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Characterizing the Susceptibility and Biological Fitness of Nebraska Western Corn Rootworm Populations to Pyramided Plant-Incorporated Protectants
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.
Reinders, Jordan D, "Characterizing the Susceptibility and Biological Fitness of Nebraska Western Corn Rootworm Populations to Pyramided Plant-Incorporated Protectants" (2021). ETD collection for University of Nebraska - Lincoln. AAI28489811.