Does refuge spillover affect arthropod food webs associated with Bt maize

Background The high dose/refuge combination is the main tactic recommended for mitigating resistance selection of target herbivore species in crops expressing insecticidal proteins of the bacterium Bacillus thuringiensis (i.e., Bt proteins). The tactic consists of the simultaneous use of Bt crops expressing high levels of the Bt protein associated with neighboring areas of refuge of the same non-Bt crop species. Nonetheless, the approach faces controversy regarding its effectiveness and scale of adoption at least in some regions. One of the concerns focuses on its potential impact on the arthropod community, including its short-term and spatially dependent impact considering the likely biota spillover effect between Bt- and non-Bt neighboring areas. Thus, the eventual spillover of Bt-maize targeted and non-targeted arthropods was surveyed along transects extending from the refuge border to the center of the Bt maize area. Results The arthropods were collected throughout the maize vegetative and reproductive stages and a total of 85 arthropod species were collected, but their richness and abundance did not vary with distance from the refuge. In contrast, the cultivation season played a significant role in distinguishing the arthropod communities. Refuge distance from the sampling point within Bt-fields did not significantly affect the food web metrics, unlike season, which affected the number of nodes integrating each food web. Winter maize cultivation exhibited higher arthropod diversity and combined values of species numeric abundance and biomass at each trophic level. Conclusions No arthropod spillover was evident between the refuge edge and Bt-maize adding further controversy to the tactic currently subjected to lower usage in the region with disputed cost-benefit relationship, as not even the target and its inter-dependent species were affected. This article is protected by copyright. All rights reserved.