Dr. Lance J. Meinke
Date of this Version
Reinders, J. D. 2021. Characterizing the susceptibility and biological fitness of Nebraska western corn rootworm populations to pyramided plant-incorporated protectants. Dissertation. University of Nebraska-Lincoln. 1-192.
The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is a pest of field corn, Zea mays L., across the United States (U.S.) Corn Belt. Transgenic corn expressing two or more insecticidal proteins (‘pyramid’) derived from Bacillus thuringiensis Berliner (Bt) is a common management strategy employed in areas of continuous corn production. The newest rootworm-Bt pyramid registered in the U.S. is SmartStax® PRO, which contains two rootworm-Bt proteins (Cry3Bb1, Cry34/35Ab1) and DvSnf7 dsRNA. With the pending commercialization of SmartStax® PRO, understanding the current susceptibility of Nebraska WCR populations to the Cry3Bb1 + Cry34/35Ab1 pyramid (SmartStax®) and characterizing the biological fitness of WCR surviving dietary exposure to SmartStax® PRO is needed to develop effective resistance management strategies.
The first objective was to characterize the susceptibility of northeast Nebraska WCR populations to SmartStax® using the Gassmann plant-based bioassay technique. Results confirmed the first cases of resistance to a rootworm-Bt pyramid in Nebraska and a neighborhood resistance pattern to Cry3Bb1 was observed in the study area.
The second objective was to compare life history traits of WCR surviving dietary exposure to SmartStax® PRO or non-Bt corn. Data were collected from individual WCR male/female pairs selected from adults collected in replicated field plots of SmartStax® PRO or non-Bt corn. Results indicated that adult or lifetime exposure to SmartStax® PRO significantly reduced WCR longevity, size, and lifetime egg production, contributing to a decrease in biological fitness.
The third objective was to characterize the effect of SmartStax® PRO dietary exposure on WCR F1 population dynamics. Individual-based simulation models were used to estimate the intrinsic growth rate (r) based on net reproductive rate (R0) calculated from experimental data. The results confirmed a significant decrease in population growth in the F1 generation caused by the sublethal effects of SmartStax® PRO exposure observed in the F0 generation. Collectively, the results suggest that SmartStax® PRO may contribute to population suppression under field conditions, although additional modeling is needed to test this hypothesis.
Advisor: Lance J. Meinke