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In this paper a new model of short-term price levelling behaviour is introduced, for the case of variability arising from demand-side factors rather than supply-side factors. The key components are the direction of the information flow in the market, and the ability of value chain participants to adjust their demand for and supply of market services. The model is illustrated using data from the Papua New Guinea coffee industry. Almost all PNG coffee is exported to a wide range of countries. The industry has a competitive marketing structure with many active producers and buyers of various sizes. There is keen competition for the limited supply of coffee, but inefficiency in the pricing mechanism has long been a concern to many producers in the industry, in particular the smallholder coffee producers. They argue that increases in world coffee prices have not been fully passed on to growers, with exporters and processors able to hold their buying prices stable in the face of rising world market prices. In this study marketing margin analysis is used to investigate and test hypotheses related to price levelling, and in addition, the influence of marketing costs and throughput, on the aggregate industry margin, and the exporting margin and processing margin components. Average monthly price data over the period January 1999 to December 2010 are used. Using simple regression models, at the whole chain level short -run price levelling is confirmed and both aggregate costs and total volume of exports are significant determinants of the size of the margin. Short-run price levelling is also confirmed at both the exporting and processing stages, but in the preferred models, while throughput is an important determinant of exporter and processing margins, costs have a significant but negative effect on margins. Partial adjustment processes are important in determining margins at all stages. [ABSTRACT FROM AUTHOR]

Food value chain businesses form alliances with horizontal and/or vertical partners to take collective action to either overcome or ameliorate chain failure, or to take advantage of new opportunities available due to innovations in products or processes. The desired outcomes from the collective action would no t be possible to achieve if these businesses acted independently. While such alliances and collaborations may take many forms, depending on the degree of commitment, the kind of governance and infrastructure linkages, they can often be thought of as "clubs" for the purpose of economic analysis. Several different types of clubs can be identified, thus the path to collective action chosen by clubs may vary according to existing capabilities and the scope for collaboration, particularly in relation to the potential for value-creating innovation. The result of the collective action is the provision of a chain good or service, which usually leads to greater and more valuable chain coordination. By collectively identifying, funding and acting to capture positive externalities associated with innovation, businesses in many parts of a food value chain can widen opportunities to increase whole-of-chain surplus as well as private profits. In this paper five mini-case studies are presented to demonstrate the breadth of past collective actions undertaken by businesses in food value chains, two in Europe and three in Australia. These are the Euro Pool System, and Global Standards certification in Europe and globally, as well as Meat Standards Australia, an Australian beef organic producer alliance (OBE Organic®), and the supply of food to households during Covid-19 lockdown in Australia. Each case study yields insights into the rationale of how businesses in different food value chains in different countries have acted as a club to use their joint resources to internalise positive innovation and coordination externalities. [ABSTRACT FROM AUTHOR]

Concerns over livestock production practices have resulted in increased consumer preferences for certified products. Australian beef buyers' survey data revealed the preferences of consumers who would buy differentiated beef based on animal welfare, safety, health, or environmental -friendly considerations. Female respondents are more likely to buy certified animal welfare products. Buyers with children, and those who value branded beef, are more likely to buy products differentiated by a bundle of credence attributes. Given that Australian beef consumers eat similar amounts, there are opportunities for differentiating beef products according to credence attributes and offering them in a range of retailers. [ABSTRACT FROM AUTHOR]

With increasing population and demand for food, reducing food loss and waste is one of the greatest challenges worldwide. Current estimates point to over 1 billion tons of food lost and wasted worldwide, though nearly 10 percent of the global population is suffering from undernourishment and food insecurity. In Mozambique, about one-quarter of the population suffers from undernourishment and food insecurity. Estimates from FAO point to postharvest losses of maize in Mozambique at about 3.69 to 7.92 percent; this is less than one-fifth of the on-farm losses reported by other authors. In this study, an Equilibrium Displacement model is used to assess the economy-wide impact of postharvest losses of maize at the farm level. The impact of a 3 percent postharvest loss is tested. Results suggest that even this very conservative percentage of postharvest losses has a direct annual net cost of around $USD 28 million for both farmers and consumers domestically. This is equivalent to over 1 percent of the national budget. It is also higher than the average cost of food aid programs received over the last three years. Therefore, reducing postharvest losses of maize along with other interventions is crucial to achieve sustainable development and economic growth. [ABSTRACT FROM AUTHOR]

Agriculture in low latitude countries such as Sri Lanka is already operating at the maximum temperature limits for crop growth and faces increased production risk from expected climate change. Sri Lanka is a developing country with limited economic and technological capacity to develop adaptation strategies; hence more vu lnerable to climate change than developed countries. Coconut (Cocos nucifera L) is a rain fed perennial crop important in Sri Lankan culture, food consumption and the economy. It is the second most important food in the Sri Lankan diet after rice. Several studies have examined the impact of climate change on Sri Lankan agriculture, but none were conducted to simulate the impact of future climate change and future adaptation strategies on coconut production, or to calculate the economic welfare effects for different stakeholders in the coconut value chain. In this paper we report the development of an economic model of the coconut value chain that allows prediction of welfare impacts, and a quantitative representation of coconut yield that allows prediction of the impact of changing climatic conditions. The average outcome of 16 climate models was used to generate future climatic conditions, with two future climatic scenarios for 2020, 2030 and 2050 considered for three production regions. The most important yield estimate was a yield decline of more than 10 percent in the wet climatic zone due to the expected increase of maximum temperature. Without extra adaptation measures this is predicted to result in a loss to the industry of 4,795 Rs. Million annually by 2020, which is nearly 4.7 percent of the total value of the industry at equilibrium prices and quantities. The negative impact of climate change has the potential to be reduced with the implementation of additional adaptation practices. However, the cost effectiveness of these practices needs to be considered. Wider adoption of fertilizer application at specific times and moisture conservation practices are estimated to be economically beneficial. [ABSTRACT FROM AUTHOR]

There was a flawed policy banning Glyphosate in Sri Lanka in 2015 that was later withdrawn, but only after significant economic losses were experienced, especially in the tea industry. The focus of this study is to highlight the impact of the policy on the tea growing sector and determine the economic cost on the tea value chain. It is also aimed to remind policymakers that science and economics, theory and evidence, still matter in implementing public policies. The methods used in the study involved gross margin budget analysis of tea grower groups, thematic analysis of qualitative data collected through interviews and welfare analysis of the impacts of the ban on the industry using an Equilibrium Displacement Model. Direct impacts were experienced by the farm sector engaging in tea cultivation. An unintended consequence of this policy was rejection of tea exports from Sri Lanka to Japanese markets. The annual loss in the tea industry by banning Glyphosate was estimated to be LKR 20 billion (more than $US100 million), though the true cost likely was much more than this. Hence, policies introduced to minimize adverse impacts from market failures warrant full attention being given to the scientific, economic, social and political realities of the case at hand, and the likely consequences for the affected parties and their responses. [ABSTRACT FROM AUTHOR]

Certain members of a population consciously and deliberately decide to take joint action to provide particular types of goods or services that are at least partly excludable and at least partly congestible because it is too costly to provide such goods individually. These goods are called club goods or collective goods. We first define some key concepts in club theory and public choice. This includes the prospects for determining the optimal level of membership of a club, how to determine the optimal level and range of provision of services by a club, and consideration of the dynamics of club membership. Then we examine the ways in which club theory can help provide an alternative approach to recognising and overcoming market failure in agricultural and food value chains. We note that useful insights can be gained by considering value chains as 'latent clubs'. That is, they are systems that exist which are either inactive or have not been fully developed, but which have the potential for improvement through collective action. If value chain members do exploit an opportunity to reap the rewards of collective action, then forming a club that comprises the whole chain or a subset of chain members offers an efficient organisation design to do so. We find that all of the calculus that has been identified for clubs can be applied to agricultural and food value chains. However, there are two particular issues that require further consideration. One is the nature of risk in agricultural value chains, and how it is related to member preferences, and the other is the form of collective action to be taken by agricultural value chains in the future. [ABSTRACT FROM AUTHOR]

Strategic fit is the nature of the link between the customer priorities that a value chain hopes to satisfy, and the capabilities that are available in the value chain to implement that objective. Usually, there is a trade-off between value chains that focus on being responsive to customer needs and those that focus on supplying at the lowest possible cost. If demand uncertainty is low, a low-cost value chain is the best strategic fit; conversely if demand uncertainty is high, a responsive value chain is the best fit. A poor fit means lower chain surplus to be shared among the chain participants. We provide an outline of an analytical framework for determining the optimal level of responsiveness for a food value chain. We then present and discuss two case studies. Both feature initiatives aimed at internalising positive chain externalities and capturing chain goods within the Australian beef value chain. We use our framework to show how these initiatives are predicted to promote responsiveness and thus achieve a better strategic fit and higher surplus for the whole chain. Verifying that such a move would indeed contribute to higher chain surplus would require some new measurements of whole-of-chain outcomes so that the economic relationships making up the framework could be estimated and analysed. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to explore opportunities to improve cashew value chain performance in Mozambique in ways that create income for smallholders and small and large scale processors. Considering the importance of the cashew industry for the national economy and for poverty reduction, the suggested improvements can be used by policy makers, investors, and donors to re-examine policy strategies, resource reallocation and the development of infrastructure. It may also trigger the interest of the private sector to develop new marketing strategies. The paper commences by giving the background to the cashew industry and its impact on rural development, followed by policy interventions and major activities. Then, a SWOT analysis, value chain mapping, strategic fit and drivers of profit are outlined. The Sunshine Nut company is presented as an example of an innovative business model in the cashew Industry. It is concluded that investment in market research, domestic value adding and balancing customer requirements may potentially enhance competitiveness and efficiency in the cashew value chain in Mozambique. [ABSTRACT FROM AUTHOR]

The concept of value chain upgrading and promotion has been proposed as a vehicle for small -holder farmers in developing countries to gain access to higher value markets and thus generate greater income for their families and communities. However, there are many instances where investments in upgrading have not generated the expected outcomes. One of the contributing factors has been that existing approaches focus more on who does what rather than the real problem to be addressed. A chain failure framework on the other hand focuses attention on the core problem and the appropriate response, rather than on who does what. It takes a system view rather than a function or component view, and it starts from the supposition that the only reason for intervening in a value chain is to increase chain surplus, where chain surplus is properly measured to include any chain or social externalities. In this paper we review some of the existing literature on value chain upgrading and promotion as proposed for developing country situations, outline the essential elements of the chain failure/chain good theory and its relationship to the club goods literature, and then assess whether the chain upgrading and promotion literature can be reconfigured as a chain failure/chain good problem, using a number of published case studies. Finally, we discuss various types of governance models used in agricultural value chains in developing countries and suggest how well they might align with the chain failure/chain good approach. [ABSTRACT FROM AUTHOR]

Useful insights about the operations of value chains can be gained by considering them as “latent clubs”, that is, systems having the potential for improvement through collective action. Club theory therefore can be applied to examine ways to increase the economic surplus of a food value chain by participants taking collective action within a club good framework. The results of such action are called “chain goods”. If these types of goods are not supplied along the value chain, value chain partners cannot maximise whole-of-chain profit. The result is “chain failure”; a concept analogous to the market failure of public goods in the wider economy. If an opportunity exists for partners in a value chain to collectively provide such goods, forming a club may be an efficient way do so. Horizontal and vertical strategic alliances are formed among firms, or groups of firms, in the value chain at the same level and/or across different levels. These alliances within a value chain are formed to correct some particular chain failure(s), such as supplying chain goods or internalising chain externalities. Strategic alliances may comprise all or only some chain members. Thus, they are clubs. The theoretical concepts of chain failure, chain goods and chain externalities can be used as a framework for evaluating whether to invest or not in a strategic alliance. The fact that there are existing alliances which appear to be organised in this way suggests that these concepts have practical as well as theoretical merit. [ABSTRACT FROM AUTHOR]

The nitrogen (N) fertilizer used to help grow fully irrigated cotton in Australia adds, through several pathways, nitrous oxide (N2O) to the stock of nitrous oxide in the atmosphere and increases the global externality cost of the warming climate. The focus of this analysis is on the extra social benefits and the extra private costs and negative externality costs of using different quantities of N on land in NSW and QLD to grow cotton over a year, and over the coming 15 years, as compared with not growing cotton on that land and replacing the activity with another economic activity. Starting at the farm, a welfare economics framework including the concepts of response of crop yield to N fertiliser, private costs, externality costs, marginality, with-without counterfactuals, opportunity costs, crop rotations, discounting, probabilities, consumer surplus, producer surplus and net social benefit are used to estimate the size of the social benefits and costs of N used to grow irrigated cotton. In the case analysed, with an illustrative counterfactual, the externality cost of direct N2O emissions from growing cotton after counting for the counterfactual was $102/ha yielding a Benefit to Cost (B:C) ratio of 7.2:1. The net social benefit on the industry over 15 years at a 5 per cent real discount rate per annum in net present value terms was $5.6 billion with an annuity of $541 million. In the case analysed and with the probabilities assumed for the values that the key uncertain variables could take, with only direct N2O emissions counted as the negative externality of the N used, there would be a 90 per cent probability that the B:C ratio of N used to grow cotton was between 5.4:1 and 9.6:1. There would be 55 per cent chance the B:C ratio would be more than 7:1. There would be zero chance the B:C ratio would be under 4:1. A significant finding about the negative externality of the N2O emissions from the N applied to cotton was that $80 of the $116/ha externality cost from the N2O emissions came from the marginal 50 kg of N/ha that was used. If the response function is relatively flat around the typical level of N/ha that is used in a typical year, then the marginal units of N applied would be adding little extra cotton yield relative to the extra externality cost attributable to the N2O emissions. In this situation, there would be scope for small reductions in N/ha used to grow extra cotton to bring large reductions in the externality cost of the N2O emissions from N used to grow cotton. [ABSTRACT FROM AUTHOR]

Abstract: Australian beef consumers have different preferences given their characteristics and the effect on expected quality of cues related to health, production process and eating experience. Beef brands using Meat Standards Australia (MSA) grades can help to signal quality and reduce consumers'' uncertainty when shopping. The objective of this study is to identify the characteristics of beef buyers and their perceptions about product attributes that affect the propensity to buy branded beef. Binary logistic models were applied identifying differences between all respondents and the potential target market, including buyers in medium to high income segments, and between buyers in the target market who would buy branded beef for taste and health reasons. Variables increasing the propensity to buy branded beef include previous experience, appreciation for branded cuts and concern about quality more than size. Finally, variations in preferences for marbling and cut were found between buyers who would buy branded beef for taste and health reasons. [Copyright &y& Elsevier]

Abstract: The control of weeds provides agricultural, environmental and social benefits. The agricultural gains typically dominate, and many studies have estimated these values. The environmental gains rest on the protection of plant communities from weed invasions, but these benefits have proved hard to value due to the lack of data from relevant market transactions. An estimate of these gains is now derived from a set of Australia-wide costs to control 35 major weeds affecting the agricultural and forestry industries. Control costs varied closely with the number of threatened special conservation areas, and with the number of threatened plant species, within the distribution of the weeds. Across all agricultural weeds, control costs increased by about $5800 per year for each additional threatened special conservation area, and across all forest weeds, control costs increased by about $800 per year for each additional threatened special conservation area. Across all agricultural and forest weeds, control costs increased by at least $65,000 per year for each additional threatened plant species. Following standard economic assumptions about market transactions, these estimates can be taken as the values of the annual environmental benefits to the community from protecting an extra special conservation area or an extra species – given the budgets available to the weeds managers. These environmental gains alone appear to cover a substantial proportion of the control costs. The marginal estimates of value are extended to cases where many further areas are protected, by introducing certain assumptions about the change in marginal utility, and by using ecological information to help choose between these assumptions. The application and qualifications of the values are discussed. [Copyright &y& Elsevier]

Food loss and waste are of global concern. In developing countries like Mozambique, it seems to be a major issue at the upstream end of supply chains, which is also regarded as postharvest losses (PHL). In this study, PHL is analysed in the context of maize in Mozambique, which is the most important crop in that country. The analysis focuses on empirically testing a simulation modelling approach for determining the short and mid-run economic impacts of PHL. A system dynamics model is applied. This model acknowledges climate, management, and domestic and regional marketing related factors as major drivers of PHL. A novel result from this study suggests climate related factors as the cause of a systematic amount of PHL at about 70,000 tons per year. However, marketing forces also play an important role to explain the overall PHL, particularly in periods domestic production increases sharply. The impact of potential interventions in the value chain are also tested. [ABSTRACT FROM AUTHOR]

Context. This study assesses the monetary value of product quality information, specifically feedback from slaughter and production methods, within the Australian beef and sheep meat supply chains. Aims. The primary objective was to investigate the value assigned by supply chain actors to product quality information, measured as willingness to pay for receiving it or willingness to accept payment for providing it. The study also aimed to explore how the value of this information varies based on information quality and quantity. Methods. A contingent valuation approach was employed, utilising survey data from 104 producers. Logit models were used to identify the factors influencing meat producers' willingness to accept payment and willingness to pay. Key results. Over one-third of cattle and sheep producers expressed interest in receiving feedback from slaughter information and providing production methods information. Production methods information had the highest mean value at the premium information quality and quantity level, with values of AU$20.49/head in the beef industry and AU$10.13/head in the sheep industry. Conversely, feedback from slaughter information had the lowest mean value at the low information quality and quantity level, with values of AU$0.83/carcass in beef and AU$0.14/carcass in sheep. Farmers' experience and education level significantly influenced their willingness to accept payment and willingness to pay for product quality information. Conclusions. A significant proportion of producers within the Australian beef and sheep meat supply chains express a desire to provide or pay for product quality information. The value assigned to this information demonstrates a positive relationship with higher information quality and quantity. However, variations in expressed value of different information types, and the influence of farmer and farm characteristics, suggest the presence of chain failures that disrupt information valuation. Implications. These findings have important implications for improving the performance of the red meat supply chains. Understanding the factors that influence the valuation of product quality information allows stakeholders to develop targeted strategies to enhance the efficiency and effectiveness of information exchange. This may involve addressing chain failures, and implementing measures to ensure consistent and accurate valuation of information. Ultimately, these improvements can contribute to enhanced decisionmaking processes and overall supply chain performance in the Australian beef and sheep meat industry. [ABSTRACT FROM AUTHOR]

The Australian Centre for Agricultural Health and Safety established a longitudinal study of 335 NSW farm enterprises to derive data on farm health and safety management and how it relates to farmer perceptions. The analysis reported in this paper benchmarked the perceptions of the study informants on the role and importance of health and safety on their farms and reviewed the safety performance of the study enterprises, focusing on management of safety systems and processes and control of major risks and hazards on their farms. The results not only challenged some apparent misconceptions, such as older farmers having more negative attitudes towards farm safety than younger farmers, but it also identified industries from within the study population that are performing well in the management of safety and the possible reasons behind their success. Importantly, it also observed an area of disconnect between having a positive attitude towards farm safety and its role and importance, and actually implementing farm safety systems and management processes on the farm. These findings provide evidence for the possible benefits of tailoring farm initiatives and interventions based on gender, age and industry. Set beside other analyses of the changes farmers had made on their farms, the prompts and drivers for making those changes, and the issues and risks that the farmers see as important on their own farms, a wealth of information is available to health and safety researchers, Farmsafe Australia, work safety authorities and industry bodies to direct and prioritise their research programs and policy initiatives. [ABSTRACT FROM AUTHOR]

Consumers of fresh pork have long been aware of the risk of their pork purchases not meeting eating expectations due to unpleasant taste or smell or other unsatisfactory quality characteristics such as a lack of tenderness. Boar taint, or the risk of it, is one of the most important factors identified in surveys of consumers of pork as being responsible for having a poor eating experience. Immuno-castration (IC) of entire male pigs is one method of reducing boar taint in pork. Currently about 60 per cent of male pork produced in Australia is immune-castrated. The question asked here is whether it would be profitable for the industry if the remaining male slaughter pigs were immuno-castrated as well. The additional costs associated with IC include the costs of the vaccine, extra labour costs, and additional costs arising from abscesses at the injection site causing increased product downgrades and stoppages of the slaughter line for cleaning. A major benefit of IC for the pig industry is a reduction in consumers of pork enduring poor experiences from unpleasant taste or smell when they eat pork. Over time, reducing the occurrence, and the risk of occurrence, of having a less than satisfactory experience when consuming pork has the potential benefit of the industry avoiding losing customers, and even increasing demand for pork, above what it would be with the continuation of the current proportion of boar-tainted pork in the total national supply of pork. Over the next ten years, if national consumption of pork increases at the same trend of the past decade, the benefits from avoided annual losses of demand or from increases in demand by just 0.5 per cent of total annual national consumption of pork would cover the cost of the remainder of the industry adopting IC. This conclusion applies if IC was adopted fully and immediately and the cost was the lower of the range of possible cost estimates at $0.10/kg carcass weight. More realistically, if producers adopted IC more slowly and adoption of IC took five years, and the cost of using IC was $0.10/kg carcass weight, then avoiding or preventing a loss of 1.5 per cent in annual sales would mean the total benefits exceed the total costs of achieving this outcome. Such relatively small gains in sales or avoided losses of sales seem eminently achievable. The conclusion of the BCA is that an increased use of immuno-castration in Australia's pig production system that reduces the prevalence and the risk of boar taint would have a high likelihood of delivering a net benefit to participants in the industry. [ABSTRACT FROM AUTHOR]

A subset of data from a broader, longitudinal study of 335 farm enterprises throughout New South Wales, Australia, was examined focusing on the changes farmers were making to farm health and safety and the motivating drivers behind those changes. The most frequently reported changes to health and safety by participating farm enterprises were shearing shed safety improvements, improved chemical safety and handling, purchasing new equipment or upgrading existing equipment, greater provision and access to personal protective equipment and improving safety of stockyards and procedures. When the drivers behind the changes to farm practice were assessed, occupational health and safety requirements or legislation were the most frequently reported by participating farm enterprises, followed by increased safety awareness or consciousness, a general desire to improve safety and standards on their farm, the realisation or identification of a risk or hazard and to gain improved efficiency or cost savings. The research has questioned some preconceived ideas relating to farmers' perceptions, attitudes and practices in relation to farm safety and has identified potential new approaches for increasing adoption and implementation of farm safety recommendations. [ABSTRACT FROM AUTHOR]

A subset of data from a larger survey of 335 farm enterprises throughout New South Wales was examined, focusing specifically on farmers' perceptions about major hazards on Australian farms. The data collected from participating enterprises clearly demonstrate that there is a disconnect between what farmers perceive as the risks on their farm and what hazards and risks cause the highest rates of fatalities in Australian agriculture. For example, previous research has shown that tractors were the most commonly reported agent of death by injury on Australian farms over the period 2001-04, accounting for 19 per cent of fatalities, followed by all-terrain-vehicles (ATVs). However, a frequency analysis of identified risks or hazards by study participants, rated tractors at 20th, with ATVs even further down the list at 27th; just 11 of the 335 enterprises rated ATVs as a risk on their farms. The most frequently reported injury agent by study participants was livestock handling and stockyards, followed by silos and chemical handling. While these agents are seen commonly in farm safety campaigns and promotions due to the legislative requirements with training and operation, with the exception of livestock handling, they do not feature highly in injury hospitalisation, and none of these agents feature in the causation of deaths on farms. [ABSTRACT FROM AUTHOR]

The article discusses the DNA testing service for beef cattle by the U.S. Department of Agriculture (USDA). Explored are topics on genomics research for beef cattle, phenotype prediction and investments in genomic research. Also tackled are concepts of Expected Progeny Difference (EPD) and Genomics Information.

Environmental weeds are plants that invade natural ecosystems and present a serious threat to conservation of nature. Environmental weeds have been implicated in the extinction of several indigenous plant species, and they also threaten ecosystem stability and functional complexity. Historically, emphasis in weed control in Australian national parks has been placed on chemicals, manual pulling of small plants, excluding tourists and feral animal control measures. Recently, biological control has been introduced to control weed infestations. These methods typically have been applied as funds have become available, with little opportunity to consider their long-term effectiveness. As the threat from environmental weeds is becoming more fully recognised, an integrated, strategic, ecological and economic approach to weed management is needed. A deterministic dynamic programming model is developed for this purpose in this paper. A case study for scotch broom is presented, to assess the ways in which this approach can address the policy issues that face the community in the management of an environmental weed in a national park. The model takes account of the weed population dynamics, the effectiveness and cost of control measures, and the value of the park outputs (biodiversity, recreation and grazing). The dynamic programming model includes weed density and seed bank as state variables and a budget constraint for the control variables. The model is used to derive optimal control rules for any given state of the weed population. An optimal decision rule provides a package of control measures that can be used to attack the problem each year, depending on the current weed density and seed bank. Optimal trajectories are developed for a planning horizon of 45 years, and the effect of the budget constraint is analysed. The marginal value of an extra dollar for weed control, in terms of discounted future benefits, is estimated. It is shown that a combination of controls that targets both weed density and the seed bank is important. It is also shown (given the assumed parameters) that biological control is worth undertaking, as it appears as part of most of the optimal strategies identified. The paper concludes with policy recommendations for managing weeds in natural ecosystems. [Copyright &y& Elsevier]