Up to 35 percent of the losses in annual crop production worldwide are due to pests, according to the Rome-based UN Food and Agriculture Organization (FAO). Of the estimated one million insects in the world, some 180 species frequently cause serious damage to crops.
Any material used to kill pests is called a pesticide, and usually any organism that competes with humans for food, fiber, or living space is called a pest. The use of chemicals to kill pests is not a new idea. For centuries, farmers have used minerals such as arsenic, lead, and mercury or natural plant substances to kill insects and other pests.
For a long time, no one seemed to question the safety of pesticides. Not until 1962, when marine biologists and writer Rachel Carson wrote the now classic Silent Spring. In her book, she described how pesticides cause long-term hazards to birds, fish, other wildlife, and humans, but provides only short-term gains to controlling the pests.
“Pesticides are like bombs being dropped in the food web creating enormous destruction,” said Dr. K. L. Heong, an entomologist who once worked with the Laguna-based International Rice Research Institute.
Pesticides also pose health risks to people who are exposed to them. “There is direct evidence from clinical and epidemiological studies of humans who are occupationally or accidentally exposed to pesticides that normal immune system structure and functions are altered,” reports the Washington-D.C.-based World Resources Institute.
It is for this reason that scientists are constantly looking for alternative ways of dealing with plant pests. And this where Bt comes in. Bt stands for Bacillus thuringiensis, a common soil bacterium so-called because it was first isolated in the Thuringia region of Germany.
“Bt produces a protein that paralyzes the larvae of some harmful insects, including the cotton bollworm and the Asian and European corn borers, all of which are common plant pests whose infestations produce devastating effects on important crops,” notes a briefing paper circulated by the International Service for the Acquisition of Agri-biotech Applications (ISAAA).
How does Bt acts? “When ingested by the larva of the target insect, the Bt protein is activated in the gut’s alkaline condition and punctures the mid-gut leaving the insect unable to eat,” the briefing paper explains. “The insect dies within a few days.”
Bt’s ability to produce the insecticidal protein has paved way for several studies to exploit the organism’s agronomic value. So far, more than 200 types of Bt proteins have been identified with varying degrees of toxicity to some insects.
In the past, Bt was cultured by fermentation. It has been used as an insecticide by farmers around the world for over 40 years now. In fact, organic farming has benefited by Bt insecticides as it is one of the very few pesticides permitted by organic standards.
As an insecticide, Bt is applied either as a spray or as ground applications. It comes in both granules and liquefied form. “The efficiency of both applications is quite limited, as target organisms often do not come in contact with the insecticide as they are found on the underside of the leaves or have already penetrated into the plant,” the briefing paper states.
Scientists are working to overcome this problem through the use of modern biotechnology. What they do is take the Bt gene from the bacterium and incorporate it into the genome of plants. “Thus, these plants have a built-in mechanism of protection against targeted pests,” the briefing paper says. “The protein produced by the plants does not get washed away, nor is it destroyed by sunlight. The plant is thus protected from the bollworm or the corn borer round the clock regardless of the situation.”
Among the crops where Bt was incorporated include cotton, corn, poplar, potato, rice, soybean, and tomato. Recently, Bt has been introduced in eggplants, one of the most often-used fruit vegetables in the Philippines.
However, it is often attacked by eggplant fruit and shoot borer (EFSB), which is considered as the most destructive insect pest. “The EFSB can cause as much as 50-75 percent loss of fruits,” said former Science Secretary Emil Q. Javier, who is the president of the National Academy of Science and Technology. “The worm of the insect bore tunnels in the fruit, rendering them unfit for consumption.”
Unfortunately, there is no known genetic resistance to EFSB in cultivated and wild eggplants. “The insects are concealed in the shoots and fruits and are difficult to reach,” Dr. Javier explained. “Thus in order to protect their crops, farmers spray their plants almost every other day with insecticides.”
The current methods used by some eggplant growers in controlling the fruit and shoot borer are unacceptable, said Dr. Emiliana Bernardo, an entomologist and retired professor of the University of the Philippines. Many eggplant farmers spray chemical insecticides every other day, or up to 80 times per growing season to control fruit and shoot borer infestation in their farms, she pointed out.
The practice is unacceptable and unhealthy to consumers, farmers and the environment. According to Dr. Bernardo, studies conducted in major eggplant producing provinces found that almost all farmers use chemical insecticides and that some even dip the unharvested eggplant fruits in a mix of chemicals just to ensure that harvests are marketable.
“The very basic question is, which is safer, the present practice or the alternative, the Bt eggplant which is rigorously evaluated by experts?” she asked. “Is bathing the unharvested eggplant fruits in chemicals, which would end up in dinner tables of people, safe?”
But despite this, there are those who are oppose with Bt eggplant. “We are not anti-GMO. We are not anti-development or anti-technology,” Daniel Ocampo, sustainable agriculture campaigner for Greenpeace Southeast Asia, was quoted as saying. Testing of GMOs (genetically-modified organisms), he added, “should be confined in the laboratory, not in the fields.”
Neal H. Cruz, in his Inquirer column, wondered: “Why is Greenpeace doing this when biotechnology can improve the lives not only of Filipinos but also of the peoples of other nations? Some people suspect that Greenpeace is secretly working for the big manufacturers of chemical pesticides who will lose their lucrative markets if pest-resistant crops are propagated through biotechnology.”