Pesticides kill pests, but also pests’ natural enemies, and their overuse can harm farmers, consumers and the environment. The first line of defence is a healthy agro-ecosystem
Plant pests are often regarded as an external, introduced factor in crop production. That is a misperception, as in most cases pest species occur naturally within the agro-ecosystem. Pests and accompanying species – such as predators, parasites, pollinators, competitors and decomposers – are components of crop-associated agro-biodiversity that perform a wide range of ecosystem functions. Pest upsurges or outbreaks usually occur following the breakdown of natural processes of pest regulation.
Because intensification of agricultural production will lead to an increase in the supply of food available to crop pests, pest management strategies must be an integral part of SCPI. However, they will also need to respond to concerns about the risks posed by pesticides to health and the environment. It is important, therefore, that potential pest problems associated with the implementation of SCPI are addressed through an ecosystem approach.
Although populations of potential pests are present in every crop field, every day, regular practices, such as crop monitoring and spot control measures, usually keep them in check. In fact, the total eradication of an insect pest would reduce the food supply of the pest’s natural enemies, undermining a key element in system resilience. The aim, therefore, should be to manage insect pest populations to the point where natural predation operates in a balanced way and crop losses to pests are kept to an acceptable minimum.
When that approach does not seem sufficient, farmers often respond by seeking additional protection for their crops against perceived threats. The pest management decisions taken by each farmer are based on his or her individual objectives and experiences. While some may apply labour-intensive control measures, the majority turn to pesticides. In 2010, worldwide sales of pesticides were expected to exceed US$40 billion. Herbicides represent the largest market segment, while the share of insecticides has shrunk and that of fungicides has grown over the past ten years1.
As a control tactic, over-reliance on pesticides impairs the natural crop ecosystem balance. It disrupts parasitoid and predator populations, thereby causing outbreaks of secondary pests. It also contributes to a vicious cycle of resistance in pests, which leads to further investment in pesticide development but little change in crop losses to pests, which are estimated today at 30 to 40 percent, similar to those of 50 years ago2. As a result, induced pest outbreaks, caused by inappropriate pesticide use, have increased3.
Excessive use of pesticide also exposes farmers to serious health risks and has negative consequences for the environment, and sometimes for crop yields. Often less than one percent of pesticides applied actually reaches a target pest organism; the rest contaminates the air, soil and water4.
Consumers have grown increasingly concerned about pesticide residues in food. Rapid urbanization has resulted in the expansion of urban and peri-urban horticulture, where pesticide use is more evident and its overuse even less acceptable to the public. The serious consequences of pesticide-related occupational exposure have been amply documented among farming communities, heightening social sensitivity towards agricultural workers’ rights and welfare.
Public concerns are being translated into more rigorous standards both domestically and in international trade. Major retailers and supermarket chains have endorsed stricter worker welfare, food safety, traceability and environmental requirements. However, weak regulation and management of pesticides continue to undermine efforts to broaden and sustain ecologically-based pest management strategies. That is because pesticides are aggressively marketed and, therefore, often seen as the cheapest and quickest option for pest control.
Farmers would benefit from a better understanding of the functioning and dynamics of ecosystems, and the role of pests as an integral part of agro-biodiversity. Policymakers, who are often targets of complex information regarding crop pests, would also benefit from a better understanding of the real impact of pests and diseases in cropping ecosystems.
Integrated pest management
Over the past 50 years, integrated pest management (IPM) has become and remains the world’s leading holistic strategy for plant protection. From its first appearance in the 1960s, IPM has been based on ecology, the concept of ecosystems and the goal of sustaining ecosystem functions5-7.
IPM is founded on the idea that the first and most fundamental line of defence against pests and diseases in agriculture is a healthy agro-ecosystem, in which the biological processes that underpin production are protected, encouraged and enhanced. Enhancing those processes can increase yields and sustainability, while reducing input costs. In intensified systems, environmental factors of production affect the prospects for the effective management of pests:
- Soil management that applies an ecosystem approach, such as mulching, can provide refuges for natural enemies of pests. Building soil organic matter provides alternate food sources for generalist natural enemies and antagonists of plant disease and increases pest-regulating populations early in the cropping cycle. Addressing particular soil problems, such as salt water incursion, can render crops less susceptible to pests such as the rice stem borer.
- Water stress can increase the susceptibility of crops to disease. Some pests, notably weeds in rice, can be controlled by better management of water in the production system.
- Crop varietal resistance is essential for managing plant diseases and many insect pests. Vulnerability can arise if the genetic base of host plant resistance is too narrow.
- Timing and spatial arrangement of crops influence the dynamics of pest and natural enemy populations, as well as levels of pollination services for pollinator-dependent horticultural crops. As with other beneficial insects, reducing pesticide applications and increasing diversity within farms can increase the level of pollination service.
As an ecosystem-based strategy, IPM has achieved some notable successes in world agriculture. Today, large-scale government IPM programmes are operational in more than 60 countries, including Brazil, China, India and most developed countries. There is general scientific consensus – underscored by the recent International Assessment of Agricultural Science and Technology for Development8 – that IPM works and provides the basis for protecting SCPI. The following are general principles for using integrated pest management in the design of programmes for sustainable intensification.
- Use an ecosystem approach to anticipate potential pest problems associated with intensified crop production. The production system should use, for example, a diverse range of pest-resistant crop varieties, crop rotations, intercropping, optimized planting time and weed management. To reduce losses, control strategies should take advantage of beneficial species of pest predators, parasites and competitors, along with biopesticides and selective, low risk synthetic pesticides. Investment will be needed in strengthening farmers’ knowledge and skills.
- Undertake contingency planning for when credible evidence of a significant pest threat emerges. That will require investment in seed systems to support deployment of resistant varieties, and crop-free periods to prevent the carryover of pest populations to the following season. Selective pesticides with adequate regulatory supervision will need to be identified, and specific communication campaigns prepared.
- Analyse the nature of the cause of pest outbreaks when problems occur, and develop strategies accordingly. Problems may be caused by a combination of factors. Where the origin lies in intensification practices – for example, inappropriate plant density or ploughing that disperses weed seeds – the practices will need to be modified. In the case of invasions by pests such as locusts, methods of biological control or disease suppression used in the place of origin can be useful.
- Determine how much production is at risk, in order to establish the appropriate scale of pest control campaigns or activities. Infestation (not loss) of more than 10 percent of a crop area is an outbreak that demands a rapid policy response. However, risks from pests are often over-estimated, and crops can to some extent compensate physiologically for pest damage. The response should not be disproportionate.
- Undertake surveillance to track pest patterns in real time, and adjust response. Georeferenced systems for plant pest surveillance use data from fixed plots, along with roving survey data and mapping and analysis tools.
The way forward
The “business as usual” approach to pest management, still followed in many countries and by many farmers, limits their potential for implementing sustainable crop production intensification. Improvements in agro-ecosystem management can help avoid indigenous pest outbreaks, respond better to pest invasions and reduce risks from pesticides to both human health and the environment. Entry points for improved ecosystem-based pest control include:
- a major pest or disease outbreak that threatens food security;
- food safety concerns arising from high levels of pesticide residues in farm produce;
- incidences of environmental pollution or human poisoning;
- striking losses of beneficial species, such as pollinators or birds;
- pesticide mismanagement, such as the proliferation of obsolete pesticide stockpiles.
In each of these cases, there is need for a pest control strategy that can be sustained and does not produce adverse side effects. After a nationally or regionally recognized pest problem has been brought under control with IPM, policymakers and technical staff are usually much more receptive to the approach, and also more willing to make the necessary policy and institutional changes to support it in the long term. The changes may include removal of pesticide subsidies, tighter enforcement of pesticide regulations, and incentives for local production of IPM inputs, such as insectaries for natural predators.
Countries should give preference to less hazardous pesticides in registration processes. They should also ensure that they apply ecologically informed decision-making to determine which pesticides may be sold and used, by whom and in what situations. Eventually, pesticide-use fees or pesticide taxes, which were pioneered in India in 1994, may be used to finance the development of alternative pest management practices and subsidize their adoption.
|Changing perceptions of emergencies that involve pest or disease outbreaks|
|Perceptions||"Business as usual"||Ecosystems approach|
Policymakers can support SCPI through IPM programmes at a local, regional or national scale. They should be aware, however, that the success of effective pest management using IPM techniques depends ultimately on farmers. It is they who make key management decisions on the control of pests and diseases. Policy instruments include:
- Technical assistance and extension support to farmers in applying ecologically based management practices and developing and adapting technologies, taking into account their local knowledge, social learning networks and conditions.
- Targeted research in areas such as host plant resistance to pests and diseases, practical monitoring and surveillance methods, innovative approaches to field pest management, the use of selective pesticides (including biopesticides) and biocontrol.
- Private sector regulation, including effective systems of governance for the registration and distribution of pesticides (specifically covered by the International Code of Conduct on the Distribution and Use of Pesticides).
- Removal of perverse incentives such as pesticide price or transport subsidies, the unnecessary maintenance of pesticide stocks, which encourages their use, and preferential tariffs for pesticides.
Large-scale adoption of ecosystem approaches would provide opportunities for small local industries. The scaling up of ecological pest management practices can be expected to increase demand for commercial monitoring tools, biocontrol agents such as predators, parasitoids or sterile organisms, pollination services, microorganisms and biopesticides. Today, private companies produce more than 1000 bio-products, worth some US$590 million in 2003, based on bacteria, viruses, fungi, protozoa and nematodes9. This local industry would expand significantly with a shift to a more ecosystem-centric approach.
From the perspective of the food processing industry, more stable and sustainable agro-ecosystems will result in a more consistent and reliable supply of agricultural produce free of pesticide residues. Additionally, labelling food products with an IPM or similar label can help ensure access to new markets for producers.
Sustaining IPM strategies requires effective advisory services, links to research that respond to farmers’ needs, support to the provision of IPM inputs, and effective regulatory control of chemical pesticide distribution and sale. One of the most effective means of promoting IPM at local level is the farmer field school, an approach that supports local learning and encourages farmers to adapt IPM technologies by drawing upon indigenous knowledge. Farmers need ready access to information on appropriate IPM inputs. The adoption of IPM can be accelerated by using, for example, cellular phones to supplement traditional methods of outreach, such as extension, media campaigns and local inputs dealers.
1. Rana, S. 2010. Global agrochemical market back in growth mode in 2010. Agrow (www.agrow.com).
2. Lewis, W.J., van Lenteren, J.C., Phatak, S.C. & Tumlinson, III, J.H. 1997. A total system approach to sustainable pest management. Proc. Natl. Acad. Sci., 94(1997): 12243–12248.
3. Wood, B.J. 2002. Pest control in Malaysia’s perennial crops: A half century perspective tracking the pathway to integrated pest management. Integrated Pest Management Reviews, 7: 173-190.
4. Pimentel, D. & Levitan, L. 1986. Pesticides: Amounts applied and amounts reaching pests. BioScience, 36(2): 86-91.
5. Stern, V.M., Smith, R.F., van den Bosch, R. & Hagen, K.S. 1959. The integrated control concept. Hilgardia, 29: 81-101.
6. FAO. 1966. Proceedings of the FAO Symposium on Integrated Pest Control, Rome, 1965. Rome, FAO.
7. Smith, R.F. & Doutt, R.L. 1971. The pesticide syndrome– diagnosis and suggested prophylaxis. In C.B. Huffaker, ed. Biological Control. AAAS Symposium Proceedings on Biological Control, Boston, December 1969, pp. 331-345. New York, Plenum Press.
8. IAASTD. 2009. Agriculture at the crossroads, by B.D. McIntyre, H.R. Herren, J. Wakhungu & R.T. Watson, eds. Washington, DC.
9. Guillon, M. 2004. Current world situation on acceptance and marketing of biological control agents (BCAS). Pau, France, International Biocontrol Manufacturer’s Association.
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