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Acacia mearnsii (tree, shrub)  |
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Management Information
Preventative measures: A Risk Assessment of
Acacia mearnsii for Hawi 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 15 and a recommendation of: "Likely to cause significant ecological or economic harm in Hawai‘i and on other Pacific Islands as determined by a high WRA score, which is based on published sources describing species biology and behaviour in Hawai‘i and/or other parts of the world."Chemical: Saplings sensitive to foliar applications of triclopyr. Dicamba, glyphosate and picloram applied cut-surface effective, triclopyr probably effective, although applications to drilled holes in larger trees probably necessary. Cut-surface (notching) applications of picloram provided complete control, glyphosate and dicamba caused 80% control, and 2,4-D was inadequate at Kala’e, Molokai. Alton Arakaki (Univ. Hawai‘i) and Ed Misaki of the Nature Conservancy (TNC) confirmed the efficacy of picloram but got much better results with glyphosate and dicamba, each resulting in over 90% control at Kamakou Preserve. Basal bark and stump bark treatments with 2,4-D or triclopyr effective. Pat Bily (TNC) reported that basal bark applications with triclopyr ester at 20% in oil was effective, as was cut stump application of triclopyr amine at 50% in water. Hawai‘i Volcanoes National Park (HAVO) staff got good control with triclopyr amine at 10% in water applied to cut stumps (Chris Zimmer, HAVO). Anecdotes indicate that wattle is sensitive to basal bark treatment with diesel alone and to girdling. (Motooka et al., 2002, PIER 2003). Biological: The use of Cecidomyiidae gall midges to inhibit reproduction of Acacia species is being researched for use in South Africa. A Dasineura sp. has been identified as a promising control agent as it prevents fruit formation (and thus reproduction) without affecting vegetative growth (which may be a concern for industries or commerce that rely on the species). Dasineura is also known to have a narrow host range. Melanterius maculatus, a seed-eating weevil (native to Australia), was introduced into South Africa in 1993 and caused reductions in Acacia mearnsii seed numbers in some areas. Larvae feed on developing seeds inside the pods and adults feed on the green pods and pinnules. In South Africa a local stump-colonising fungus has been isolated and added to cut trees to prevent regrowth. Finally, a wasp (Bruchophagus acaciae) has been described that attacks the seeds of some Acacia species but not those of Acacia mearnsii (Adair et al., 2000; Adair, 2002; ARC-PPR, 2003; Hill, Gordon and Neser, 1999). Integrated management: The Working for Water programme implemented by the South African Government is a collaborative program that aims to ameliorate the problems caused by Acacia species and other invasive plants. The program consists of more than 30 sub-projects in eight provinces in the country and consists of the clearing of weeds from water courses (by mechanical and chemical methods). Between 1995 and 2000 over $100 million of poverty-relief funds on the program which was labor intensive and provided job oppurtunities for local communities. After seven years of implementation of the project it became clear that rehabilitation of sites (following the removal of alien plant species) would sometimes be needed in order to prevent or reduce the soil erosion stimulated by the clearing of plants (Van Wilgen et al., 2002, Milton, Dean and Richardson, 2003).
Location Specific Management InformationAustralia
Biological: Native bud, flower, fruit, and seed-feeding Cecidomyiidae gall midges have been found to occur naturally on A. mearnsii. Aveiro (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Beja (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Braga (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Coimbra (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Evora (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Faro (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Hawaii (United States (USA))
A. mearnsii was listed as a noxious weed in Hawaii and targeted for eradication or control by the Hawaii Department of Agriculture (1992). Leiria (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Lisboa (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Madeira Is. (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Portalegre (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). Setubal (Setúbal) (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99). South Africa
Control involving manual removal or chemical control of weed species is labor intensive, expensive and usually needs to be applied indefinitely (is a short term solution). Sustainable long term solutions might be possible using biological control agents. A broad cost-benefit analysis taking into account the varied benefits and costs associated with A. mearnsii in South Africa concluded the most feasible and relatively cost-efficient management plan would be to combine biological control (using seed-feeding biocontrol agents) with physical control. The study took into consideration the preference of wattle growers for a biological control agent that would not affect vegetative growth of the plant. It also cited the labor intensiveness of the physical removal as an advantage, due to the creation of jobs in a country suffering from high levels of poverty and unemployment (ARC/LNR 1997, Zimmerman and Neser 1999; de Wit, Crookes and van Wilgen, 2001).
Preventative management: Wattle growers are currently testing a range of related Acacia species that are as invasive as A. mearnsii for commercial planting in South Africa; it would make sense to identify the responsibilities of associations benefiting from their release (Dunlop, 1998, de Wit, Crookes and van Wilgen, 2001).
Integrative management: The South African government developed a Working for Water program that aimed to ameliorate the problems caused by Acacia species and other invasive plants. Between 1995 and 2000 over $100 million of poverty-relief funds on the program, which focused on short term solutions and organised the physical and chemical clearing of invasive weed around water courses and water catchments. The program involved more than 30 projects in eight provinces, employed thousands of workers and empowered communities to care for their water and environment. After seven years of implementation of this project it became clear that the rehabilitation of sites (following the removal of alien plant species) would sometimes be needed in order to prevent or reduce the soil erosion stimulated by the clearing of plants (van Wilgen et al. 2002, Milton, Dean and Richardson, 2003; Hill, Gordon and Neser, 1999).
Biological: To date only one species-specific invertebrate has been used as a biological control agent of A. mearnsii; a seed-feeding weevil has been released in areas where the wattle is not grown commercially.
Another insect (a wasp, Bruchophagus acaciae) has been investigated for its use as a control agent for Acacia species. The wasp develops in the pods and feeds on the seeds of some Acacia species. The larvae over winter inside fallen seeds and the adults emerge as the pods reach full size (consequently laying eggs in the seeds of pods). Observations of the wasp in New Zealand (where the Australian-originating species was first described) suggest that the host-range of B. acaciae is restricted to Acacia species of Australian origin (but further investigation is needed). However B. acaciae does not infest the seed pods of A. mearnsii. This is presumably because A. mearnsii flowers in late summer, carries ""protopods"" throughout winter, and produces pods earlier in the following spring than those of Acacia that are susceptible to the wasp. In susceptible species pod formation occurs in synchrony with the appropriate developmental stage of the wasp (Hill, Gordon and Neser, 1999). Viana do Castelo (Portugal)
It is declared as invasive on the Portuguese Exotic Species List (Dec.lei 565/99).
Management Resources/Links
1. Adair, R. J., Neser, S., Kolesik, P. 2000. Australian seed-preventing gall midges (Diptera: Cecidomyiidae) as potential biological control agents for inavsive Acacia spp. on South Africa. Proceedings of the X International Symposium on Biological Control of Weeds. 4-14 July, Montana State University, Bozemann, Montana, USA.
Summary: Information on the effects of A. mearnsii in South Africa and possible biological control agents. 3. Champion, P. D., S. M. Beadel, and T. M. Dugdale. 2001. Turf communities of Lake Whangape and some potential management techniques. Department of Conservation: Wellington, New Zealand. Science for Conservation 186. 4. Daehler, C.C; Denslow, J.S; Ansari, S and Huang-Chi, K., 2004. A Risk-Assessment System for Screening Out Invasive Pest Plants from Hawaii and Other Pacific Islands. Conservation Biology Volume 18 Issue 2 Page 360.
Summary: A study on the use of a screening system to assess proposed plant introductions to Hawaii or other Pacific Islands and to identify high-risk species used in horticulture and forestry which would greatly reduce future pest-plant problems and allow entry of most nonpests. 5. De Wit, M.P., Crookes, D.J. and Van Wilgen, B.W. 2001. Conflicts of Interest in Environmental Management: Estimating the Costs and Benefits of a Tree Invasion, Biological Invasions: 3 167 - 178.
Summary: A good overview of the associated uses and negative impacts of A. mearnsii in South Africa, as well 6. Dye, P. and Jarmain, C. 2004. Water use by Black Wattle (Acacia mearnsii): Implications for the Link Between Removal of Invading Trees and Catchment Streamflow Response, South African Journal of Science: 100 40 - 44.
Summary: A study on the evaporation rates from areas infested with A. mearnsii in Western Cape and KwaZulu-Natal in South Africa. 8. Goodman, P.S. 2003. Assessing Management
Effectiveness and Setting Priorities in Protected Areas in KwaZulu-Natal, BioScience53 (9): 843 - 850.
Summary: The threats to conservation faced in the KwaZulu-Natal province of South Africa. 9. Hill, R.L., Gordon, A.J. and Neser, S. 1999. The Potential Role of Bruchophagus acaciae (Cameron) (Hymenoptern: Eurytomidae) in the Integrated Control of Acacia Species in South Africa. In Spencer, N.R. (ed.) Proceedings of the X International Symposium on Biological Control of Weeds. Montana State University: Montana. 919 - 929.
Summary: The paper discusses the appropriateness of the wasp Bruchophagus acaciae for use as a biological control agent for Australian Acacia species. Results Page: 1
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