Environmental risk assessment for the small tortoiseshell Aglais urticae and a stacked Bt-maize with combined resistances against Lepidoptera and Chrysomelidae in central European agrarian landscapes

Abstract

The cultivation of Lepidoptera-resistant Bt-maize may affect nontarget butterflies. We assessed the risk posed by event MON89034 × MON88017 (expressing Cry1A.105 and Cry2Ab2 against corn borers) to nontarget Lepidoptera. Using the small tortoiseshell Aglais urticae, a butterfly species common in central Europe, as a test organism we (i) assessed the toxicity of Bt-maize pollen on butterfly larvae; (ii) measured pollen deposition on leaves of the host plant Urtica dioica; (iii) mapped the occurrence and distribution of host plants and larvae in two arable landscapes in Germany during maize anthesis; and (iv) described the temporal occurrence of a 1-year population of A. urticae. (i) Larvae-fed 200 Bt-maize pollen grains/cm(2) had a reduced feeding activity. Significant differences in developmental time existed at pollen densities of 300 Bt-maize pollen grains/cm(2) and in survival at 400 grains/cm(2). (ii) The highest pollen amount found was 212 grains/cm(2) at the field margin. Mean densities were much lower. (iii) In one region, over 50% of A. urticae nests were located within 5 m of a maize field, while in the other, all nests were found in more than 25 m distance to a maize field. (iv) The percentage of larvae developing during maize anthesis was 19% in the study area. The amount of pollen from maize MON89034 × MON88017 found on host plants is unlikely to adversely affect a significant proportion of larvae of A. urticae. This paper concludes that the risk of event MON89034 × MON88017 to populations of this species is negligible.