Crop Biotech Update

Effects of Single and Stacked Bt Cotton on Honey Bee and Silkworm

September 18, 2013

In 2012, China grew 3.9 million hectares of insect resistant cotton which is about 80 percent of total cotton hectarage in the country. With this extensive use of the biotech crop, it is important to know its effects on non-target insects such as honey bee and silkworm, two economically important species in China. Thus, Lin Niu from Huazhong Agricultural University and other scientists conducted a study. They used the pollens from two Bt cotton cultivars (one expressing Cry1Ac/EPSPS and the other expressing Cry1Ac/Cry2Ab) to assess the effects of Bt cotton on adult honey bees and silkworm larvae.

Results of feeding studies showed no adverse effects of Bt cotton on the survival, cumulative consumption, and immune systems of honey bees with Bt cotton diet for one week. The same results were also obtained in the feeding experiment involving silkworm larvae. A significant difference in the total hemocyte count of some silkworm larvae was noted in conventional cotton and Bt cotton fed samples at highest pollen densities (~900 and 8000 grains/cm2) but this amount is too high to occur in natural conditions. Based on the findings, the single and stacked Bt cotton varieties studied do not cause any detrimental effects on adult honey bee and silkworm.

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