Agriculture problems - Cotton
Transgenic cotton: are there benefits for conservation?
Transgenic cotton has been cultivated worldwide for four years. In 1999 transgenic cotton was planted in only two (i.e. U.S. and China) of the six top cotton-producing countries with the U.S. as the leader.
Herbicide-tolerant cotton grown almost entirely in the U.S. was the most important transgenic trait with an approximate share of 55% of transgenic cotton in 1999 and very high adoption rates. Bt-cotton acreage has slightly decreased worldwide in favour of stacked varieties (i.e. herbicide-tolerant and insect-resistant). High adoption rates for herbicide-tolerant traits and substitution of insect-resistant crops by stacked varieties are common trends for all trans-genic crops.
Change in pesticide use
Current statistical data for the U.S. provided by the National Agricultural Statistics Service (NASS) reveal no correlation between transgenic cotton adoption rate and change in the overall amount of insecticides or herbicides.
From 1996 to 1998 the acreage of Bt-cotton steadily increased reaching 17% of the total cotton acreage in the U.S. in 1998, while insecticide use per acre remained more or less at the same level. However, according to the claims by agri-biotechnology firms, a decrease in insecticide use should have been expected. Data that will be published next year will give more information on this issue.
From 1997 to 1998 no substantial reduction in herbicide use for cotton farming occurred. Data on specific herbicides show a sub-stitution by glyphosate and bromoxynil, the corresponding herbicides to the herbicide-tolerant traits for other herbicides. Whether current herbicides are replaced by less harmful chemicals cannot be answered in this study.
Insects which are resistant to the Bt-toxin due to the widespread use of transgenic crops with the same Bt-toxin have not been reported in the field, yet. But from experience in develop-ment of insecticide resistance previously in the U.S. one can assume that resistance against the Bt-toxin is highly probable in the near future.
In the past, overuse of insecticides have led even to insecticide resistance to a broad spectrum of different insecticides at the same time. Furthermore, the incorporated Bt-toxin which is produced in the plant over the whole growing season is not sound with current integrated pest manage-ment (IPM) ideas in which pesticides are applied only on an economical threshold level.
Experience in transgenic cotton farming
Four years of cultivation of transgenic cotton is a short period for a proper environmental impact assessment, assuming that adaptation of new agricultural practices to transgenic cotton requires several years. Therefore, it stands to reason that current trends should be interpreted with caution.
But the most reliable data for the past two years provides little evidence that trans-genic cotton may contribute to a more sustainable and environmental-friendly cotton farming. It should be borne in mind that herbicide tolerance in com-bination with the interest to sell the corresponding herbicides can be inter-preted as the key-driving force for the adoption of transgenic cotton in the U.S.
In the near future, more statistical data provided by the National Agricultural Statistics Service (NASS) in the U.S. will help to assess the "environmental performance" of Bt and herbicide-tolerant cotton varieties. Field trials collected by the OECD will give an idea on what will be approved next: Major traits are multiple gene insect-resistance and tolerance to other herbicides.