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Bt Cotton Helps Biocontrol: Observation over 20 years in China

Bt Cotton Helps Biocontrol: Observation over 20 years in China

In an article entitled, “Widespread adoption of Bt cotton and insecticide decrease promotes biocontrol services” published in 19th July issue of Nature, vol. 487, pp. 362-365, Yanhui Lu and 4 others.Over the past 20 years, vast plantings of transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have helped control several major insect pests and reduce the need for insecticide sprays. Because broad-spectrum insecticides kill arthropod natural enemies that provide biological control of pests, the decrease in use of insecticide sprays associated with Bt crops could enhance biocontrol services. However, this hypothesis has not been tested in terms of long-term landscape-level impacts. For a period over 20 years from 1990 to 2010 data were collected at 36 sites in six provinces of northern China. An examination of data reveals that there has been a marked increase in three types of arthropod predators, namely, ladybirds, lacewings and spiders as well as reduction in aphid pests. Decrease in frequency of these pests has led to extensive adoption of Bt cotton concomitant with reduced insecticide sprays in the cotton crop. Another benefit which these investigators discovered was that the insects predators having found no cotton plants to prey upon, tip out over from Bt cotton fields onto neighboring crops such as maize, peanut and soybean. Their work demonstrates that Bt crops instead of being harmful to the environment serve as a biological control by reducing the incidence of insect attack not only in cotton but insect damages to other crops which grow in areas adjoining cotton fields.

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