Bt maize pollen exposure and impact on the garden spider, Araneus diadematus

Concerns have been raised that Bt maize pollen may have adverse effects on non-target organisms; consequently, there is a general call for Bt maize risk assessment evaluating lethal and sublethal side effects. Spiders play an important economic and ecological role as pest predators in various crops, including maize. Web-building spiders, especially, may be exposed to the Cry1Ab toxin of Bt maize by the ingestion of pollen via 'recycling' of pollen-dusted webs and intentional pollen feeding. In this study, the potential Bt maize pollen exposure of orb-web spiders was quantified in maize fields and adjacent field margins, and laboratory experiments were conducted to evaluate the possible effects of Bt maize pollen consumption on juvenile garden spiders, Araneus diadematus (Clerck) (Araneae: Araneidae). In maize fields and neighbouring field margins, web-building spiders were exposed to high amounts of Bt maize pollen. However, a laboratory bioassay showed no effects of Bt maize pollen on weight increase, survival, moult frequency, reaction time, and various web variables of A. diadematus. A pyrethroid insecticide (Baythroid) application affected weight increase, survival, and reaction time of spiders negatively. In conclusion, the insecticide tested showed adverse effects on the garden spider, whereas the consumption of Bt maize pollen did not. This study is the first one on Bt maize effects on orb-web spiders, and additional research is recommended in order to account for further spider species, relative fitness parameters, prey-mediated effects, and possible long-term chronic consequences of Bt exposure.