AGRITRENDS: Bombs in the food chain

(Second of Two Parts)

“Over the years, a costly war has gone on between insects and man… Even if we pour billions of pesos worth of pesticides, we cannot totally wipe out all insect pests.” – Dr. Rodolfo P. Estigoy


It was a case of sibling rivalry. Brothers Gerry and Ronnie Estrera both raise citrus in their respective farms. Five years ago, their rivalry took an unusual turn when they made a deal.

Gerry, a committed environmentalist, challenged Ronnie that he could harvest as Ronnie’s without using pesticides. “I was told that it would be impossible; my brother was absolutely petri¬fied,” he recalled.

Ronnie, who farmed an adjacent citrus orchard, kept using the tradition¬al chemical sprays.

The Estrera brothers enlisted a researcher from the nearby university to determine whose mangoes were better: Gerry’s organi¬cally grown citrus or Ronnie’s conventionally grown ones.

“The number of fruits damaged by insects was just about the same in both orchards,” the study reported. In simpler terms, Gerry’s organic pest-control techniques proved equal to Ronnie’s conventional chemical spraying. Ronnie was impressed enough that he has now stopped using pesticides altogether.

Chemicals are used by farmers to control pests that attack agricultural crops. “Each year, an estimated half of the world’s critically short food supply is consumed or destroyed by insects, molds, rodents, birds, and other pests that attack foodstuffs in fields, during shipment and in storage,” wrote Jane E. Brody in “The New York Times.”

“An estimated one-third of the world’s food supply would be lost each year to weeds, insect pests, and diseases if crop protection chemicals were not used. This is enough to feed about two billion people,” said the US Agricultural Retailers Association in a statement.

In the Philippines, reports said 62% of pesticides sold are in the form of insecticides. Of these, 46% are applied to rice and 20% to vegetables. Insecticides had become one of the major expenses of farmers that account for about 40% of total production cost.

Roy C. Alimoane, director of the Davao-based Mindanao Baptist Rural Life Center, said that people who are eating chemical-laced vegetables are risking their lives since chemicals are not always dissipated. Generally, chemicals are accumulated in the human body.

The lack of regulation in most developing countries often accounts for the importation of banned pesticides. In some instances, farmers try to apply untested chemicals which they think could drive away insects and pest. In 1992, the illegal use of cyanide compounds by cabbage farmers in the Cordillera region provoked a public outcry.

Despite the health and environmental risks, farmers are still hooked on many of the worst offenders. Without pesticides, they claim, their costs would skyrocket, harvests would plummet, and more people would go hungry. It is widely assumed that for big harvests, pesticides are essential. After all, it is noted, farmers in industrial coun¬tries apply more pesticides, lose less to pests, and reap higher yields than farmers in developing countries.

A closer look at the data, however, indicates that pesti¬cides are not as essential as many people think, according to a study conducted by the Laguna-based International Rice Research Institute (IRRI).

The IRRI study looked on the effects of pesticides on rice produc¬tivity and health. Findings of the research showed that farmers’ earnings from chemically-treated crops are often greatly reduced by the cost of treating pesti¬cide-related health problems.

“The value of the crops lost to pests is invariably lower than the expense of treating pesticide-caused ailments,” said the head of the research team. “When health costs are factored in, the use of correct rice varieties and reliance on natural control by predators and parasites is the least expensive pest control strategy.”

The increasing awareness of the dangers posed by chemical pesticides to human health is prompting many Filipino farmers to use botanical formulations that they themselves are preparing,” said a position paper written by L. Masana and A. Manuel.

“Natural pest controls like the botanicals are safer to the user and the environment because they break down into harmless compounds within hours or days in the presence of sunlight,” wrote Eric Vinje in “Planet Natural.” “They are also very close chemically to those plants from which they are derived, so they are easily decomposed by a variety of microbes common in most soils.”

At the University of the Philippines at Los Baños (UPLB), scientists are developing a variety of insecticidal compounds that are not only safe and effective but, being biodegradable, nondestructive to the environment.

“We are looking for the biologically active constituents in the plants that could either kill, repel, or act as feeding deterrent or growth inhibitor,” explained Dr. Belen M. Rejesus, who was named as Outstanding Agriculture Scientist in 1990.

A leading example is black pepper. When grounded, black pepper contains one active property which is just as effective as Malathion, a chemical insecticide. Its residual toxicity, according to Dr. Rejesus, lasts up to four months against the weevil, a scourge of corn farmers.

Another one is the red pepper, known among Filipinos as “siling labuyo.” UPLB researchers found that extracts from the freshly chopped red pepper protect rice and corn grains against weevils and red flour beetles.

Many plants have insecticidal properties. Extracts of these plants can be sprayed on the crop to either kill or repel insects. “Tubli,” for instance, has an ancient reputation as a botanical pesticide. Ethnic groups in the Philippines have long been using it to poison unwanted fish. In Brazilian rivers, it is used to eliminate the deadly piranha.

Applied as a powder or spray, “tubli” is toxic to a wide range of insect pests – aphids, beetles, borers, the diamondback moth, fruit flies, thrips, cabbage worms, fleas, flea beetles, lice, loopers, mites, mosquitoes, psyllids, and slugs. It is recommended for application on bush and vine crops.

Another excellent botanical pesticide is “kakawate” or “madre de cacao.” The United Nations Food and Agriculture Organization (FAO) reports that “kakawate” leaves contain coumarin, which can be converted into an anticoagulant “discoumerol” found to be an efficient rat killer.

Aside from rodents, “kakawate” also acts potently on insects. In many countries, its leaves are placed in chicken runs, or left to soak in hot water and used to eliminate fleas and lice on domestic animals.

In Science City of Muñoz, organic rice farmers sprayed their crops with fermented leaves and twigs of “kakawate” and neem trees to control pests and diseases. Some farmers found it convenient and effective, too, to just allow the “kakawate” leaves to drift to their farm when they irrigate.

Actually, farmers need not to use pesticides – whether natural or synthetic – to obliterate pests. This is particularly true to farmers who are growing rice, according to Dr. K.K. Heong, an entomologist who used to work at IRRI.

All pesticides kill even those beneficial insects that are vital to the rice ecosystem, he said. “It is always the function that matters, not where it was derived,” Dr. Heong explained. “Be it botanically or chemically produced, if its function is to kill, then it is harmful to the whole food web in the rice ecosystem.”

One good way to avoid using pesticides is by relying on “Bacillus thuringiensis” (Bt) to do the work. Bt is a common soil bacterium so called because it was first isolated in the Thuringia region of Germany. It produces a protein that paralyzes the larvae of some harmful insects.

Scientists, through genetic engineering, have taken the Bt gene responsible for the production of the insecticidal protein from the bacterium and incorporated it into the genome of plants. As such, the plants have a built-in mechanism of protection against targeted pests.

Among the crops where Bt is introduced include corn, cotton, poplar, potato, rice, soybean, tomato, and more recently eggplant. “The protein produced by the plants does not get washed away, nor is it destroyed by sunlight,” said a briefing paper published by the Global Knowledge Center on Crop Biotechnology. “The plants are protected from the insects round the clock regardless of the situation.”

Since Bt crops are able to defend themselves against pests, the use of chemical insecticides is significantly reduced. A study conducted by the United States Department of Agriculture showed that 8.2 million pounds of pesticide active ingredients were eliminated by the farmers who planted Bt crops in 1998.

There are other ways farmers can protect their crops from pests, according to Alimoane. These include tilling (which exposes pests that live in the soil and increases soil aeration), crop rotation (it stops the build-up of microorganisms around plant roots), crop combination, and companion planting.

To use or not to use pesticides, that is the question. Some farmers say they will while other chorus they won’t. “While the use of chemical pesticides in agriculture cannot be totally discontinued,” Francisco C. Cornejo, then the administrator of Fertilizer and Pesticide Authority, told this author, “minimization, however, is probable.”

Meanwhile, William T. Vorley, in a briefing paper published by the International Institute for Environment and Development, wrote: “The global market value for pesticides use to protect national food security in developing countries (rather than to protect export feed, fiber and plantation crops) is rather trivial by global standards.”

Vorley also wrote: “Pesticides are among the technologies which have contributed to inexorable shift in agricultural activities away from the farm. The share of farming in the value added to agriculture has been in steady since at least 1920.” –