Entomology, Department of


First Advisor

Ana M. Vélez Arango

Second Advisor

Lance J. Meinke

Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Entomology, Under the Supervision of Professor Ana M. Vélez Arango and Lance J. Meinke, Lincoln, Nebraska: December, 2019

Copyright (c) 2019 Matthew J. Welter


The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is the most damaging corn pest in the U.S. Corn Belt, costing producers over $1 billion annually in control and damage costs. Currently, corn producers rely on three control strategies for WCR management: crop rotation, chemical insecticides, and transgenic corn expressing Bacillus thuringiensis Berliner (Bt) proteins. Populations of WCR have evolved resistance to all of these tactics, limiting effective control strategies for producers. RNA interference (RNAi), is the newest mode of action developed for WCR management. In July 2017, the first RNAi plant-incorporated protectant (PIP) corn product was approved for production in the United States. This product, marketed under the trade name SmartStax PRO®, will express two Bt proteins and DvSnf7 double-stranded RNA for WCR control. Similar to current PIPs, resistance monitoring protocols must be established before adoption of this technology to delay resistance evolution.

This study characterized the variability of adult susceptibility due to age and sex. Male beetles were most tolerant to dsRNA at 2-days post-emergence, but responded uniformly to dsRNA at 10-, 20-, and 30-days post-emergence and were significantly more susceptible than their female counterparts at 10- and 20-days post-emergence. Female adults responded uniformly for 2-, 10-, and 20-days post-emergence, but were significantly more susceptible at 30-days post-emergence. Baseline susceptibilities for U.S. Corn Belt populations of WCR were established and the potential for use of adult WCR for DvSnf7 dsRNA susceptibility monitoring in field populations was evaluated. Overall, most field populations were uniform in their larval susceptibility to DvSnf7 dsRNA. Adult male susceptibility was more variable compared to larvae and correlation ratios between adult males and larvae were not always consistent. Therefore, it may not be possible to use adult WCR to monitor changes in DvSnf7 dsRNA susceptibility, especially if small shifts in susceptibility impact product performance.

Advisors: Ana M. Vélez Arango and Lance J. Meinke

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Entomology Commons