|GUO, Y.Y. - China Agricultural University
|TIAN, J.C. - China Agricultural University
|SHI, W.P. - Zhejiang Academy Of Agricultural Sciences
|DONG, X.H. - China Agricultural University
|ROMEIS, J. - Agroscope
|Hellmich Ii, Richard
|SHELTON, A.M. - Cornell University
Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2015
Publication Date: 11/6/2015
Citation: Guo, Y., Tian, J., Shi, W., Dong, X., Romeis, J., Naranjo, S.E., Hellmich Ii, R.L., Shelton, A. 2015. The interaction of two-spotted spider mites, Tetranychus urticae Koch, with Cry protein production and predation by Amblyseius andersoni (Chant) in Cry1Ac/Cry2Ab cotton and Cry1F maize. Transgenic Research. 25(1):33-44.
Interpretive Summary: Transgenic cotton and maize producing the Cry proteins of Bacillus thuringiensis (Bt) have been adopted worldwide as an effective tactic for control of serious lepidopteran pests. The environmental risk assessment of such crops has focused on non-target organisms such as beneficial arthropod predators that provide important ecosystem services. This study examined Amblyseius andersoni, a cosmopolitan predator of the two-spotted spider mite, Tetranychus urticae, which is a significant pest of cotton and maize. Tri-trophic studies (predators feeding on prey that had consumed Bt crop tissue) were conducted to assess the potential effects of three common Cry proteins found in commercial cottons and maize. We found no changes in life history parameters (survival rate, development time, fecundity and egg hatching rate) of the predator and confirmed that these Bt crops have no effects on the biology of pest mite. We further confirmed that the pest mite contained biologically active Cry proteins. Levels of Cry proteins declined greatly as they moved from plants to herbivores to predators. Free-choice experiments revealed that the predator had no preference for Bt cotton or Bt maize-reared pest mites compared with those reared on non-Bt cotton or maize. However, we did observe that levels of Cry proteins in Bt plants were affected by the time of exposure to pest mites and in one case (Cry2Ab) by mite density. However, none of these changes would have biological relevance to control of lepidoperan pests with Bt crops in the field. Our findings show that we would not expect this predator to be affected in the field and that it would continue to supply valuable biological control services in Bt crops. These results should be useful to governmental regulators, scientists interested in ecological risk assessment and others concerned about the risks of Bt transgenic crops.
Technical Abstract: Crops producing insecticidal crystal (Cry) proteins from the bacterium, Bacillus thuringiensis (Bt), are an important tool for managing lepidopteran pests on cotton and maize. However, the effects of these Bt crops on non-target organisms, especially natural enemies that provide biological control services, are required to be addressed in an environmental risk assessment. Amblyseius andersoni (Acari: Phytoseiidae) is a cosmopolitan predator of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), a significant pest of cotton and maize. Tri-trophic studies were conducted to assess the potential effects of Cry1Ac/Cry2Ab cotton and Cry1F maize on life history parameters (survival rate, development time, fecundity and egg hatching rate) of A. andersoni. We confirmed that these Bt crops have no effects on the biology of T. urticae and, in turn, that there were no differences in any of the life history parameters of A. andersoni when it fed on T. urticae feeding on Cry1Ac/Cry2Ab or non-Bt cotton and Cry1F or non-Bt maize. Use of a susceptible insect assay demonstrated that T. urticae contained biologically active Cry proteins. Cry proteins concentrations declined greatly as they moved from plants to herbivores to predators and protein concentration did not appear to be related to mite density. Free-choice experiments revealed that A. andersoni had no preference for Cry1Ac/Cry2Ab cotton or Cry1F maize-reared T. urticae compared with those reared on non-Bt cotton or maize. Collectively these results provide strong evidence that these crops can complement other integrated pest management tactics including biological control.