BAR TODAY || Official Quarterly Publication of the Bureau of Agricultural Research

Archives (2003)

Between the Bt corn rows
by Junelyn dela Rosa

April-June 2003
Volume 5 No. 2

Bt corn

The debate over Bacillus thuringiensis (Bt) corn is gathering more heat as a series of events added more wood to an already growing. This blaze is fanned by the commercialization of Bt corn, first Bt corn harvests in April, the month-long hunger strike, the numerous rallies by environmental activists and farmer groups, the media's bipolar convictions, the government's diplomatic dismissive, and the sermons by the clergy.

While most of us stay in the sidelines on this issue, we cannot afford to stay long there since sooner or later we will be part of the action as consumers of products- GM-free or not. Let us review some of the most important issues surrounding the controversial Bt corn.

Food safety
How safe is Bt corn? Would my family and I be at risk if we eat Bt corn? What is in Bt corn? How was it made and how does it work? Are Bt corn products less safe than normal corn? We need to ask these questions in order to decide whether anti-Bt corn groups are right in calling Bt corn- Frankenstein food or poison food.

The controversy about Bt corn stems from the fact that it has been added with a certain gene from Bacillus thuringiensis- a rod-shaped bacterium that occurs naturally in soils worldwide. This gene produces a protein called Cry protein that is lethal to corn borers, hence making the corn plant resistant to corn-borer attacks.

This protein is lethal to corn borers because they have a strong alkaline digestive tract (in contrast, humans and other animals have acidic digestive tracts) that dissolve the crystals that contain the proteins thereby releasing the proteins. These proteins disrupt the lining of the caterpillar's gut causing the caterpillar to starve and die eventually.

While Bt corn is still debated among Filipinos, it would be wrong to say that we have not yet eaten GM products as Philippines imports corn and corn products from developed countries where Bt crops have already been commercialized since 1985. In the United States, for instance, at least 70% of their food products contain ingredients from GM crops.

The Department of Agriculture (DA) and the National Committee on Biosafety of the Philippines have been tasked to assess and monitor the field tests of Bt corn. Both have said that Yieldguard 818, Monsanto's approved corn variety has undergone strict testing and evaluation since 1996 before it was granted permit last December. Yieldguard 818 has the strain designed to kill the Asiatic corn borer which can cause up to 80% yield loss.

However, opponents to the technology are still challenging the testing process and are calling on President Gloria Macapagal-Arroyo to issue a moratorium and withdraw the commercialization of Bt corn.

Bt corn's impact to the environment
Another issue is whether Bt corn is good or bad for the environment. Anti-GMO groups have fed the public's fear and doubts by saying that Bt corn which they call "Frankenstein food" will spawn mutant insects that will bring in the next apocalypse. While that is perhaps a result of watching too many sci-fi movies, it is important to ask two questions:

Will Bt corn cause resistance in target species?
Most scientists agree that there is potential for corn borer resistance to Bt corn but it is remote. Dr. Michael Cohen, IRRI entomologist, discussed the "refuge/high-dose" strategy and Bt plants that have two Bt toxins- both practical steps to sustain the Bt technology in the field.

He said that the refuge strategy involves maintaining "refuges" in the fields. Refuges are non-Bt crop plants that will maintain the population of Bt susceptible insects. "Refuges" can be fields of non-Bt plants or of non-Bt plants within fields. When the susceptible insects mate with the resistant insects, the offspring are usually susceptible. These insects will be killed if the Bt cultivars have a high dose of toxin. Therefore, the combination of refuges plus plants with a high dose of toxin can keep the population of resistant insects at extremely low numbers.

In the USA, the government has enforced the "refuge" system in the countryside. Farmers who plant Bt crops must allot 4-20% of their land to non-Bt crops and these refuge fields must be within approximately one kilometer of their Bt fields.

Here in the Philippines where the average landholding is less than a hectare, "refuges" should be planned and maintained by the community. The field of farmers who choose to grow non-Bt cultivars would also serve as refuges for their neighbors. The government should help maintain seed supplies of non-Bt cultivars.

Dr. Cohen explained that concerns on stemborer damage to likely increase in non-Bt fields is misplaced since moths could not detect whether the plant is Bt or non-Bt. "It is very likely that stemborer population in non-Bt fields will more likely decline than increase after introduction of Bt rice", he said.

Another strategy is to plant Bt rice cultivars containing two Bt toxins. Dr. Cohen said insects that are resistant to cultivars that contain two high-dose toxins will be extremely rare. And since resistant insects will be very rare then fewer susceptible insects will be needed to ensure that resistant insects do not mate with each other. Thus, smaller and fewer refuge fields are necessary to maintain the effectiveness of Bt plants.

Will Bt corn harm or kill non-target species?
This issue took center stage when scientific journal- Nature published an article saying that Bt corn pollen was found toxic to the larva of the Monarch butterfly. In a conference, entomologists concluded that 1) Bt corn pollen does have some toxicity to Monarch larvae, 2) toxic levels of corn pollen do not occur far from corn fields, and 3) it is likely the Bt corn pollen is not a significant mortality factor to Monarch butterfly larva. Thus the Monarch butterfly issue was probably overblown in the press but there do appeared to be some effects of the pollen on off target organisms.

Monsanto's monopoly of the technology
Does the country want its corn industry and food security controlled by foreign companies, such as Monsanto that now propagates the Bt corn? Most anti-groups have strongly opposed Bt corn by underlining the ills of a foreign-owned technology. They argue that with the large overhead Monsanto incurred in developing the technology, naturally it would want to make as much profit now that its Yieldguard 818 has been approved for commercialization. This would mean farmers will not necessarily be better off even with the expected higher yields since they would have to pay more for the seeds and other inputs.

There are many other issues in the Bt corn debate. Do we need to label commercial corn even if the product only contains 1% Bt corn? If we ban Bt corn now are we sacrificing what could be one of the best agricultural innovations in the 21st century? These are legitimate questions which we need to answer to make wise decisions later on. While most of us are still waiting in the sidelines on this issue, sooner or later we will have to make decisions when Bt corn products reach our local market. While debates will likely never be resolved, further research and testing may reveal whether the advantages and benefits of this technology outweigh its risks. One thing is certain: Bt corn has made its imprint on people from all walks of life and like other GMO crops will continue to play a critical role in bringing food to tables all over the world.

Sources:
1)Bt rice: Practical steps to sustainable use by Dr. Michael Cohen, 2002 Entomology and Plant Pathology Division, International Rice Research Institute; F. Gould, Department of Entomology, North Carolina State University and J.S. Bentur, Department of Entomology, Directorate of Rice Research, India E-mail: m.cohen@cgiar.org
2) The Philippines will harvest first Bt corn in April by R. Sarmiento SEARCA Biotech News Updates March 18, 2003