Farm-scale evaluation of the impacts of transgenic cotton on biodiversity, pesticide use, and yield

doi:10.1073/pnas.0508312103

Farm-scale evaluation of the impacts of transgenic cotton on biodiversity, pesticide use, and yield

*Department of Entomology, University of Arizona, 410 Forbes Building, P.O. Box 210036, Tucson, AZ 85721-0036;
^†Graduate Interdisciplinary Program in Insect Science, University of Arizona, 225 Life Sciences South, Tucson, AZ 85721;
^‡Arizona Remote Sensing Center, Office of Arid Lands Studies, University of Arizona, 1955 East Sixth Street, Tucson, AZ 85710;
^§Arizona Research and Protection Council, 3721 East Weir Avenue, Phoenix, AZ 85040-2933; and
^¶Department of Plant Science, Macdonald Campus, Raymond Building, McGill University, St-Anne-de-Bellevue, QC, Canada H9X 3V9

Edited by May R. Berenbaum, University of Illinois at Urbana-Champaign, Urbana, IL, and approved April 6, 2006 (received for review September 22, 2005)

Abstract

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.

Footnotes

^‖To whom correspondence should be addressed. E-mail: ycarrier{at}ag.arizona.edu
Author contributions: B.J.O., S.E.M., and Y.C. designed research; M.G.C., C.Y., C.S., C.-y.H., M.R., C.O., C.E.-K., L.A., and Y.C. performed research; M.G.C., C.-y.H., M.R., C.E.-K., B.J.O., S.E.M., P.D., and Y.C. analyzed data; and Y.C. wrote the paper.
Conflict of interest statement: No conflicts declared.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations:

Abbreviations:

Bt,

Bacillus thuringiensis;

BtHr,

Bt protein and herbicide resistance;

nonTr,

nontransgenic;

IGR,

insect growth regulator;

ha,

hectare;

NDVI,

Normalized Difference Vegetation Index.
Freely available online through the PNAS open access option.