The last decade for pesticides?

by David Barkin

[David Barkin is research director, Ecodevelopment Centre, Mexico City, and Full Professor of Economics, Universidad Auta Metropolitans, Xochimilco Campus. The research on which this article is based was conducted as part of the research programme of the Ecodevelopment Centre an institutional member of the Mexican Council for Science and Technology.]

Reliance on pesticides constitutes a fundamental part of prevailing agricultural technology. But increasingly, research by agronomists, plant breeders, and biotechnologists is offering new options which are bath more profitable and ecologically less pernicious. As these new technologies are developing, and pesticide technology is waning, it is not surprising to see a lively struggle among chemical companies, farmers, and the public over the use of pesticides. At present, restrictions on the use of pesticides are increasingly common and more effectively enforced in recognition of the dangers to workers in the fields and factories, to consumers, and to the environment.

The challenge to agriculturists concerned about practising a sustainable agriculture is to develop alternative approaches to pest control which reduce or eliminate the dangers of contamination and persistence in the environment inherent in the use of noxious agrochemicals, while limiting problems of infestation and resistance among potential pests. Concurrently, for the greatest number of the world's farmers - the smallholders of the Third World - the search for alternatives is not simply a response to dangers or restrictions: it is a necessity born of the lack of the economic wherewithal to implement the chemical approach to pest management.

When the high economic, human, and resource costs of pesticide dependency are considered alongside the growing problems, the case in support of a concerted effort to develop and implement new approaches to pest control becomes compelling. The World Bank recognized this need in its 1985 guidelines for project support: "Sound pest management should aim to reduce dependence on chemical pesticides through the establishment of economic control thresholds and through the use, wherever possible, of agronomic and related practices which reduce the severity of pest attacks." Thus, after a brief discussion of the pesticide problem, this article will focus on the constructive alternatives to the use of pesticides already available to enhance agricultural productivity. These alternatives take several different approaches: changing cultivation patterns to reduce the problem of infestation through crop rotation and biological controls; the introduction of integrated, non-chemical pest management programmes; and new forms of delivery of chemicals less pernicious to people and their environment.

The pesticide problem. Pesticides are lethal by definition. To be effective, they must be toxic. In some cases, they are specific to one organism, but in most they are deadly to a range of flora or fauna. Since the Second World War, the use of pesticides in agriculture has reshaped economic and social development. Their introduction and dissemination facilitated the opening of new regions to cultivation and the transformation of others to new crops. The impact was particularly dramatic in tropical and subtropical areas, where commercial agriculture often destroyed natural settings and traditional models of diversified cultivation.

Pesticides also offered a solution to another problem: how to incorporate the complex ecologies of diverse micro-environments into a more homogeneous pattern of resource management. Smallholder agriculture, which still predominates in most of the world, evolved from the complex interaction between human selection of plants for domestication and the environments in which cultivation occurred. Modern society has modified this interaction between culture, biology, and environment. Pesticides constitute a particularly powerful class of agents of such transformations. Their introduction into agriculture offered the possibility of simplifying cultivation practices by reducing the number of exogenous variables that had to be manipulated by the producer. By defining a broad variety of flora and fauna as "pests" and eliminating or suppressing them with synthetic substances, modern agriculturists did not have to acquire the broad base of knowledge and wide variety of techniques which the "traditional" cultivator inherited. Thus, pesticides accelerated the pace of monocropping, which in turn was part of rural insertion into the internationalized production system.

These transformations are viewed with favour among a substantial part of the commercial and research communities in agriculture. In contrast, those concerned about the welfare and survival of the world's small farmers have been concerned that the high costs of pesticides has made them inaccessible for most smallholders. In the long run, however, this may turn out to be a blessing in disguise, for even the fervent supporters of pesticides are beginning to recognize their drawbacks and to reassess the value of the traditional farmers' techniques. The pesticides are toxic not only to the creatures they are intended to attack. They also strike other living organisms, including the workers who manufacture and apply them and the ultimate consumers of the food products. And they accumulate in the soil and water, thereby posing a growing threat into the future. An additional problem stems from the fact that pesticides can kill off the natural predators of the "pests", so that the applicators find themselves in a vicious circle, requiring more chemicals to control the growing scourge. Still worse from the point of view of the commercial farmer, their effectiveness is diminishing with time as the targets develop resistance to their toxicity, rendering the chemicals useless.

Alternatives to pesticide technology. Until recently, most of the critical literature on pesticide use has called for an end to synthetic pesticides, with few proposals for alternatives. However, many researchers have now begun to study the techniques used by farmers in confronting pest problems during the generations before the advent of synthetic chemical compounds; others have documented the use of modern methods.

In the following sections, some examples will be discussed as part of a review of the directions of current and future work in this area.

a) Changing cultivation practices and patterns. One of the most widely recognized sources of concern in agriculture is the potential damage from plagues associated with intensive cultivation of a single commercial crop in a concentrated area. This problem is particularly serious in the cultivation of cotton, which demands more insecticides than any other single crop. In most regions it shows a typical pattern in which exclusive reliance on chemicals works well over a short period (from 5 to 15 years), only to require increasing dosages and more frequent applications as the pests gain resistance, until they can no longer be controlled economically, if at all. Several different strategies, involving a combination of methods, have been used to confront the problem. The experience in Peru in the 1950s is particularly illustrative of an effective eclectic approach. There, cotton cultivation was threatened by declining yields as a result of the reduced efficacy of the synthetic chemicals. Instead of attempting a different range of chemicals, the enlightened authorities banned the use of synthetic organic pesticides, reintroduced beneficial insects, and "mandated the adoption of certain cultural practices, such as early maturing varieties, establishing deadlines for planting, and destroying crop residues". As a result of this programme, primary pest outbreaks declined dramatically in intensity and cotton yields rose 30 per cent over previous levels.

The inclination to combat plagues with synthetic chemicals is so ingrained that alternative approaches are often strongly resisted by scientists and planters alike. Thus, when the United Fruit Company found that its Costa Rican plantations were infested by two insects, it immediately resorted to the aerial and ground application of insecticides. Continued problems with insects were met with more intensive applications without success. The original group of entomologists was subsequently replaced by others who called for a drastic reduction in the use of synthetic agents. Only after some 15 years of work and experiments with smaller applications were the ecologically oriented entomologists able to convince the company to take "a bold step" of stopping all insecticide spraying. Within two years, the pest problem disappeared. The success of the programme was enhanced by the proximity of nearby forests that provided refuge for the natural enemies of the pests during the years of intensive applications of pesticides, offering evidence of the importance of environmental diversity in a programme of ecological control.

Diversified ecologies and cultivation patterns and practices are well suited to the nutritional and other needs of smallholder populations. For example, the highly productive chinampa system, developed by the pre-Columbian populations of Mexico, "incorporates interplanting of crops in unusually sophisticated ways, mimicking the natural conditions of the humid rainforest and thereby controlling for moisture, nutrients, light absorption, and pests." In the highland areas of Mexico interplanting and varietal selection for resistance to pests and weather variation are all elements in the traditional agricultural system. Fortunately, these practices persist in spite of the onslaught of modern technology, especially in those regions where commercial agriculture has not been sufficiently profitable to draw people from the security of their traditional approaches to food production.

More research is needed on diversified cropping systems. But even with our rudimentary knowledge, it is apparent that such systems offer great potential for minimizing the damage from pests while also enhancing agriculture's ability to meet the world's food needs and improve the incomes of small farmers.

b) Integrated pest management. A different approach to pest control in cotton, using "trap crops", has also been proven as a means to reduce pesticide use. A programme in Nicaragua demonstrated the effectiveness of preceding the regular planting season with the introduction of small plots which would be used to attract pest populations, especially the boll weevil, where they could be attacked by intensive applications of insecticides as part of a broader "Integrated Pest Management" (IPM) programme. The programme "reduced subsequent pesticide applications by 30 per cent and produced a cotton yield nearly 15 per cent higher" than in fields using traditional chemical approaches to pest control. This was complemented by "dense seeding to obtain a high plant population resistant to damage by soil pests, and scouting at three- to four-day intervals by trained field aides to monitor the growth and development of the cotton plants and determine the status of pests and activity of natural enemies." This approach requires "area-wide implementation for success because key pests are widely distributed and highly mobile over the cottongrowing area."1 "But unlike certain self-perpetuating biological pest controls, IPM for cotton requires constant vigilance.... The system requires, beyond good design, adequate education and rewards for human organisms that keep it running."

Similar techniques have been used elsewhere with striking success. Brazilian agricultural researchers sought help from US colleagues in controlling infestations in soybeans. National research organizations and international sources joined to create a programme which defined "economic thresholds" below which the presence of pests could be tolerated without a decline in yield or seed quality. Only when infestations exceeded this level would minimal dosages of non-persistent pesticides having the least detrimental effect on natural enemies be applied. As a result of the IPM programme, pesticide applications on soybeans decreased by 80-90 per cent between 1975 and 1982.

A beetle infestation of coconut palm, a major source of the world's edible oil with multiple other uses in the tropics, inspired a group of FAO scientists to develop a biological control programme based on the use of a lethal virus that attacked the larvae. The disease, which caused millions of dollars of damage annually, was identified in 1953. By 1979 the problem had been controlled to such an extent that the programme was terminated.

Another case of biological controls is the fight against the mealybug, which affects cassava planting among subsistence producers in Africa. Initially, in spite of the fact that cassava is a fundamental part of the diet of millions, it was ignored by the international agricultural community because it was not an important cash or food crop in the temperate zones. But when pests began to cause widespread devastation, the search for some natural enemy became urgent. As a result of a coordinated international effort, scientists were able to find a wasp that was a particularly effective natural enemy of the mealybug. The success of this project has been held back by the difficulty of propagating the wasp as fast as required in the many African countries which are "desperately waiting for releases". Another problem with this biological agent, as with most others, is that it is "very cheap to maintain, but extremely expensive to develop and initially distribute. Since there is no long-term potential for profit, multinational corporations will rarely, if ever, invest in this type of control.... The case serves to underline the need for generous investments by governments, and the high return, in human terms, such investments can yield."

The potential benefits of IPM are not limited to the developing countries. Even among the highly commercialized fruit and vegetable growers of the US state of Florida, the use of biological agents is widely accepted as an environmentally more benign approach to pest control. Although some of these agents are being created with genetic engineering techniques most of them are likely to be found naturally occurring.

c) New forms of pesticide delivery. The agrochemical companies are developing new strategies to meet the criticisms of chemical pesticides and to defend their markets. The groundwork for this move has been set with the gradual assimilation of many independent seed companies by transnational corporations active in other agricultural input markets. With this integration, the companies have been modifying seeds through varietal selection and genetic manipulation to make the crops more resistant to certain pests and also to induce resistance to certain chemicals which can then be applied to control the spread of other plagues affecting that crop.6

This technology is most advanced in the area of developing herbicide tolerant plant crops using a patented "aroA gene" "which permits more widespread and frequent use of herbicides for post-emergent weed control while reducing the need for pre emergent application".'' Although industry spokespeople argue that this will reduce the need for tillage (as part of a change in grain technology in dryland farming) and therefore lower groundwater contamination, a commentator pointed out that this innovation will lead to greater herbicide use and therefore more releases of toxic substances and accumulation in the environment.

Another approach is to bundle seeds in a "cocoon" package including appropriate (proprietary) chemicals to assure the timed release of fertilizers and pesticides appropriate for specific environmental conditions. Advocates say that with this specific targeting, smaller doses of synthetic chemicals will be required, while the profits of the chemical companies will be greater.

The handwriting on the wall. Although pesticides continue to be used as part of the struggle for higher productivity, increasing pressures from groups concerned with the environment will combine with the economic logic of the profit equation to push farmers and researchers to search for alternative ways to handle pest control problems. At present, technology is not always contributing to progress in this direction. For example, herbicide use is increasing with the "minimum tillage" movement. But there is increasing recognition of the need to promote techniques to raise productivity without using environmentally damaging chemicals and practices. With this understanding, alternatives to the prevailing models of "modern" and "commercial" cultivation practices are being adopted along with other approaches to pest control. Many of these involve a belated appreciation of the wisdom of "traditional" farming systems.

It remains to be seen whether industry responses to the criticisms of present pesticide technologies are effective approaches to confront the economic and environmental problems. The companies themselves see the handwriting on the wall: present pesticide practices have proved to be socially unacceptable, technologically inefficient, and economically unsound, and alternative solutions must be developed for a more sustainable agriculture.