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[SANET-MG] Bt cotton does not imporve yield
In the article below Bt is Cry1Ac for pink boll worm control and BtHr
is Bt roundup ready cotton.
Published online before print May 4, 2006
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0508312103
Farm-scale evaluation of the impacts of transgenic cotton on
biodiversity, pesticide use, and yield
( agricultural sustainability | environmental impact | transgenic crops )
Manda G. Cattaneo *, Christine Yafuso *, Chris Schmidt *, Cho-ying Huang
, Magfurar Rahman , Carl Olson *, Christa Ellers-Kirk *, Barron J. Orr ,
Stuart E. Marsh , Larry Antilla , Pierre Dutilleul ¶, and Yves Carrière *||
Higher yields and reduced pesticide impacts are needed to mitigate the
effects of agricultural intensification. A 2-year farm-scale evaluation
of 81 commercial fields in Arizona show that use of transgenic Bacillus
thuringiensis (Bt) cotton reduced insecticide use, whereas transgenic
cotton with Bt protein and herbicide resistance (BtHr) did not affect
herbicide use. Transgenic cotton had higher yield than nontransgenic
cotton for any given number of insecticide applications. However,
nontransgenic, Bt and BtHr cotton had similar yields overall, largely
because higher insecticide use with nontransgenic cotton improved
control of key pests. Unlike Bt and BtHr cotton, insecticides reduced
the diversity of nontarget insects. Several other agronomic and
ecological factors also affected biodiversity. Nevertheless, pairwise
comparisons of diversity of nontarget insects in cotton fields with
diversity in adjacent noncultivated sites revealed similar effects of
cultivation of transgenic and nontransgenic cotton on biodiversity. The
results indicate that impacts of agricultural intensification can be
reduced when replacement of broad-spectrum insecticides by
narrow-spectrum Bt crops does not reduce control of pests not affected
by Bt crops.
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