Degree Type

Dissertation

Date of Award

2013

Degree Name

Doctor of Philosophy

Department

Entomology

First Advisor

Richard Hellmich

Second Advisor

Joel Coats

Abstract

Bacillus thuringiensis (Bt) maize (Zea mays) was developed primarily for North American pests such as European corn borer (Ostrinia nubilalis). However, most Bt maize products are also cultivated outside of North America, where the primary pests are different and often have lower susceptibility to Bt toxins. As these Bt maize products are commercialized in new geographies, insect resistance management (IRM) plans for those geographies need to consider these new pest and toxin combinations, instead of assuming the same refuge strategy applies to all pests in all geographies. Before implementing an IRM plan that includes size, placement and configuration of refuge, it is useful to understand the biology and susceptibility of the important pest(s) in each geography. Fall armyworm (Spodoptera frugiperda) and black cutworm (Agrotis ipsilon) are examples of global pests with unique biology and susceptibility to Cry1F (expressed in event 1507). The initial behavioral response of each species to Cry1F maize was tested by measuring the time nave third instars spent feeding during a three-minute exposure. I also investigated whether these species had a behavioral and/or toxic response to Cry1F maize. Additional investigation of species susceptibility and ability to overcome an aversive response was conducted by exposing third-instars of each species to Cry1F maize and measuring weight gain and survival for 14 days.

Both S. frugiperda and A. ipsilon demonstrated an initial, aversive response to Cry1F maize. The response of S. frugiperda was post-ingestive, and few larvae survived a 14 d exposure. The response of A. ipsilon to Cry1F maize was post-ingestive, and 40% of the larvae survived a 14 d exposure. A. ipsilon also demonstrated an initial aversive response to Cry34Ab1/Cry35Ab1 (expressed in event 59122 maize) leaf tissue. However, all A. ipsilon larvae survived a 14 d exposure to Cry34Ab1/Cry35Ab1 maize. The interaction and significance of susceptibility and avoidance are discussed in the context of global IRM plan development for Bt maize products.

DOI

https://doi.org/10.31274/etd-180810-3241

Copyright Owner

Rachel Renee Binning

Language

en

File Format

application/pdf

File Size

108 pages

Included in

Entomology Commons

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