Physical: Control techniques of fire and physical removal (cutting) in conjunction with flooding are most appropriate. Motivans and Apfelbaum (1987) suggest that draining techniques used in wetlands can inhibit growth. If the wetland can be drained and then burned during summer, typha will not be able to survive with no water over winter. There have however been no controlled experiments carried out to demonstrate this method. Deep flooding can also cause declines in infestations.
An effective control of Typha can be achieved by a combination of hand or mechanical cutting of stems followed by submergence of the remaining stems. Best results have been achieved by two clippings followed by submergence to at least 7.5cm or 3inches. typha are not shade tolerant, shading using black polyethylene tarps has been tried for killing growth. Degradation of the polyethylene tarps and problems of holding them down are some problems.
Manual removal works best for small seedlings. They are easy to pull out in damp soil, care must be taken to see that all rhizome bits are removed otherwise the plants can reestablish itself (DPIWE, 2005).
Mechanical: Mechanical removal of rhizomes is difficult because of their depth and volumn, however it can be used to reduce size of infestations and by following up with manual removal. The advantages of mechanical and manual removal are that no herbicide is used in water. Care should also be taken to ensure that the excavated material is taken away from the site and killed (DPIWE, 2005).
Exposure of rhizomes to frost by cultivation of the site is a good method when water levels are low (DPIWE, 2005).
Chemical: Treating typha when flowering using herbicides has been found to cause the greatest stress. The disadvantage however of using herbicides is the large volumn of decaying matter that remains which can cause water to go foul and unusable (DPIEW, 2005). Wick and spray applications of Roundup followed by with follow-up treatements has been found to be effective.
Treatment with herbicides like Dalpan followed up by respraying growing tips and making sure that the stems are submerged has been found to be successful. For more details of chemical control please see Motivans and Apfelbaum, 1987.
For more option is herbicide treatment please see Chemical control (DPIWE, 2005).
Location Specific Management Information
Manual, mechanical and chemical options for the management and control of T. latifoliacan be seen at Integrated management options (DPIWE, 2005)
T. latifolia is included in the First Schedule of the National Pest Plant Accord. All plants on the list are designated as Unwanted Organisms, and are banned from sale, propagation and distribution throughout New
Zealand. Please see National Pest Plant Accord for the complete list. Champion and Clayton (2001) Aquatic Plant Weed Risk Assessment Model classifies T. latifolia as a high risk species in New Zealand. It is classified as NZn, An (species, or genus rejected by MAF pre-entry weed risk assessment, or Nichol (1997); species, or genus rejected by AQIS pre-entry weed risk assessment model). It is not naturalised in New Zealand (Champion and Clayton, 2000) but is listed as present within the nursery/aquarium trade (Champion and Clayton, 2001).
4. Champion, P.D.; Clayton, J.S. 2001. Border control for potential aquatic weeds. Stage 2. Weed risk assessment. Science for Conservation 185. 30 p.
Summary: This report is the second stage in the development of a Border Control Programme for aquatic plants that have the potential to become ecological weeds in New Zealand. Importers and traders in aquatic plants were surveyed to identify the plant species known or likely to be present in New Zealand. The Aquatic Plant Weed Risk Assessment Model was used to help assess the level of risk posed by these species. The report presents evidence of the various entry pathways and considers the impact that new invasive aquatic weed species may have on vulnerable native aquatic species and communities.
Available from: http://www.doc.govt.nz/upload/documents/science-and-technical/SFC185.pdf [Accessed 13 June 2007]
6. National Pest Plant Accord, 2001. Biosecurity New Zealand.
Summary: The National Pest Plant Accord is a cooperative agreement between regional councils and government departments with biosecurity responsibilities. Under the accord, regional councils will undertake surveillance to prevent the commercial sale and/or distribution of an agreed list of pest plants.
Available from: http://www.biosecurity.govt.nz/pests-diseases/plants/accord.htm [Accessed 11 August 2005]
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