Farmers’ survey

Spain: experience of Bt maize

So far Bt maize is the only genetically modified plant approved for cultivation in Europe. Large quantities of this maize are grown in Spain in particular – in 2007 it accounted for around 17 per cent of Spain’s total maize growing area. Now for the first time farmers’ experiences of Bt maize have been recorded in a survey published in the journal Nature Biotechnology.

Male inflorescence

Bt maize produces a protein which is toxic to its pest, the European corn borer

Maize yields in three Spanish provinces in 2004. Only in Zaragoza/Aragon were Bt maize yields significantly higher than those of conventional maize.

Number of insecticide applications in conventional maize (0.86 per year on average)

Number of insecticide applications in Bt maize (0.32 per year on average)

Bt maize with built-in resistance to the European corn borer, a major maize pest, has been grown in Spain since 1998. Consequently, Spanish farmers now have nine years’ experience of growing Bt maize commercially. In 2007 around 75,000 hectares of land was planted with the MON810 strain of Bt maize. In regions heavily infested with the European corn borer, transgenic maize accounts for up to 60 percent of the maize growing area.

The survey covered 195 farmers who grow Bt maize and 184 conventional maize growers. They were asked to provide information about yields, seed costs, maize prices obtained and use and costs of insecticides from 2002 to 2004.

Researchers at the University of Cordoba were among those conducting the survey in the three main Bt maize growing areas, the provinces of Zaragoza in Aragon, Lleida in Catalonia and Albacete in Castile-La Mancha.

To rule out the possibility that variations in yield could be attributed to varying levels of expertise amongst the farmers, for example, socio-economic profiles of the farmers were also compiled. This showed that the two groups (Bt maize growers and conventional farmers) were comparable. There were no statistically significant differences in their property circumstances, size of farms, main crop grown, age, education or experience of maize cultivation.

Higher yields with Bt maize during severe corn borer infestation

In the three years from 2002 to 2004, the farmers who grew Bt maize obtained higher average yields than the farmers who grew conventional maize. However, higher yields of statistical significance (11.8%) were recorded only in Aragon. According to the authors of the study, even though no data was available on European corn borer infestation and the resulting damage for these regions during the period of investigation, there were nonetheless indications of a more severe corn borer infestation in Aragon.

Regional variations in the yield increases could also be attributed to a lack of suitable Bt maize varieties for the particular regional conditions. In 2003 only two Bt maize varieties were commercially available in Spain, and yet by 2006 there were more than forty. But the most likely explanation for the slight variations is pest pressure, which varies from year to year.

The yield increases also resulted in direct increases in the incomes of the farmers growing Bt maize, since the farmers obtain the same price for fodder maize regardless of whether it is transgenic or not (0.13 euros per kilogram). Conventional maize was not able to command a higher price than Bt maize during the years of study.

Fewer insecticide applications with Bt maize

However, there were differences in insecticide and seed costs.

  • Insecticide use: the European corn borer can be controlled using conventional insecticides only during a limited time frame – between when the larvae hatch and when they start to bore into the stems. Nonetheless, spraying is sometimes carried out outside this period. In conventional maize cultivation an average of 0.86 insecticide treatments per year were carried out, but only 0.32 on Bt maize fields. No insecticide was used on 70 percent of the Bt maize fields. Likewise, 42 percent of the conventional fields were farmed without the use of insecticides.
  • Seed costs: only in Aragon, where the majority of Bt maize is grown and the highest yields were obtained, did farmers have to pay a significant premium for Bt seed compared with conventional seed.

On balance, farmers in Aragon earned up to 122 euros per hectare more per year once insecticide and seed costs had been deducted. In other regions profits were only marginal and the incentive to grow Bt maize was probably lower as a result.

The farmers were also asked to give reasons why they do or do not grow Bt maize. The most frequently cited reasons were:

  • reduced risk of losses as a result of corn borer damage
  • higher yield
  • better quality of harvest

The use of Bt varieties was associated with less damage to the plants, reduced sensitivity to fungal attack after harvest and a corresponding reduction in mycotoxin contamination.

The commonest reason given by conventional farmers for not switching to Bt maize was simply that they were reluctant to change.