risk assessment score <strong>of</strong> 11, “high risk”. There were formerly a number <strong>of</strong> examples in <strong>Palau</strong>, including a very large infestation in Koror, but its presence has been reduced by control action since <strong>the</strong> 2002 survey. However, much work remains <strong>to</strong> be done on this plant. 12
Timonius timon (Liberal) is widespread on Angaur and Peleliu. Individual trees and small stands were found on a number <strong>of</strong> <strong>the</strong> Rock Islands. It was probably introduced <strong>to</strong> Angaur and Peleliu during or shortly after World War II and has since spread <strong>to</strong> <strong>the</strong> Rock Islands. Several individual trees and an apparently reproducing infestation were located on Babeldaob. Single trees (possibly planted) were previously observed on Kayangel and Ngerkebesang. It is an invader <strong>of</strong> open, disturbed areas. As time goes by, it seems <strong>to</strong> be over<strong>to</strong>pped and replaced by native species, and it seems <strong>to</strong> be less prevalent on Angaur and Peleliu than formerly as <strong>the</strong>se forests have become more mature. Its presence in <strong>the</strong> Rock Islands indicates that it is spreading <strong>to</strong> <strong>the</strong> north and, unless checked, will probably eventually reach Koror and Babeldaob where it would probably be an invader in open and disturbed areas and potentially hybridize with endemic species <strong>of</strong> Timonius. Tradescantia spathacea (kobesos, oyster plant, boat plant, boat lily, Moses in a boat) and T. zebrina (wandering jew) are planted as ornamentals in <strong>Palau</strong> but have escaped in several instances. Several examples <strong>of</strong> Tradescantia spathacea invading <strong>the</strong> forest unders<strong>to</strong>ry were seen on Peleliu. A fairly large patch <strong>of</strong> naturalized Tradescantia zebrina can be seen in Ngiwal State, Babeldaob, as well as on Angaur. There is a small naturalized patch on Kayangel. These plants are commonly spread through <strong>the</strong> dumping <strong>of</strong> garden cuttings. Turnera ulmifolia (yellow alder, sage rose) is widely planted as an ornamental. Naturalization was noted at a number <strong>of</strong> locations. The seed is reported <strong>to</strong> be carried by ants (Staples et al., 2000) and <strong>the</strong> species is widely naturalized in <strong>the</strong> tropics. A related species, Turnera subulata (white alder), was also noted in cultivation. This species is somewhat weedy in Malaysia and has a weed risk assessment score <strong>of</strong> 10, “high risk”. Invasive species <strong>of</strong> limited extent The following species are limited in extent or have recently become established. Some <strong>of</strong> <strong>the</strong>m are only in limited cultivation and could be eradicated at minimal cost. O<strong>the</strong>rs may be candidates for control action or should just be moni<strong>to</strong>red for possible future action, if necessary. See <strong>the</strong> recommendations section for species-specific recommendations. Acacia [=Vachellia] farnesiana (Elling<strong>to</strong>n curse, klu, sweet acacia) was seen at one location in cultivation in Airai State, Babeldaob, during <strong>the</strong> 2002 survey. This thorny shrub is a pest in Fiji, French Polynesia, New Caledonia, Solomon Islands and Vanuatu and has a “high risk” weed risk assessment score <strong>of</strong> 14. Alternan<strong>the</strong>ra brasiliana (Brazilian joyweed, Joseph’s coat) is planted as an ornamental and occasional escapes were seen. It is invasive in Queensland, Australia. Antigonon lep<strong>to</strong>pus (dilngau, chain <strong>of</strong> love), a climbing vine <strong>of</strong>ten planted as an ornamental, is a widespread pest on Guam. Although this species has been subject <strong>to</strong> control action, several examples, mostly in cultivation, were seen in Koror. It is a “high risk” and difficult <strong>to</strong> remove species with a weed risk assessment score <strong>of</strong> 19. A few examples <strong>of</strong> Asparagus densiflorus (asparagus fern, sprengeri fern) were seen, all in cultivation (<strong>of</strong>ten in hanging baskets). Asparagus densiflorus has recently been found <strong>to</strong> be 13
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Page 4 and 5: Pulo Ana ..........................
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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
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Page 17: Clidemia hirta (kúi, Koster’s cu
Page 21 and 22: cultivation but this tree-climbing
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Page 29 and 30: Cestrum diurnum (day cestrum, day j
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Page 61 and 62: Appendix 1. Invasive plant species
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Table 4. Other inv
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Table 4. Other inv
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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 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 3. 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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