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

Abstract

In their recent study, Hilbeck et al. (2012) report that Cry1Ab causes lethal effects on larvae of the ladybird beetle Adalia bipunctata when fed directly to the predator. Such toxic effects were not previously observed in a direct feeding study conducted by us (Álvarez-Alfageme et al. 2011). Because Hilbeck et al. (2012) claim that our study design did not allow us to detect any adverse effects we provide arguments for the value and relevance of our study in this commentary. Furthermore we discuss two additional published studies that have not revealed any direct effects of Cry1Ab on larvae of A. bipunctata and are not mentioned by Hilbeck et al. (2012). One of the studies was conducted in our laboratory under more realistic exposure conditions (Álvarez-Alfageme et al. 2011). Feeding A. bipunctata larvae with spider mites reared on Bt maize did not reveal any adverse effects on lethal and sublethal parameters of the predator. This was despite the fact that the larvae had ingested high amounts of biologically-active Cry1Ab protein. Thus, we do not see verified evidence that A. bipunctata larvae are sensitive to Cry1Ab at realistic worst-case exposure concentrations. This, together with the fact that A. bipunctata will be little exposed to Cry1Ab under field conditions, allows us to conclude that the risk of Bt maize to this predator is negligible. Support for this comes from the results of many Bt maize field studies that have not revealed evidence for direct Cry1Ab-effects on non-Lepidoptera species. © 2012 Romeis et al.