Some risks in the agricultural sector are unavoidable while others can be managed. Agrometeorological risks in the farming sector include the temporal and spatial variability of rainfall, temperature, evaporation and, in climate change scenarios, atmospheric carbon dioxide levels. While such factors may impact directly on plant growth and development they can also exert an important indirect effect by influencing the life cycles of plant diseases and pests. In addition they may have a profound influence on attempts to control such pests, as is seen when an unexpected rainfall event causes dilution or early hydrolysis of a surface pesticide, or when hail damage opens the way for mould, bacterial or insect attack. Integrated pest management (IPM) must take into account such risks if crop damage is to be minimized, tte implications of agrometeorological risk studies in countries such as Australia offer not only local perspectives on IPM but also provide information for improved crop profitability, natural resource usage and agricultural sustain-ability in other countries, where a critical relationship between crop success, regional food security and human survival may exist.
tte capacity of an individual farming enterprise to carry out IPM depends largely on its given financial and economic situation. A business with a high level of debt may only have capacity for low cost management options, such as the planting of disease-resistant varieties and routine pre-crop disease control, while a business that is leveraging and expanding its asset base maybe able to cope with higher cost management options, such as the introduction of new crops or rotation of crops to preserve the long-term status of the land (Lloyd Kingham, NSW DPI, personal communication, 2006). Given these differences in ability to cope, perception of risk mayvary considerably with level, type and location of enterprise.
Global climate change will inevitably present a challenge to those engaged in agroclimatic risk modeling in the interests oflPM. Agribusiness units most at risk are likely to be those already stressed as a result of factors such as land degradation, salinization and ecological change. Local economic setting must also be taken into account when estimating possible impacts. In countries with a low level of agricultural industrialization, many units maybe based on low capital investment resulting in short-term land use policies, while in industrialized countries units may exist at the other extreme, having over-capitalized on items such as dedicated irrigation systems, slow-growing cultivars and on-site processing facilities. Units at both ends of this capitalization spectrum may, however, be economically marginal in terms of climate change, with increased reliance on state subsidy, off-farm income, or secondary industry support. Such situations do not offer much leeway for farming sustainability through IPM in areas where climate change maybe accompanied by increased disease occurrence or pest invasion.
One way to cope with risk has traditionally been through the use of insurance, although agricultural economists are becoming increasingly skeptical about insurance as a regionally-sustainable risk management strategy. Some crop insurance, however, may enable an enhanced ability to apply IPM in special situations. For example, an agrometeorological risk that can be insured against in Australia is hail. Hail can cause wound sites which allow pathogens to breach external defenses and gain access to plant tissues, resulting in exacerbation of initially superficial damage. In such cases insurance indirectly allows for a measure of protection against microorganic degradation and pest damage. Only farmers in a stable or growing financial situation may, however, be able to afford this luxury (Lloyd Kingham, NSW DPI, personal communication, 2006).
Australian crops of wheat and canola have a local advantage in that the full potential spectrum of destructive pathogens has not yet been established through assiduous quarantine control and an integrated agricultural management system. In some cases, pathogens found in Australia offer less virulent or aggressive forms than those found elsewhere. Pathogenicity generally relies on a subtle interplay between genetics and external biotic and abiotic factors operating within local ecosystems. Abiotic factors may include farming practice, soil differences, seasonal characteristics or climatic conditions.
tte expenditure on integrated control is supported by studies which show that when incursion of an exotic pest occurs or a new variety evolves locally, the result is considerable loss to the industries concerned, with reduction of both quantity and quality of a crop. Furthermore, there is an indirect cost associated with environmental damage resulting from the need to apply additional pesticide (White 1983; Zadoks and Schein 1979). Where epidemic threats are anticipated, contingency planning can enable the use of proactive or less extreme intervention, resulting in reduced pest damage, pesticide use, and ecological impact (Murray and Brennan 2001).
Two climate-sensitive diseases of Australian field crops are stripe rust of wheat and Sclerotinia rot of canola, both having a high risk-ranking in the list of Australian crop diseases (Murray and Brennan 2001). Stripe rust of wheat is estimated to cause on average a loss of about USS 142 million per annum (Brennan and Murray 1998), while stem rot has been reported as causing losses up to USS 37 million, (Hind-Lanoiselet 2006).
In terms of the gross economic production value, wheat is the most important crop in Australia, attracting a large share of public funds for research and development. A substantial part of those funds is raised from production levies that are matched by government funds then disbursed by bodies such as the Grains Research and Development Corporation (Brennan and Murray 1998). Research carried out in terms of this and other funding has already identified the importance of agrometeorological risk assessment (Huda et al. 2004; Wallace and Huda 2005).
ttis chapter discusses some of the Australian research into climate sensitive diseases, in particular wheat and canola, to present some thoughts on the approaches needed for coping with the risks and uncertainties associated with IPM. A perspective on future considerations in this area is also given.
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