Effects of multiple Bt proteins and GNA lectin on in vitro-reared honey bee larvae

The honey bee is a key non-target arthropod in environmental risk assessments of genetically modified crops. We analyzed for the first time combined effects of three Bt proteins conferring insect resistances, and a CP4-protein conferring an herbicide resistance as simultaneously expressed in one GM maize. Furthermore, the biosafety of Galanthus nivalis agglutinin (GNA lectin), a candidate protein for pest control was tested. Under worst-case exposure scenario, by using controlled in vitro larvae rearing, the combination of Bt proteins showed no adverse effects on bee larvae. In contrast, the GNA lectin was toxic at a 144 h LD 50 of 16.3 μg/larva. The prepupal weight was found to differ between the larvae collection days and between the colonies used for the experiment, explaining up to five times more data variance than the protein treatments ( N = 709 prepupae). In conclusion, neither single nor a mix of different Bt proteins were found harmful to honey bee larvae.