Degree Type


Date of Award


Degree Name

Master of Science



First Advisor

Aaron J. Gassmann


Corn rootworms (Diabrotica spp.) are one of the most destructive pests of corn in the United States. Bt corn or corn that has been genetically modified to produce toxins from Bacillus thuringiensis has been rapidly adopted by growers to manage the feeding of these pests. We examined how the western ( Diabrotica virgifera virgifera) and northern (Diabrotica barberi) corn rootworm react to selection on Bt corn hybrids. The treatments were YieldGard VT Triple (Cry3Bb1), SmartStax (Cry3Bb1 and Cry34/35Ab1), SmartStax with a blended refuge of non-Bt corn and pure non-Bt corn. We also examined how the progeny of western corn rootworm react to selection on these hybrids using an F1 screen. The data show that the pyramided hybrid was the most effective at controlling rootworm and that exposure to Bt corn typically delayed the mean emergence time of these beetles compared to beetles reared on non-Bt corn. The data also show that after beetles were selected on Bt, the progeny exhibited no difference in survival when screened on Bt plants. The progeny also did not experience any delays in development on Bt corn after selection although genetic variation for survival was higher for the single toxin hybrid. Finally, there were significant correlations for survival on both the Bt hybrids in the screen when the insects were selected on YieldGard VT Triple and SmartStax with a blended refuge. This information is important when considering the insect resistance management of these species on Bt corn.


Copyright Owner

Ryan Scott Keweshan



File Format


File Size

85 pages

Included in

Entomology Commons