BSPP Presidential Meeting 2002

Plant Pathology and Global Food Security



Jules Pretty, Centre for Environment and Society and Department of Biological Sciences, University of Essex, UK

The Scale of the Problem

Over the past 40 years, per capita world food production has grown by 25%, with average cereal yields rising from 1.2 t ha-1 to 2.52 t ha-1 in developing countries (1.71 t ha-1 on rainfed lands and 3.82 t ha-1 on irrigated lands), and total cereal production up from 420 to 1176 million tonnes per year. Yet despite such advances in productivity, the world still faces a persistent food security challenge. There are an estimated 790 million people hungry and lacking adequate access to food. The global population of 6 billion people is expected to grow to 7.5 billion by 2020, and then to 8.9 billion by 2050.

During the period to 2020, the urban population in developing countries is expected to double to 3.4 billion, whilst the rural population will only grow by 300 million to 3 billion. Thus the numbers of urban people will, for the first time, have exceeded those in rural areas. Such a change has an important effect on food consumption. As rural people move to urban areas, and as urban peoples disposable incomes increase, so they tend to go through a nutritional shift - particularly from rice to wheat, from coarse grains to wheat and rice, and towards more livestock products, processed foods, fruit and vegetables.

It is clear that adequate and appropriate food supply is a necessary condition for eliminating hunger. But increased food supply does not automatically mean increased food security for all. What is important is who produces the food, who has access to the technology and knowledge to produce it, and who has the purchasing power to acquire it. The conventional wisdom is that, in order to double food supply, redoubled efforts are needed to industrialise agriculture. Though this has been successful in the past, there are doubts about the capacity of such systems to produce the food where the poor and hungry people live. They need low-cost and readily-available technologies and practices to increase food production. A further challenge is that this needs to happen without further damage to an environment increasing harmed by existing agricultural practices.

How Can Agricultural Sustainability Help?

A more sustainable agriculture seeks to make the best use of natures goods and services as functional inputs. It does this by integrating regenerative processes (such as nutrient cycling, nitrogen fixation, soil regeneration and natural enemies of pests) into food production processes. It minimises the use of inputs that damage the environment or harm human health. It builds on farmers knowledge and skills, and seeks to make productive use of social capital, namely peoples capacities for collective action for pest, watershed, irrigation, and forest management.

Agricultural systems emphasising these principles are also multi-functional within landscapes and economies. They jointly produce food and other goods for farm families and markets, but also contribute to a range of valued public goods, such as clean water, wildlife, carbon sequestration in soils, flood protection, groundwater recharge, and landscape amenity value. As a more sustainable agriculture seeks to make the best use of natures goods and services, so technologies and practices must be locally-adapted. They are most likely to emerge from new configurations of social capital, comprising relations of trust embodied in new social organisations, and new horizontal and vertical partnerships between institutions, and human capital comprising leadership, ingenuity, management skills, and capacity to innovate. Agricultural systems with high levels of social and human assets are more able to innovate in the face of uncertainty

Sustainable agriculture relies more on agro-ecological and organic approaches to food production. This is not to say that modern agriculture cannot successfully increase food production. Any farmer or agricultural system with access to sufficient inputs, knowledge and skills, can produce large amounts of food. But most farmers in developing countries are not in such a position. The central questions today are i) to what extent can farmers improve food production with cheap, low-cost, locally-available technologies and inputs, and ii) to what extent can they do this without causing environmental damage.

The success of modern agriculture in recent decades has often masked significant externalities (actions that affect the welfare of or opportunities available to an individual or group without direct payment or compensation), which affect both ecosystem services and human health, as well as agriculture itself. Environmental and health problems associated with agriculture have been increasingly well-documented, but it is only recently that the scale of some of these costs has come to be appreciated.

Recent Evidence

The University of Essex recently completed an audit of progress towards agricultural sustainability in 52 developing countries. Substantial improvements in food production are occurring through one or more of four mechanisms:

intensification of a single component of the farm system such as homegarden intensification with vegetables and trees, vegetables on rice bunds, or a dairy cow;

addition of a new productive element to a farm system, such as fish in paddy rice or agroforestry, which provide a boost to total farm food production and/or income, but which do not necessarily affect cereal productivity;

better use of natural capital to increase total farm production, especially water (by water harvesting and irrigation scheduling), and land (by reclamation of degraded land), so leading to additional new dryland crops and/or increased supply of water for irrigated crops;

improvements in per hectare yields of staples through introduction of new regenerative elements into farm systems (e.g. legumes, integrated pest management) and/or locally-appropriate crop varieties and animal breeds.

Thus a successful sustainable agriculture project may be substantially improving domestic food consumption through homegardens or fish in rice fields, or better water management, without necessarily affecting the per hectare yields of cereals. The dataset contains details of 89 projects (139 entries of crop x projects combinations) with reliable data on per hectare yield changes with mechanism iv. These illustrate that agricultural sustainability has led to an average per project 93% increase in per hectare food production. The weighted average increases across these projects were 37% per farm and 48% per hectare.

Trade-offs with Agricultural Sustainability

Most contexts will see the emergence of critical trade-offs. The use of one asset for improvements can result in the depletion of another building a road to improve marketing near a forest can aid timber extraction. In some cases, progress in one component of a farm system may cause secondary problems, such as zero-tillage reducing soil erosion and conserving water, but still relying on applications of herbicides. There are also secondary problems that may arise in sustainable agriculture projects. These include i) land having to be closed off to grazing for rehabilitation, resulting in people with no other source of feed having to sell their livestock; ii) increased household workload, the burden particularly falling on women, if cropping intensity increases or new lands taken into cultivation; and iii) additional incomes arising from sales of produce may go directly to men in households, who are less likely than women to invest in children and the household as a whole.

There will also be new winners and losers with the emergence of widespread adoption of sustainable agriculture. This model for farming systems implies a limited role for current agro-chemical products, the producers of which are unlikely to accept market losses lightly. Sustainable livelihoods based on sustainable agriculture which increases the assets base may simply increase the incentives for more powerful interests to take over, such as landlords taking back formerly degraded land from tenants who had adopted sustainable agriculture. And sustainable livelihoods based on sustainable agriculture may appear to be keeping people in rural areas away from centres of power, and `modern society some rural peoples aspirations may precisely be to gain sufficient resources to leave rural areas.

On Policies for Sustainability

Several things are now clear with respect to agricultural sustainability:

The technologies and social processes for local level agro-ecological improvements are well-tested and established;

The social and institutional conditions for spread are less well-known, but have been established in several contexts (in particular social groups at local level and novel partnerships between external agencies;

The political conditions for the emergence of supportive policies are the least established, with only a very few examples of real progress.

Most of the agricultural sustainability improvements seen in the 1990s arose despite existing national and institutional policies, rather than because of them. Nonetheless, there has been some global progress towards the recognition of the need for policies to support sustainable agriculture. Although almost every country would now say it supports the idea of agricultural sustainability, the evidence points towards only patchy reforms. Only two countries, Cuba and Switzerland, have given explicit national support for a transition towards sustainable agriculture putting it at the centre of agricultural development policy and integrating policies accordingly. Cuba has a national policy for alternative agriculture; and Switzerland has three tiers of support for practices contributing to agriculture and rural sustainability.

Several countries have given sub-regional support, such as the states in southern Brazil supporting zero-tillage and catchment management, and some in India supporting watershed management or participatory irrigation management. A much larger number have reformed parts of agricultural policies, such as Chinas support for integrated ecological demonstration villages, Kenyas catchment approach to soil conservation, Indonesias ban on pesticides and programme for farmer field schools, Indias support for soybean processing and marketing, Bolivias regional integration of agricultural and rural policies, Swedens support for organic agriculture, Burkina Fasos land policy, and Sri Lanka and the Philippines stipulation that water users groups manage irrigation systems.

Agricultural systems can be economically, environmentally and socially sustainable. But without appropriate policy support, they are likely to remain at best localised in extent, and at worst simply wither away. We cannot, therefore, yet say whether a transition to sustainable agriculture, delivering increasing benefits at the scale occurring in these projects, will result in enough food to meet the current food needs of developing countries, the future basic needs after continued population growth, or the potential demand following adoption of more meat-rich diets. Even the substantial increases reported here may not be enough. However, there is scope for cautious optimism, as the evidence indicates that productivity can increase steadily over time if natural, social and human capital assets are accumulated.


J.M Lenn and D. Wood, Agrobiodiversity International, 13 Herons Quay, Milnthorpe, Cumbria LA7 7HW, UK

While genuine progress has been made during the last few decades, food security and malnutrition remain major problems particularly in many developing countries in Sub-Saharan Africa and South Asia. Excluding China, the number of food insecure people in the world increased in the 1990s. Clearly renewed effort and fresh approaches are needed if the International Development Targets are to be achieved. Improved, sustainable disease management strategies can contribute to these targets.

Diseases are critically important components of agroecosystems globally, for social, economic and biological reasons. Damaging diseases may reduce food production: world wide annual losses due to diseases are 25-30% of attainable production of principle food and cash crops, with developing countries experiencing the greatest losses. There is little wonder that farmers have laboured for millennia and plant pathologists have devoted more than 100 years to developing improved, appropriate and sustainable management strategies.

The science of ecology is defined as the study of the relations of organisms to one another (biotic) and to their physical environment (abiotic). Ecological approaches to managing diseases for global food security depend on managing both biotic and abiotic factors. That is, managing the interactions between food crops, pathogens and associated organisms as well as managing soil, water, and climatic factors in agroecosystems to minimize losses. The range of ecological approaches available to farmers for sustainable disease management is therefore substantial.

Ecological approaches to managing diseases are usually given a high profile and often considered to be most appropriate for traditional agricultural systems in developing countries. It is unfortunate that the interpretation of appropriate biotic approaches has become synonymous with maximizing diversity and that the importance of abiotic factors has been neglected. Diverse agroecosystems are thought to be more ecologically sound than less diverse systems while monocultures, the foundation of global food security, are regarded as ecologically dysfunctional. Much of this thinking is based on simplistic and even dogmatic ideas from the ecology of yesteryear overlain with environmental politics.

In this paper, we review different approaches to managing the interactions between food crops, pathogens, associated organisms and their physical environment to minimize losses. The contextual framework is the need to produce more food, more cost-effectively, less labour- and knowledge-intensively and more sustainably to achieve global food security and conserve the natural resource base. We look at management of the crop and its relationship with other organisms in the field and the landscape. We also look at how improved management of soil, water, and climatic factors can contribute to sustainable disease management. The reality is that farmers will make choices for disease management mainly based on sound socio-economic principles. It is these principles that will determine the ecological choices followed by farmers for sustainable disease management.


R. J. Hillocks and S. Eden-Green, Natural Resources Institute, Chatham.

The agricultural sector in sub-Saharan Africa provides on average, 70% of employment and 40% of export income. Many of those who derive their income from agriculture are small farmers living at, or little above subsistence level. Agriculture and rural development therefore, have the potential to play a central role in poverty alleviation and sustainable development. It has been estimated that food production must increase by 4% per annum just to maintain the present balance. Nevertheless, the overall commitment to research from the donor community has declined in recent years. What are the constraints, or perceived constraints, that have brought this about? Using plant disease management as a model, this is the first question that this paper attempts to answer. Since the beginning of the 1990s, there has been a groundswell of criticism of agricultural research that is seen to have failed to meet the needs of the small farmer. The perception in the donor community is that the outputs of research have not been widely adopted by farming communities. While this may be the case to some extent, there are examples of successful adoption of agricultural research outputs. Strategies can be implemented at the stage of project design, to develop the linkages and pathways for adoption of the intended outputs. The second question the paper addresses therefore, is; what are the barriers to adoption? Case studies are used to show how some of these obstacles to adoption can be overcome. The economic status of agricultural communities and the analysis of research adoption differ in Asia, Latin America and Africa. Sub-Saharan Africa is the worlds largest remaining area of chronic underdevelopment and it is from there that most of our examples will be drawn but some parallels are made from experiences of rural communities outside Africa.


S. Rajaram and H.J. Dubin CIMMYT

Beyond its enormous impacts on the worlds food supply, the so-called green revolution was an outstanding example of how genetic resources can be used effectively to dramatically improve crop plants and boost food production. The revolution marked the beginning of a technological transformation in the field of crop improvement that continues to this day. Since then, many new methods have been applied to develop modern crop varieties and systematically tap into novel sources of genetic diversity for desirable traits. For example, the improved yield potential, plant architecture, and resistance to different diseases that characterize modern crop varieties are possible thanks to the introgression of genes from many different sources, such as landraces, breeders working collections, and genetic resources conserved in genebanks. Techniques such as interspecific crosses (e.g., the spring x winter wheat genepools) and intergeneric crosses (e.g., between wheat and its wild relatives) have provided giant leaps in production and greatly improved traits such as disease resistance and drought tolerance. More recent improved varieties thus possess broader diversity and are less likely to succumb to diseases and environmental stresses. The free exchange of plant genetic resources has been and will continue to be essential to achieving these advances. However, in industrialized countries this freedom is being curtailed by the acquisition of different forms of intellectual property rights over plant genetic resources. If the trend continues, severely restricting the free exchange of germplasm, breeders will find it increasingly difficult to forge new, improved versions of crop species, which could have dire consequences for food production levels in the developing world. To offset this trend, both the CGIAR and FAO have established policies directed at ensuring that everyone, including farmers and public sector breeders in developing countries, has free access to plant genetic resources preserved in major genebanks at CGIAR commodity centers, where some of the worlds largest collections of crop genetic resources are stored. These banks have signed an agreement with FAO to conserve a major portion of these resources for the benefit of all humankind, which implies that no restrictions may be placed on them. These resources have the potential to contribute highly useful genes for the improvement of a plethora of crops, which should help bring about food security in resource-poor countries now and in the future. 


Martin Wolfe, Elm Farm Research Centre, UK

Comprehensive application of the principles of organic agriculture leads to production systems in which plant diseases (and pests and weeds) are often less severe than might be expected from experience of non-organic farming systems. However, progress needs to be made to reduce the levels, or their potentials, still further.

In terms of ecological agriculture, the reasons for the apparent reductions in disease are manifold. First, there are important interactions with the soil of organic rotations and methods of fertility building. Organically farmed soils are biologically more active and can be inherently less conducive to soil-borne diseases than are non-organically farmed soils. Furthermore, rotations in space and time, together with, for example, late planting, organic crop nutrition and general encouragement of beneficial organisms, can play a role in restricting the potential for foliar diseases.

However, to improve significantly on the current position, and to do so simultaneously for diseases, pests and weeds, needs a major increase in the understanding and application of functional biodiversity, principally through the many forms of inter-cropping. There is now considerable practical experience with variety mixtures and, to a lesser extent, with inter-cropping (even in the developed world), based on scientific experimentation and modelling. A number of mechanisms involved in various forms of mixed systems have been elucidated which help to demonstrate that such approaches can be both highly effective and sustainable in terms of the major criteria of environmental, economical and social acceptability.

To progress further, use should be made of recent studies that have been concerned with increasing awareness of the range of signalling systems that operate within and among species of plants, animals and microbes. These indicate that the potentials for positive interactions within mixed cropping systems, and for interactions with helper species, are considerable. One example is the production by many plants of methyl salicylate, a volatile form of salicylic acid, which has been shown to be important in the induction of resistance both to diseases and to pests in neighbouring, unattacked plants. We need to know whether there is useful variation in the production of, and sensitivity to, such resistance signalling systems among species and varieties that could be used as another tool for exploitation in sustainable inter-crop systems.

Crucially, the benefits from inter-cropping systems are not limited to control of diseases, pests and weeds. They can provide buffering against a wide range of other environmental variables. And, in terms of sustainability and food security, the diversity of produce from such systems can help to buffer the producer against unexpected variations in the market place.