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Interested
parties should note that the Greenpeace/FOE report does not accurately
reflect mainstream commercial experience of using Bt maize by Spanish farmers.
The primary
‘claim’ in the report about the impact of using Bt technology on maize
yields is that ‘there are no clear advantages of using Bt maize’ and that
‘some other non GM varieties give better yields’.
Although both of these statements are correct, within clearly defined
and specific circumstances, neither statement is representative of the
experiences of the majority of Bt maize farmers in Spain: Ø
The Greenpeace/FOE report evidence cited is based on small-scale crop
trial data only, from one location in the region of Navarra. It does not include commercial farmers and does not consider
data from a number of regions. The
area planted to maize in Navarra is also very small relative to mainstream
production regions (it accounts for about 3%-4% of the total Spanish maize
area); Ø
The location where the Navarra trials data is taken from generally
suffers low incidence and frequency of corn borer problems.
Therefore it is not surprising that Bt crops trialed with conventional
crops did not offer a clear yield advantage. This variability in impact of Bt technology was documented in
the Brookes report, which highlighted a clear link between Bt’s impact on
yield and the level of corn borer problems suffered by individual farmers; Ø
It is possible for conventional maize varieties to deliver higher yields
than the Bt variety used in trials because many different factors determine
yield in a particular variety. These
include the ability of the variety to adapt to the local growing conditions,
moisture and temperature levels, soil conditions and use of inputs like
fertilisers and crop protection products. The
presence, or absence, of the genetic modification for insect control is only one
factor of influence. Evidence
presented in the Brookes report was based on real, farm level data over a four
year period (data from the equivalent of about 500 farms who plant about 15,000
hectares of maize, of which about 3,000-4,000 hectares were Bt maize).
It included farms in locations with high and low levels of corn borer
problems and highlighted that the damage that corn borer can cause to yield
varies by location, year, climatic factors, timing of planting, whether
insecticides are used or not and timing of insecticide applications.
Hence the positive impact on yields of planting Bt maize varies.
In regions where high infestation levels are commonplace the benefit is
an average 10% yield improvement where insecticide treatments were previously
used and, 15% where insecticide treatments were not previously used.
Other research across a number of Spanish regions put the average yield
improvement at an average of 6.3% (within a range of 2.9% to 12.9%) whilst in
some areas of low/medium pest attack the average yield improvement over the last
four years has been about 1%. Overall, the
farm level evidence available shows that the use of Bt maize meets the needs of,
and provides benefits to, farmers in regions that suffer high/medium levels of
corn borer infestation. For further
information contact Graham Brookes on 00 44 1303 840958 2 September
2003 |
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