Putative effects of Cry1Ab to larvae of Adalia bipunctata - reply to Hilbeck et al. (2012)

In 2009, Schmidt et al. [1] reported that larvae of A. bipunctata suffered increased mortality during the first larval stage when ingesting the Cry1Ab protein that is expressed in some of today’s Bt maize varieties including MON810. This study has been criticized for its design, execution, and data interpretation by several scientists [2,3] and by the Central Commission on Biological Safety that advises the Federal Government of Germany [4,5]. Two subsequent studies in which A. bipunctata larvae were directly fed with Cry1Ab conducted by our group [6] and by Porcar et al. [7] could not confirm this toxic effect. Furthermore we did not detect adverse effects of Bt maize expressing Cry1Ab on larvae of A. bipunctata in a higher tier, tri-trophic study using Bt maize-fed spider mites as prey [6].In their paper “A controversy re-visited: Is the coccinellid Adalia bipunctata adversely affected by Bt toxins?”, Hilbeck et al. [8] confirm the findings from their earlier study [1] but do not convincingly address the critical issues regarding study design and execution. While Hilbeck et al. [8] criticize the design and execution of our direct feeding experiment [6], they do not acknowledge our tri-trophic feeding study and the study by Porcar et al. [7].In this letter we respond to the main points of criticism by Hilbeck et al. [8] on our direct feeding study and discuss the available data in a wider risk assessment context. The fact that we do not address certain statements and claims made by Hilbeck et al. [8] does not imply that we agree with them.In total, three studies prior to Hilbeck et al. [8] have assessed the effect of Cry1Ab on A. bipunctata larvae using different test protocols.In the study by Schmidt et al. [1], Cry1Ab was dissolved in a buffer solution and deposited on eggs of Ephestia kuehniella, which were continuously provided to A. bipunctata larvae. The Cry1Ab was applied at three different concentrations (5, 25, and 50？μg/ml). First instar larvae in the Bt