April 2, 2003

Matin Qaim and David Zilberman
Reprinted from ISB News Report April 2003

Hitherto applications of genetically modified (GM) crops in the United States, China, and Argentina
have led to significant reductions in the use of chemical pesticides, but, in most cases, yield increases
have been rather small. Although pesticide savings bring about important economic and
environmental gains, it has often been argued that GM crops have little to offer to the poorest
countries where local agricultural output needs to be increased on a limited amount of farmland. We
argue that this generalization based on partial data is false. By using the example of Bt cotton in India,
we suggest that currently-existing GM crops can have significant yield effects, which are most likely
to occur in the developing world, especially in the tropics and sub-tropics. The evidence in India
supports a general principle that a pest-control strategy, in this case biotechnology, has a strong yield
effect in locations where pest damage is substantial and use of alternative control agents is
constrained.

Bt cotton provides a fairly high degree of resistance to the American bollworm (Helicoverpa
armigera), the major insect pest in India. The technology was developed by Monsanto and was
introduced into several Indian hybrids in collaboration with the Maharashtra Hybrid Seed Company.
Field trials with these Bt hybrids have been carried out since 1997 and, for the 2002/03 growing
season, the technology was commercially approved by the Indian authorities. Its performance during
the first commercial season in India is hotly disputed among biotechnology advocates and opponents,
but an independent scientific assessment has not been conducted thus far.

For our analysis, we used data from on-farm field trials that were carried out during the 2001/02
growing season as part of the regulatory procedure. On 157 farms in three different states, Bt cotton
hybrids were planted next to an isogenic line without the Bt gene and a local hybrid commonly grown
in the particular district. All three plots were managed by the farmers themselves, following
customary practices. Apart from official data that were collected by local researchers for biosafety
evaluation, we used our own questionnaire to obtain details on input-output relationships from
participating farmers.

While there was no significant difference in the number of sprays against sucking pests, Bt hybrids
were sprayed three times less often against bollworms than the conventional hybrids. On average,
insecticide amounts on Bt cotton plots were reduced by almost 70%, which is consistent with studies
from other countries. The difference in India, however, is that use of Bt cotton also leads to a
significant yield effect. During the field trials, average yields of Bt hybrids exceeded those of non-Bt
counterparts and local checks by 80% and 87%, respectively.

Bt is a pest-control technology, so rather than an increase in the genetic yield potential, these effects
have to be interpreted as avoided crop losses. Figure 1 confirms that, under Indian conditions,
bollworms have a high destructive capacity which is not well controlled in conventional cotton. At
average pesticide amounts of 1.6 kg/ha (active ingredients) on the conventional trial plots, crop
damage in 2001/02 was about 60%. Bt does not completely eliminate pest-related yield losses. Yet,
to achieve the same level of damage control without the technology would require a triplication of
currently used pesticide quantities.

2001/02 was a season with high bollworm pressure in India, so that average yield effects will be
somewhat lower in years with fewer pest problems. Moreover, although the trials were managed by
farmers, experimental results cannot simply be extrapolated to commercial agriculture. But even
when discounting for these aspects, yield advantages of Bt cotton will remain bigger in India than in
the United States or China.

Analysis of factors influencing yield impacts of new, effective pest control technologies suggests that
they depend on local pest pressure, availability of alternatives for pest control, and farmers' adoption
of these alternatives. Generally, pest pressure in tropical and sub-tropical regions is higher than in
temperate zones, while pesticide-use intensities are much lower, due to technical and economic
constraints. In India, pesticides are available on local markets, but their effectiveness is limited
because bollworms have developed resistance to many of the common products. Furthermore,
small-scale cotton producers are often credit-constrained and do not have access to chemicals at the
right point in time.

Given these linkages, we have a theoretical base to suggest that the case of Bt cotton in India might
be more representative of GM crop impacts in developing countries than previous examples. Almost
all GM crop technologies were initiated by commercial firms in the industrialized world, targeting the
needs of farmers who are able to pay for them. Some varieties were transferred to the commercial
sectors of Latin America and China, where agroecological conditions and pesticide application rates
are similar. In all cases, yield effects have been low to medium, while there have been significant gains
from pesticide substitution.

However, with careful adaptation and effective regulation, these same technologies can also be
introduced to other developing-country regions, where yield effects will be more pronounced.
Pest-resistant GM crops are easy to manage at the farm level, and they could substantially reduce
current gaps between attainable and actual yields, especially in smallholder farming systems.
Preliminary evidence from Indonesia and South Africa is in line with this hypothesis. Agricultural
biotechnology offers many more applications for developing countries beyond pest control, but we
show that the GM crops developed thus far can already have significant impacts. It is a major policy
challenge to invest more in public research and address the existing institutional constraints, so that
promising biotechnologies can reach the poor at affordable prices on a larger scale.

Reference

Qaim M and Zilberman D. 2003. Yield effects of genetically modified crops in developing countries.
Science 299: 900-902.