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Title: Video-tracking and on-plant tests show Cry1Ab resistance influences behavior and survival of neonate Ostrinia nubilalis following exposure to Bt maize

Author
item PRASIFKA, JARRAD - University Of Illinois
item Hellmich Ii, Richard
item CRESPO, ANDRE - Syngenta Biotech, Inc
item SIEGFRIED, BLAIR - University Of Nebraska
item ONSTAD, DAVID - University Of Illinois

Submitted to: Journal of Insect Behavior
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2009
Publication Date: 1/1/2010
Citation: Prasifka, J.R., Hellmich Ii, R.L., Crespo, A.L., Siegfried, B.D., Onstad, D.W. 2010. Video-tracking and on-plant tests show Cry1Ab resistance influences behavior and survival of neonate Ostrinia nubilalis following exposure to Bt maize. Journal of Insect Behavior. 23(1):1-11.

Interpretive Summary: Interplant movement of insect larvae can influence how fast resistance to transgenic Bacillus thuringiensis (Bt) crops develops in the field. However, movement behavior of European corn borer larvae is largely unknown, especially whether larvae with genes that contribute to resistance behave differently than larvae without such genes. Bt resistant, susceptible, and hybrid (Bt resistant x susceptible) larvae (neonates) were tested in two experiments. In the first experiment an automated video-tracking system measured various aspects of movement for the three types of larvae when they were put in arenas with artificial diet that contained either 50% Bt tissue or 50% non-Bt tissue. In the second experiment larval dispersal and survival were measured 48–72 hours after hatching on a Bt maize plant surrounded by two non-Bt maize plants. Video tracking indicated Bt resistant larvae showed reduced movement and increased localized searching relative to susceptible or hybrid larvae on Bt diet. Conversely, when placed onto Bt maize plants, resistant larvae were more likely than susceptible larvae to disperse onto adjacent non-Bt plants. The difference in on-plant dispersal seems to reflect greater survival after toxin exposure for resistant larvae rather than increased activity. Because models of European corn borer resistance evolution incorporate various movement and survival parameters, improved data for on-plant behavior and survival of resistant, susceptible, and hybrid larvae should help preserve the efficacy of Bt maize. This information is useful for all stakeholders interested in preserving the effectiveness of Bt crops as pest control tools for agriculture.

Technical Abstract: To examine how resistance to Bacillus thuringiensis (Bt) toxins influences movement and survival of European corn borer (Ostrinia nubilalis) neonates, the responses of Cry1Ab-resistant, -susceptible, and hybrid (F1) larvae were examined using two different techniques. First, using an automated video-tracking system, aspects of O. nubilalis movement were quantified in the presence of artificial diet incorporating 50% non-Bt or insect-resistant Cry1Ab maize tissue. Second, O. nubilalis dispersal and survival were measured 48–72 hours after hatching on a Cry1Ab maize plant surrounded by two non-Bt maize plants. Video tracking indicated the presence of Cry1Ab tissue increased the total distance moved (m), time moving (%), and time away from the diet (%) for O. nubilalis while decreasing meander (degrees/cm). However, resistant larvae showed reduced movement and increased meander (localized searching) relative to susceptible or hybrid larvae on diet incorporating Cry1Ab tissue. Conversely, when placed onto Cry1Ab maize plants, resistant larvae were more likely than susceptible O. nubilalis to disperse onto adjacent non-Bt plants. The difference in on-plant dispersal seems to reflect greater survival after toxin exposure for resistant larvae rather than increased activity. These results suggest that simplified "Petri dish" tests may not be predictive of larval movement among non-Bt and insect-resistant Bt maize plants. Because models of O. nubilalis resistance evolution incorporate various movement and survival parameters, improved data for on-plant behavior and survival of Bt- resistant, -susceptible, and hybrid larvae should help preserve the efficacy of transgenic insect-resistant maize.