Simple SummaryThe planting of genetically modified crops that express insecticidal proteins is central to modern pest management, particularly for maize and cotton in the United States. An understanding of how the presence of transgenic proteins can affect the movement and feeding behavior of insect pests will allow us to better design resistance management strategies to prolong the use of this technology. In this study, the western bean cutworm, a regionally important pest of maize, was studied in artificial arena and on-plant experiments. Two more artificial experiments did not indicate significant changes to young caterpillar behavior when exposed to maize tissues expressing transgenic proteins; however, the more field-realistic and longer exposure period studies did indicate that young caterpillars would abandon plants that expressed transgenic proteins more often that those that did not. This finding has particular importance for the use of integrated versus structured refuges.AbstractExposure of lepidopteran pests toBacillus thuringiensis(Bt) proteins has been shown to affect the behavior of larvae, including increased movement and avoidance ofBt-expressing plants or diet. Therefore, we hypothesized that the behavior of western bean cutworm,Striacosta albicosta(Smith) (Lepidoptera: Noctuidae), an important pest of maize, could be affected when exposed toBtplants. To test this hypothesis, we conducted a series of artificial arena and on-plant experiments to determineS. albicostaneonate behavior when exposed toBtand non-Btplant tissue. Video tracking experiments presented neonate larvae with the choice ofBtor non-Btpollen in a Petri dish for 15 min while being video recorded for analysis with EthoVision software. This study showed an increase in mean velocity and total time spent moving for larvae in the presence of Cry1F vs. non-Btwhen compared with Vip3A vs. non-Btor Cry1F vs. Vip3A. However, there was no difference in total distance moved or time spent in the food zone for all scenarios. Maize tissue choice experiments allowed neonatal larvae the choice of feeding onBtor non-Bttassel or leaves for 9 h in Petri dish arenas. This experiment showed that larvae preferred tassel tissue over leaves but did not indicate that larvae could distinguish betweenBtand non-Bttissue. In contrast, on-plant experiments (including a whole plant neonate dispersal study under controlled conditions and an in-field silking behavior experiment) indicated that the presence of Cry1F and Vip3ABttoxins increased plant abandonment, suggesting that larvae are able to detect and avoidBttoxins. The discrepancy of these results is likely due to the on-plant studies providing more field-realistic environmental conditions and a longer duration of exposure to Bt toxins for the behavioral experiments. Our results represent the first steps in understanding the complex behavior ofS. albicostawhen exposed toBtplants. A better understanding of the response of larvae when exposed toBttraits can aid in the management of this pest, particularly for the design of resistance management strategies and refuge design.