Chemical Pesticides Kill More Than Bugs
BY AWAKE! CORRESPONDENT IN BRAZIL
“IT’S perfect,” says farmer Domingos dos Santos as he looks over his crop of cassava plants on his farm in southern Brazil. He has reason to be satisfied. The leaves of his plants look as if no harmful insect has ever set foot on them. Another feat of chemical insecticides? No. “Last year and this year,” says Domingos, “I didn’t have to buy one drop of insecticide.”
Domingos belongs to a growing group of farmers who are reluctant to use chemical pesticides to protect their crops.* Instead, they use methods that do away with or, at least, reduce the use of chemicals. “What kind of methods?” I asked Sandro Müller, an agronomist who has been conducting some experiments at a citrus plantation near São Paulo. “Why does it make sense for farmers to hold back on the use of the insecticide duster in the first place?”
The Pesticide Cycle
To help me visualize one dark side of the use of chemical insecticides, Sandro says: “Imagine a group of police officers chasing a bunch of bank robbers. To get away, the robbers dash into a busy office building. With the robbers lost in the crowd, the police call in a helicopter that drops a gas bomb on the office complex. This kills not only the robbers but also innocent office workers and the building’s security guards. Something like this happens when a farmer bombards his crop repeatedly with potent insecticides. They kill harmful insects, the robbers, but they also knock out useful ones, the security guards.”
“But at least the crop has been saved,” I reply. Yet Sandro points out that pesticides used indiscriminately start a harmful cycle. How so? Some bugs survive the spraying because they are resistant to certain pesticides. Afterward they find themselves sitting in the middle of a crop free from all ‘security guards,’ or useful insects—courtesy of the farmer’s spraying.
Plenty of food and the lack of natural enemies guarantee a rapid increase in the insecticide-resistant bug population, which forces the farmer to spray again, perhaps resorting to an even more potent type of insecticide. In some bean-growing areas in South America, farmers spray every week. The end result of this cycle? “If you sow pesticides,” said one farmer, “you reap poison.”
Pesticide Use—A Lesser Evil?
Research shows that the man who is poisoning pests is also poisoning himself. In Brazil alone, reported the magazine Guia Rural, pesticides poison some 700,000 people each year—that is an average of one person every 45 seconds! And the World Health Organization reports that worldwide 220,000 people die each year from exposure to toxic pesticides. Besides, pesticides are doing great harm to our environment.
Though some people today feel that opening a pesticide container is much like opening Pandora’s box, using pesticides is often seen by others as the lesser of two evils. This is how the argument goes: It is either pesticides and food or no pesticides and hunger. After all, the number of people on earth is growing while the amount of land fit for farming is shrinking. If global starvation is to be prevented, crops have to be protected against harmful insects that are capable of destroying them.
Clearly, pests constitute a major problem. Fortunately, though, a growing number of farmers around the world are learning that there is an approach that is better than dusting crops with heavy doses of pesticides. It is called integrated pest management, or IPM.
“What is IPM?” I asked Professor Evôneo Berti Filho, who is head of the Entomology Department at the University of São Paulo in Piracicaba and a leading researcher in natural pest control. Professor Berti explained that the goal of IPM is to reduce insecticide use to the minimum necessary and to employ only those insecticides that kill specific harmful bugs. Restrained spraying is then augmented by natural forms of pest control.
One such form of pest control is crop rotation. For example, from year to year, a farmer may rotate crops of corn with beans. Bugs that love corn but do not care for beans either starve or move out in search of neighborhoods with more corn. Then, the next time corn is planted, most of the bugs may be gone—at least for a while. And by the time the corn-loving bugs return en masse, another crop rotation may soon force them to pack up again.
Biological control is another component of IPM. It consists of farmers recruiting as allies insects, bacteria, viruses, fungi, and other natural enemies of pests. For example, Brazilian researchers observed that in nature many caterpillars died after contracting a virus called baculovirus. They figured that since the virus is harmless to humans, they could spray crops with a liquid containing this virus and it would work as a biological insecticide against caterpillars feasting on soybean and cassava crops. It worked. Caterpillars died a few days after chewing the sprayed crops. As a bonus, the dead caterpillars also provide the farmer with free ammunition for future battles. How?
“The farmer simply puts the dead, infected caterpillars in a blender,” explained Professor Berti, “pulverizes them, filters the blended mass, and stores the resulting liquid in a freezer.” Then the farmer thaws the virus-infected liquid, mixes it with water, and sprays the mixture on his crop.
This biological insecticide may lack the swift punch of its chemical counterparts, yet it has, says one researcher, at least a 90-percent success rate.
Beating Bugs—The Natural Way
Recruiting useful insects as allies to combat harmful bugs is another important part of biological pest control. Yet, despite efforts to convince farmers to employ this form of bug control, many farmers in Brazil and elsewhere are still reluctant to do so. Why? It seems that the idea of purposely releasing insects on farmland makes about as much sense to farmers as releasing cockroaches in apartments would make to city dwellers. “To most farmers,” Professor Berti told me, “all insects are plant eaters. The last thing a farmer wants is more of them.”
Clearly, then, biological pest control will gain popularity only when farmers understand that some insects are their allies. For example, fruit growers in California, U.S.A., enlisted the help of ladybugs in the late 1800’s. At the time, harmful insects, accidentally imported from Australia, had attacked and virtually eliminated all lemon and orange trees. It took the ladybugs less than two years to get the insect invaders under control, saving California’s citrus groves!
Control That Makes a Difference
Today some farmers in Brazil are rediscovering the role of the joaninha (little Joanna, the name for the ladybug here) as a reliable ‘security guard.’ “Joaninhas combat plant lice in this citrus growth,” Sandro told me as we walked along rows of orange trees in the citrus plantation under his care. He stopped at an orange tree, reached for a twig with young leaves, and bent it down. Aphids, or plant lice—sluggish insects the size of a pinhead—sat motionless with their beaks anchored in the leaves, sucking sap.
These lice, though, are food for the ‘security guard.’ In fact, among some types of ladybugs, one individual bug may munch on 800 lice during its life span. Is that enough to make a difference? “It is,” said Sandro, “if you leave enough grass and weeds between the citrus trees to provide a home for plenty of ladybugs and other natural enemies.” In the past, when biological control was not practiced in this orchard, noted Sandro, chemical insecticides were sprayed every two weeks. Today, thanks to natural enemies like the ladybugs and other insects, the need to spray insecticides has dropped to every two or three months.
The ladybug is only one of many natural allies that farmers count on. Bees, wasps, birds, spiders, frogs, toads, to name a few, are all members of the round-the-clock pest-control army. Even fish help to replace the spray can. How?
In China, reports researcher Xiao Fan, of the Department of Agriculture and Forestry in Nanking, Kiangsu Province, the need for insecticides was reduced when fish began to be raised in flooded rice fields. Farmers pull a rope over the plants so that the insects drop into the water. “Because the planthoppers pretend to be dead when they fall from the rice plants,” explains Fan, “they are easily eaten by the fish.”
Using less pesticide also allows useful insects to survive. These insects join forces with the bug-eating fish in fighting pests. Thanks to biological pest control, says Fan, the use of large amounts of poisonous insecticides is a thing of the past. The health and ecological benefits, he adds, are obvious.
Granted, farmers are embracing IPM more for economy than for ecology. After all, cutting down on expensive pesticides saves money, and that means greater profits—an incentive with a timeless and global appeal. Nevertheless, if more economic profits also lead to less poisoned crops and less environmental damage, then IPM brings benefits to farmers and consumers as well as the ecology. As one observer put it, with IPM “everybody wins.”
The most widely used types of pesticides are (1) insecticides, (2) herbicides, (3) fungicides, and (4) rodenticides. Each type is named after the pest it controls.
[Box on page 21]
Even if integrated pest management were practiced by all farmers worldwide starting today, the pesticide problem would be far from over. The United Nations Food and Agricultural Organization (FAO) estimates that there are more than 100,000 tons of leftover pesticides stored in developing countries. “A significant part of the stocks,” notes Our Planet, a magazine published by the United Nations Environment Programme, “are left-overs of pesticides obtained under aid agreements.” These supplies include large amounts of DDT and other pesticides that are now regarded as hazardous waste. If this pesticide heritage is not removed, comments Our Planet, “disasters can be expected.”
Cleaning up, though, is a costly business. Removing the pesticide heritage in Africa alone may cost up to $100 million. Who will foot the bill? The FAO calls upon the donor lands to help do so. Yet, as the FAO points out, “assistance should also be sought from agrochemical companies, which often played a role in excessive or unnecessary pesticide supplies.” So far, though, these companies have remained “reluctant to make financial contributions towards the clean-up of old stocks.”
[Box on page 22]
Modified Plants—Why Controversial?
Biotechnology is another weapon in the fight against pests. With man’s growing knowledge about the inner workings of the DNA molecule, researchers have been able to combine DNA fragments of different species and develop plants that come with built-in defense mechanisms against pests.
Corn is one example. Genetic engineers transferred a gene from another source into the DNA of corn. The introduced gene, in turn, produced a protein that proved to be deadly for pests. The result is a genetically manipulated corn plant that holds its ground against its insect enemies.
Nevertheless, engineered plants are controversial. Opponents argue that they may make people ill or that modified crops could become thriving weeds. Some scientists warn that plants equipped with an insect-killing gene will hasten resistance in pests. “We should temper our enthusiasm about genetic engineering,” cautions entomologist Berti. “Remember how thrilled people were in the 1950’s when insecticides were hailed as miracles? Today we know better. Miracle insecticides have given rise to miracle insects. Who knows what problems today’s engineered miracle plants will cause?”
Even if all biological problems can be solved, some people have moral concerns about scientists’ meddling with genetic codes. Some feel that biotechnology may resolve old pesticide problems but leave us with new ethical problems instead.
[Picture on page 23]
A ladybug may eat hundreds of pests