June 15, 1995

New Study Finds Indiscriminate Spraying of Bean Crops, Few Protective Precautions in Three-Country Andean Region

WASHINGTON, D.C.--A three-year study of bean farmers in the Andean regions of Colombia, Ecuador, and Peru has found that these farmers could reduce their insecticide use by as much as 70 percent without lowering yields through a system known as integrated pest management (IPM). The study, which was sponsored by the Colombia-based International Center for Tropical Agriculture (CIAT) and the Canada-based International Development Research Centre (IDRC), found that farmers spray beans, the most important legume crop in the region, with excessive amounts of highly toxic chemicals and take virtually no protective precautions.

The announcement was made today at an international conference, A 2020 Vision for Food, Agriculture, and the Environment. The conference was cosponsored by the International Food Policy Research Institute, a Washington, D.C.-based research group, and the National Geographic Society. More than 500 participants from 50 countries attended the conference to share research and solutions for preventing hunger while protecting the environment to the year 2020.

"The study's findings will have great implications for the farmers, their families, and large populations of people living in the urban areas who consume the crops grown in the Andes," said Cesar Cardona, lead researcher for the study and an entomologist with CIAT. "We know that the chemicals have poor health effects, and our study shows that these farmers will be able to reduce the destructive use of chemicals while keeping the same yields as before and spending less money."

"We also hope our findings will influence the use of chemicals on other crops," continued Cardona. "The problem of overuse of insecticides in the Andean region does not exist just in bean farming. Farmers apply chemicals more than 10 times a season on beans, potatoes, vegetables almost anything that's green."

The three-year feasibility study and planned implementation program seek to reduce economic losses, prevent ecological damage, and reduce toxicological risks to farmers and consumers in the three-country Andean region. The study, a collaborative effort between researchers and farmers, is based on 129 experiments with bean farmers, which took place from 1991 to 1994.

The study was conducted in the areas of Sumapaz and Oriente Antioque¤o in Colombia, the Chota River Valley and Loja in Ecuador, and Chiclayo and Chincha in Peru on 300,000 hectares of land planted with snap and dry beans. Bean production in these regions supplies the bean requirements of large urban centers, including Bogot  and Medell¡n in Colombia, Ibarra and Guayaquil in Ecuador, and Lima and Chiclayo in Peru.

IPM encourages the use of biological controls often in the form of natural predators to combat pests and diseases. The technique also relies on the strategic and sparing use of chemicals only when pest populations reach economically damaging levels. The study showed that in many cases natural control was more profitable than chemical control.

As part of the study, CIAT conducted a diagnostic survey of some 900 bean farmers in the target area. The survey found that "an incredible 100 percent of the farmers sprayed their crops on a regular basis." Many growers were spraying their crops up to 24 times per 90- to 100-day season that is, every 3 to 4 days. The survey found that heavy use of insecticides has killed the natural predators of many insects. Overuse has also generated widespread resistance to chemicals among many insect populations, thereby undermining the productivity of crops in the region.

"Farmers in this region who apply insecticides say, 'Voy a bañar el cultivo' (I am going to bathe the crop)," said Cardona. "It is rare for farmers in other parts of the developing world to use so many insecticides. We could not believe it when we realized that this had become a way of life in the Andes."

Most of the insecticides being used are highly toxic. Survey results found that few farmers seemed to be aware of the risks. Women were not directly involved in spraying operations, but children were occasionally seen helping their parents prepare mixtures and operating knapsack sprayers. While the majority of the farmers said they take precautions such as washing their hands or taking a shower after spraying, virtually none used protective clothing. Many ate, drank, or smoked while spraying. Up to 30 percent of the farmers surveyed said that they had suffered from chemical intoxication nausea, vomiting, tremors, and excessive sweating soon after spraying at least once in the past 10 years.

Farmers in the region spray for greenhouse whitefly, Trialeurodes vaporariorum; leafminer, Liriomyza huidobrensis; and pod borers, Epinotia aporema and Laspeyresia leguminis. In many cases, the insect damage does not justify chemical spraying.

Whitefly, which weakens the bean plant by sucking sap from the phloem, was a serious threat in the late 1980s, but no significant yield losses have been found since then. Farmers, however, continue to use insecticides against whitefly. When asked why, half of the survey respondents said they spray on a calendar basis; 25 percent said they spray simply because "they are used to doing it"; and 13 percent said "the crop always needs to be sprayed." All farmers reported that they applied chemicals regardless of insect damage or population levels, and all said they are very much afraid of whitefly damage.

Leafminer larvae burrow tunnels in the leaves of the bean plant, affecting the plant's appearance but not its yield. Nevertheless, farmers spray against this pest excessively. By raising the leafminers' resistance to chemicals and killing their natural predators, this spraying has generated an outbreak of leafminers that is essentially man-made. The CIAT study has found that the preservation of natural predators would be a far better method of control.

Finally, pod borers eat developing bean pods, but, in general, the damage they cause is too minimal to merit chemical control.

In the case of the leafhopper (Empoasca kraemeri), however, farmers have not been doing enough. The leafhopper causes stunted growth and yellowing of leaves. Farmers often interpret these symptoms as indicators of soil infertility instead of damage by insects, and they do not spray. Through the CIAT program, they are learning to recognize infestation and are advised to spray at a certain level of infestation.

When offered a simple plan for reducing insecticide use, 78 percent of the farmers surveyed expressed interest in the idea and were willing to learn. "The farmers are tired of using so many chemicals, and are willing to change," said Cardona. Therefore, a second phase of the study will encourage farmers to adopt a newly developed IPM system. This system includes (1) destruction of insect-drawing crop residue after harvesting; (2) judicious spraying of insecticides against whiteflies, leafhoppers, and pod borers through the use of simplified "action thresholds" (farmers estimate insect populations and damage levels from a small sample of crop leaves and spray only if the total is over a certain level); (3) preservation and exploitation of natural enemies for control of leafminers; (4) use of the natural bacteria Bt, or Bacillus thuringiensis, in a spray to control certain pests; (5) use of fungicides at 10- to 15-day intervals; and (6) use of traps to kill whiteflies and adult leafminers.

Until now, few of the farmers have received technical assistance from extension services; instead they have made their own decisions about the insecticides to be used and the rate and timing of applications. According to the study, many farmers rely heavily on the advice of pesticide company representatives. Salespeople were observed visiting each farmer on a regular basis, and insecticides were heavily advertised in the area. To counteract this lack of information and to promote the IPM system, the CIAT effort has printed 2,000 leaflets, 1,500 extension bulletins, and 1,000 booklets, and created a demonstration video. Participatory research activities and dissemination campaigns continue.

CIAT is dedicated to the alleviation of hunger and poverty in developing countries of the tropics. CIAT applies science to agriculture to increase food production while sustaining the natural resource base. CIAT is one of 16 international agricultural research centers sponsored by the Consultative Group on International Agriculture Research (CGIAR).

The IDRC is a Canadian public corporation that, since 1970, has helped researchers in developing countries find realistic solutions to problems in their communities in the fields of environment and natural resources.