Genetically Modified Cotton: Much Higher Yields

Genetically modified (GM) pest-resistant cotton may provide yields up to 80 per cent higher than traditional types. This has been observed by scientists from the University of Bonn and the University of California at Berkeley in field trials in India. Their conclusion: peasants in the tropics and sub-tropics can benefit substantially from GM plants. These findings are surprising, since it has hitherto only been possible to detect very minor increases in yield, if any, in similar studies in temperate climate zones such as the US and China. The researchers are publishing their results in the forthcoming issue of the prestigious journal Science (Vol. 299, No. 5608) on 7th February.

The enemy is small, but greedy: the bollworm destroys a large part of the world’s cotton crop every year; farmers spray insecticide up to 20 times a year to combat this most important cotton pest. In 1997, therefore, Monsanto launched a type of cotton on the market which is largely resistant to this pest: Monsanto scientists had introduced a bacterial gene into the plant which contains the blueprint for a very specific insect poison. What is known as Bt cotton (Bt stands for the gene donor Bacillus thuringiensis) produces its insecticide itself, so to speak.

On more than one third of China’s total cotton-growing area this GM type is being grown; the use of pesticides has been reduced by over 70 per cent. Pesticide pollution, which used to be the norm, has been greatly reduced. However, the yield only increased by a maximum of 10 per cent; in GM soya beans scientists have sometimes even noticed slight reductions in yield. However, the ’pressure from pests’ in the US or China, where the studies have been taking place up to now, is considerably less than in the tropics and sub-tropics. Also, chemical pesticides are less affordable to farmers in those poorer countries. For example: whereas in the US insects only destroy about 12 per cent of cotton production annually, the losses in India’s small farm sector amount to 50 to 60 per cent. Dr. Matin Qaim of the University of Bonn’s Centre for Development Research (Zentrum für Entwicklungsforschung, the ZEF) has therefore been investigating the success of Bt cotton in India together with Professor David Zilberman from Berkeley.

In 2001, a successful field trial was started, involving 395 farms from seven Indian states. In three adjacent fields the farmers were to plant Bt cotton, the same sort without the resistant gene and a third type which is a popular local hybrid. The use of insecticide for the Bt cotton was on average 70 per cent less than for the two other types; however, the yield was more than 80 per cent higher. ’Despite the higher costs for the seeds, the farmers were able to increase their income five-fold with the GM type. Admittedly, infestation with bollworm was particularly high in 2001,’ Dr. Qaim cautions. ’In preliminary studies with fewer farmers between 1998 and 2001 we were able to detect an average increase in yield of 60 per cent.’

The Bt cotton findings are basically also applicable to food plants. Particularly regions in the tropics and sub-tropics, which are under severe pressure from pests could benefit from GM plants with increased pest resistance, the scientists conclude. ’We expect the biggest increases in yields to take place in South and South-East Asia and in Central and Southern Africa, i.e. precisely in those areas with the highest population growth, which are especially dependent on increasing yields.’ Even so, Qaim argues in favour of taking the potential risks of ’green genetic technology’ seriously. ’In all the previous studies Bt cotton has been proved to be harmless to humans and the environment; however, we should test each new application on its individual merits.’ He recommends that the production of GM seeds should not simply be left to the big companies, since the dependence of developing countries on the developed nations would then increase further. However, in his view this problem cannot be laid at the feet of gene technology: ’It is in our hands to create the general conditions which enable this promising technology to be made available to the poor at affordable prices.’