Lance J Meinke
Date of this Version
Souza, D. 2019. Characterization of pyrethroid resistance in the western corn rootworm Diabrotica virgifera virgifera LeConte. ETD collection for University of Nebraska - Lincoln.
The western corn rootworm (WCR), Diabrotica virgifera virgifera Le Conte (Coleoptera: Chrysomelidae), is a major pest of maize (Zea mays L.) in the United States and has continuously challenged our ability to develop sustainable pest management solutions. Resistance to chemical insecticides, crop rotation, and most recently transgenic plants that express toxins derived from Bacillus thuringiensis Berliner (Bt) have been well documented among WCR populations. Furthermore, US regulatory insecticide prohibitions and the lack of new active ingredients have reduced the options for WCR control. Pyrethroid insecticides are one of the few remaining chemical options. Therefore, the recent confirmation of WCR field-evolved resistance to pyrethroids in the US western Corn Belt is a major concern. The present research aimed to characterize WCR pyrethroid resistance.
The initial objective was to evaluate the field performance of formulated pyrethroids on pyrethroid-resistant WCR populations. An aerial application simulation method was developed to evaluate the performance of foliar adulticides whereas soil insecticides targeting WCR larvae were tested in field plots with representative WCR populations. Laboratory bioassays estimated the susceptibility of tested WCR populations against the active ingredients of formulated insecticides. Results indicated that relatively low levels of WCR pyrethroid resistance are enough to significantly impact the performance of pyrethroid products commonly used for either adult or larval control.
A second objective was to artificially select a pyrethroid-resistant WCR population to be used along with field populations for pyrethroid resistance characterization. A population was selected in the laboratory with a diagnostic bifenthrin concentration for several generations reaching levels of pyrethroid resistance observed in field-collected WCR populations. A pilot heritability investigation suggested that a major portion of WCR bifenthrin resistance phenotypic variance may be due to genetic variation, and that a substantial increase in resistance could be expected afterexposure.
Finally, the third objective was to identify WCR pyrethroid resistance mechanisms. Biochemical assays and High-Throughput RNA Sequencing results revealed that insecticide-related metabolism in pyrethroid-resistant WCR populations was significantly enhanced compared to pyrethroid-susceptible populations. The relevance of results is discussed within the context of WCR pyrethroid resistance monitoring and management.
Advisor: Lance J. Meinke