Preventative measures: A Risk assessment of Chromolaena odorata for the Pacific region was prepared by Pacific Island Ecosystems at Risk (PIER) using the Australian risk assessment system (Pheloung, 1995). The result is a score of 34 and a recommendation of: reject the plant for import (Australia) or species likely to be of high risk (Pacific).
Using a revised climate model (Kriticos et al. 2005) of the estimated potential distribution of C. odorata it was predicted that mediterranean, semi-arid and temperate climates are unsuitable for its establishment. Much of tropical Africa, the north-eastern coast of Australia and most Pacific islands are at risk of invasion. The distribution of C. odorata in South Africa extends further south than predicted by the model based on Asian and American distribution records, supporting the claim that the South African variety of C. odorata has different climatic requirements to the varieties elsewhere (EPPO 2005).
Physical: Manual slashing and use of bush-cutter or tractor-drawn implements are commonly used methods of control. Slashing causes regeneration unless followed by other control methods. Manual weeding is labour intensive. The use of tractor drawn equipment is limited to areas that are accessible (Ecoport).
Chemical: Chemical control using herbicides applied at the seedling stage or on regrowth has given encouraging results. Triclopyr has proven to be the most effective. However, problems in herbicide use include the high cost of the chemicals and their application, ecological concerns and, non-compatibility in many cropping and other environmental situations (Ecoport). Removing seed and flower heads and spraying with 2,4-D Amine plus Picloram (Tordon in Australia) kills top growth and (picloram kills the root system is recommended (Rod Randall, pers. comm. 2000).
Biological: The biological control agent Pareuchaetes pseudoinsulata has been introduced into Guam, where it effectively defoliates pure stands. It is less successful in scattered plants and patches. It has also been introduced into Palau, Kosrae, Pohnpei, Yap and Saipan Island (Mariner Islands) where it has been effective in reducing C. odorata. It has also been released on Sumatra, Indonesia, where it is effective in reducing densities of the weed. Releases into other parts of Indonesia appear to have failed.
Another species, the stem gall fly Cecidochares connexa (originally collected from C. odorata in Mexico, Brazil and Bolivia Cruttwell 1974) is a suitable biological control agent for C. odorata (Cruttwell McFadyen Chenon and Sipayung 2003). Most gall-forming species of the tephritid genera Cecidochares Bezzi are highly host specific, sometimes attacking only a single plant species (Foote et al. 1993, in Cruttwell McFadyen Chenon and Sipayung 2003). Based on the results of host testing of C. connexa was granted Indonesian Government allowance for field release in 1995 and is now established on most of the larger Indonesian islands (Tijitrosemito 2002, Wilson and Widayanto 2002, in Cruttwell McFadyen Chenon and Sipayung 2003). Since then it has been released in Palau, Papau New Guinea and the Philippines (Esguerra 2002, Orapa et al. 2002, in Cruttwell McFadyen Chenon and Sipayung 2003; Dr. Muniappan, pers. comm.). Die-back and death of plants have been recorded at many sites within 3 to 5 years of release, especially in low altitude sites (less than 300m) with a short dry season (Cruttwell McFadyen Chenon and Sipayung 2003). At higher altitude sites (over 600m) or where cloudy conditions, cold temperatures or long dry seasons limit the number and activity of flies control is slower and less adequate (Cruttwell McFadyen Chenon and Sipayung 2003).
Location Specific Management Information
An eradication programme has been in place since c.1994.
The removal of Chromolaena odorata has the potential to lead to an increase in the similarly invasive Lantana camara, by providing an opportunity for an increase in cover.
Papua (Irian Jaya)
Under an ACIAR program with Indonesia, a stem-gall fly Cecidochares connexa was released as a biocontrol agent against Chromolaena odorata in about 1996-97 in Jayapura in Papua. It established readily and is spreading, and is I believe resulting in effective control of the weed in the release areas. This gall fly can be readily distributed to new areas by cutting 10 cm lengths of stem with large galls containing mature larvae, and simply putting these out among bushes in the new area. This should be done during the wet season but not before flowering, as the adults won't lay in flower buds. Flowering is probably July in Papua, therefore the last date for releases would be about March. Further information on this program or on the gall fly can be got from me or from email@example.com .The same agent has been released in Papua New Guinea and several islands of the Marianas and Pacific (McFadyen R. Pers. Comm., July 2003).
Subject of an eradication program in Queensland, Australia.
South AfricaWe are experiencing technical difficulties and unable to complete your request. Please try later.
C. odorata is a declared noxious weed in South Africa.
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