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Submitted to: Proceedings of the California Conference on Biological Control
Publication Type: Proceedings Publication Acceptance Date: 7/14/2002 Publication Date: 9/1/2002 Citation: NARANJO, S.E. ARTHROPOD COMMUNITIES AND TRANSGENIC COTTON IN THE WESTERN USA. PROCEEDINGS OF CALIFORNIA CONFERENCE ON BIOLOGICAL CONTROL. 2002. pp. 33-38 Interpretive Summary: Since 1996, transgenic cotton expressing the insecticidal proteins of Bacillus thuringiensis (Bt) have been widely adopted by cotton producers throughout the USA to control caterpillar pests. In Arizona and southern California the main target pest has been the pink bollworm. A number of potential benefits and risks are associated with the use of transgenic crops in agricultural production systems. Among the benefits cited are reductions in broad-spectrum insecticide use, improved suppression of target pests, improved yields, reductions in production costs, and increased opportunities for biological control There are also potential risks, including outcrossing through pollen drift, horizontal transfer of transgenes to other organisms, food safety, loss of susceptibility to Bt toxins in target pests, and direct or indirect detrimental effects on non-target organisms. A 3 year study was completed to examine non-target effects of Bt cotton in Arizona with emphasis on the natural enemy complex. Replicated studies evaluated 3 criteria in paired Bt and non-Bt cotton plots; abundance and diversity of non-target organisms, and effects on natural enemy function. Results failed to demonstrate any consistent or statistically-significant changes in any of these criteria in Bt cotton. Technical Abstract: Transgenic cottons expressing the insecticidal proteins of Bacillus thuringiensis (Bt) have been widely adopted by cotton producers throughout the USA to control lepidopterous pests. Studies of the effects of Bt cotton on non-target organisms have been underway in Arizona since 1999. Here I provide a preliminary report of replicated field studies conducted from 1999 to 2001 to examine comparative effects of Bt cotton on natural enemy abundance, arthropod diversity, and natural enemy function. Analyses completed to date indicate that natural enemy abundance and overall arthropod diversity are affected by the use of additional insecticides for other pests, but not directly by transgenic cottons in comparison with non-transgenic cottons. Further studies suggest that natural enemy function, measured as rates of predation and parasitism on two key pests (Pectinophora gossypiella [Saunders] and Bemisia tabaci [Gennadius]) of cotton in the western United States, is unaffected in Bt cotton. |
