Preventative measures: A Risk Assessment of Carpobrotus edulis for Hawaii and other Pacific islands was prepared by Dr. Curtis Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service. The alien plant screening system is derived from Pheloung et al. (1999) with minor modifications for use in Pacific islands (Daehler et al. 2004). The result is a score of 9.5 and a recommendation of: "Likely to cause significant ecological or economic harm in Hawaii and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawaii and/or other parts of the world."
Physical: Manual methods appear to be the most effective means of controlling C. edulis at this stage. Albert (1996; in PIER, 2005) recommends: "Hand-pull individual plants and remove any buried stems. Mulch to prevent re-establishment. Large mats can be removed by rolling them up like a carpet". It is important to remove any C. edulis remains during eradication, as any remains left in place become a focus of regeneration, due to the large number of seeds which survive in the fruit for a long time (Fraga et al. 2006).
Another thing to keep in mind following removal of C.edulis is that secondary plant invaders can take advantage of opened areas, spreading rapidly and impeding restoration efforts in coastal dune habitats. C. edulis leaves behind a layer of debris of dead and decaying organic matter that accumulates under the plant. This tends to be left behind after C. edulis is removed. Within the debris are often the dormant seeds of invasive grasses, and these sprout after C. edulis is removed, benefiting from the accumulation of nutrients in the area that C. edulis has facilitated. To avoid this it may be best to selectively remove C. edulis to ensure that some is left behind to stabilise the soil and minimise sand movement into the area. Once the area has been restored to a more natural community, the remaining C. edulis can be removed and that area restored in turn (Kim, undated).
Chemical: PIER (2005) suggest the use of glyphosate herbicides. Schmalzer and Hinkle (1987) reported that there had been no comprehensive survey of herbicide effects on C. edulis. It is assumed that broad spectrum herbicides would kill C. edulis but they may also impact adjacent vegetation. Chlorflurenol, a morphactin, has been used to reduce growth of C. edulis along roadways (Hield and Hemstreet, 1974; in Schmalzer and Hinkle, 1987).
Biological: The options for biological control are currently limited, as the pathogens which attack C. edulis are not specific to it. Verticillium wilt can cause considerable damage (McCain et al. 1974), but using it could cause problems as it also attacks commercial crops (Schmalzer and Hinkle, 1987). Suehs et al. (2004b) state that a constraint on seed production or germination would be the most efficient way to control C. edulis on a long-term basis, if possible, due to its high success in these domains. Two introduced scale insects caused widespread mortality of Carpobrotus edulis plantings in California in the 1970s (Donaldson et al. 1978). As a result the California highway Department introduced natural enemies to control iceplant scale (Tassan et al. 1982). Nonetheless, scale insects have been observed to cause death of clones in California and could be more widely promoted in natural settings.
Location Specific Management Information
The California Exotic Pest Plant Council (CalEPPC) have placed C. edulis on their A-1 list (Grossinger et al. 1998).
Di Tomaso (2005) suggests planting alternative species to C. edulis in California - such as Delosperma cooper (hardy iceplant), Osteospermum fruticosum and hybrids (freeway daisy), Teucrium chamaedrys or T. lucidrys (wall germander) or Drosanthemum floribundum (showy dewflower).
Carpobrotus carpobrotus x edulis is being removed by the MOD in the Windmill Hill flats area. The Upper Rock Management Plan recommends legislation prohibiting growing or keeping of this species in gardens and homes within the reserve (Perez and Bensusan, undated in Varnham, 2006).
Early attempts at controlling Carpobrotus edulis in Minorca began in the late 1990s, with the aim of eradicating the plant from Favaritx (in the north-east of the island). This was not achieved due to landowner opposition. Eradication measures were simultaneously carried out in the east of the island by the local NGO Grup d'Ornitologia Balear i Defensa de la Naturalesa.
Subsequent to these early attempts, further preparatory measures were carried out to enhance the success of further efforts. A detailed cartography regarding the distribution of the plant was undertaken, and experimental methods investigated to determine the best means of eradication and restoration. These revealed that the plant covered 25.8ha of the island, and that the most efficient eradication method was manual removal. Eradication was finally undertaken between 2002 and 2005. An awareness campaign was also launched, to ensure its ongoing success. Alternative plants for gardening were suggested. Today the plant is restricted to two zones in the north east of the island, due to opposition of landowners to its removal (Fraga et al. 2006).
Carpobrotus edulis was eradicated from Ramla I-Hamra, Malta in 2001. The invasion was in the early stages when the eradication was carried out by the former Environment Protection Department, using manual methods (IUCN, 2005).
Carpobrotus edulis was eradicated from Ramla tat-Torri, Malta in c.1997/99. The invasion was partly extensive but not considered serious at the time of eradication. The eradication was carried out by the former Environment Protection Department, and involved manual methods. It caused some initial disturbance, but also contributed to the expansion of the Centaureo-Ononidetum fixed dune community (IUCN, 2005).
1. Donaldson, D.R., Moore, W.S., Koehler, C.S. and Joos, J.L. 1978. Scales threaten iceplant in Bay Area. California agriculture. October. P. 4-7.
4. Fraga, P., Estaun, I., Olives, J., Da Cunha, G., Alarcon, A., Cots, R., Juaneda, J. and Riudavets, X. 2006. Eradication of Carpobrotus (L.) N.E. Br. in Minorca.
Summary: This paper reports on the eradication of Carpobrotus edulis from the majority of Minorca in the Balearic Islands.
Available from: http://www.iucn.org/places/medoffice/invasive_species/case_studies/eradication_carpobrotus_minorca.pdf [Accessed 16 August 2006]
8. Suehs, C.M., Affre, L. and Medail, F. 2004b. Invasion dynamics of two alien Carpobrotus (Aizoaceae) taxa on a Mediterranean island: II. Reproductive strategies. Heredity. 92: 550-556.
Summary: This paper discusses the reproductive strategies of two species of Carpobrotus in the Mediterranean region.
9. Tassan, R.L., Hagen, K.S. and Cassidy, D.V. 1982. Imported natural enemies established against iceplant scales in California. California Agriculture 36: 16-17.
Summary: This paper provides a brief history of the introduction of two hymenopteran wasps to control iceplant scale in California and describes early ‘successes’ in the establishment of these wasps.
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