China Pest Surges On Bt Cotton
17 May 2010 BEIJING, China — A fifteen-year study in northern China by scientists from the Chinese Academy of Agricultural Sciences and the China National Agro-Technical Extension and Service Center, which surveyed nearly three million hectares (ha) of Bacillus thuringiensis (Bt) cotton and 26 million ha of other crops, shows that the rise of the mirid bug (Heteroptera Miridae) directly relates to the increased planting of Bt cotton, reports SciDev.net. The pest is spreading out from Bt cotton fields and destroying fruit, vegetable and cereal crops.
In the study, insecticide use on cotton farms was followed for 15 years. Five years into the study, scientists also began to audit mirid bug numbers at 38 locations. Consistent with the planting of genetically modified (GM) Bt cotton, the bugs began to spread from cotton fields to fruit farms — changing status from a minor pest to a major one. To blame, according to the scientists, is the lack of pesticides. The sprays previously used to kill cotton bollworm (Helicoverpa armigera) also controlled mirid bugs. Different insecticides are now being used to kill the growing number of mirid bugs.
The scientists are urging more comprehensive risk assessments for GM crops and their effect on secondary pests. Ninety-five percent of cotton planted in northern China is Bt cotton.
“Our work shows that a drop in insecticide use in Bt cotton fields leads to a reversal of the ecological role of cotton; from being a sink for mirid bugs in conventional systems to an actual source for these pests in Bt cotton growing systems,” wrote the authors in their paper, which was published May 13 in the journal Science.
Get The Newsletter Today!
