Strategies employed to control L. flava should emphasis public education. The effects of the invasive weed should be outlined, and the practices necessary for limiting its spread should be made clear. For example, plants should be uprooted and burnt (or deep-buried) to prevent them from re-establishing and the plants should be (preferably) removed before the weed flowers and sheds its seeds. An increased understanding of the life cycle of the weed should be attempted through ecological studies; these may highlight the most vulnerable stages of the life cycle and eventually lead to more effective control measures. The use of the plant as a leafy vegetable, green manure, medicine, or in other applications should be documented so that the social and economic factors contributing to the spread of the plant can be addressed (and potentially reduced).
Preventative measures: In general, early detection of any invasive weed species provides the best opportunity for intervention. This is because eradication or control programs implimented at an early stage of an invasion have a higher chance of success and are more cost-efficient. To encourage early detection, the Northern Australian Quarantine Strategy (NAQS - a sub-program of the Australian Quarantine and Inspection Service) have undertaken a survey of the distribution of known weeds (and the occurance of new weeds) in northern Australia. Field surveys such as this provide current distribution records of weeds in an area and are necessary for fast detection of a new invasive weed. Detection is also hindered by the under-representation of weeds in herbaria (collections of preserved plants). This is due to the fact that botanical collectors rarely document introduced species. To address this, botanists working under the NAQS collect naturalised species in addition to native taxa, providing an opportunity to consolidate knowledge of weed flora in the region (considered to be essential for prioritising weed management in any area) (Waterhouse, 2003).
Location Specific Management Information
In 1995 it was estimated that L. flava with a high level of resistance to 2,4-D (a synthetic auxin) infests 51 to 100 sites (covering 1,001 to 10,000 acres) in the Simalungun and Deliserdang Counties in Sumatra (Indonesia). The area infested is believed to be expanding (Purba, 2003).
The following management strategies have been suggested for control of L. flava: (1) Survey the dominance and growth of L. flava under different geographical locations (low land, midland and highland) (2) Study the effect of different environmental factors on weed infestation and distribution (3) Use geographical information systems to assess the pattern of spread of L. flava for ecosystem modelling (4) Determine the influence of the weed on biodiversity and vector borne diseases (5) Evaluate the control measures under different growing conditions using an eco-physiological approach (6) Identify the biotypes of L. flava in affected areas and prepare distribution maps (7) Identify antagonistic organisms and study their relationship with the weed to best determine their potential use as a biological control agent (including an evaluation of control effectiveness).
In 1977 at Perai substation of Malaysian Agricultural Rice Research and Developmental Institute it was observed that L. flava was resistant to 2,4-D and bensulfuron-methyl (a sulfonylurea herbicide), which belong to the ALS inhibitor and synthetic auxin herbicide groups, respectively (Abhilash, P.C., pers. comm., 2004; Azmi, 2003). In 1998 it was estimated that multiple resistant L. flava infests two to five sites (covering 11 to 50 acres) in the Seberang Perai and Seberang Perak rice areas (Azmi, 2003). Reports have been made that the density of rice seedlings affects the growth of the weed, suggsting that an adequate density of rice seedlings can be effective means of control for this herbicide resistant weed.
Papua (Irian Jaya)
Botanists or weed scientists from collaborating organisations in Indonesian (in the province of Papua) participate in NAQS surveys. Although the surveys are relatively brief and infrequent (and are unlikely to identify every new weed that has arrived), hopefully they will help draw attention to some of the major and emerging weed problems in the region.
Papua New Guinea
Botanists or weed scientists from collaborating organisations in Papua New Guinea participate in NAQS surveys. These survey activities are confined to the western border region of Western and Sandaun Provinces, and the coastal fringe adjacent to the Torres Strait islands. Although the surveys are relatively brief and infrequent (and are unlikely to identify every new weed that has arrived), hopefully they will help draw attention to some of the major and emerging weed problems in the region.
Infestations of L. flava are the target of an eradication campaign in north Queensland. Plants are removed by hand and destroyed by deep-burial. Infested sites will be regularly inspected to detect and remove new seedlings. Weed surveys have been conducted by the Northern Australia Quarantine Strategy (NAQS - a sub-program of the Australian Quarantine and Inspection Service) to document the distribution of weed flora in northern Australia, Papua New Guinea, and the Province of Papua (Indonesia). The primary objective of the surveys is to detect new threats before they become well established, thus enabling implementation of preventative strategies with a relatively low cost and high probability of success. To supplement survey activities, state and local government weeds officers and the general public are encouraged to submit weed specimens for identification by the NAQS botanists.
1. Abhilash, P.C, 2004. School of Environmental Sciences, Mahatma Gandhi University, Kottayam, Kerala, India.
Summary: Personal communication: notes from study undertaken at School of Environmental Sciences, Mahatma Gandhi University, Kerala India.
3. Ogle, B.M., Anh Dao, H.T., Mulokozi, G. and Hambraeus, L. 2001. Micronutrient composition and nutritional importance of gathered vegetables in Vietnam, International Journal of Food Sciences and Nutrition 52(6): 485 - 499.
Summary: A study on the nutrient composition and nutritional contribution of naturally occurring vegetables in four villages in Vietnam.
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