Resistance to Bt Maize by Western Corn Rootworm: Effects of Pest Biology, the Pest–Crop Interaction and the Agricultural Landscape on Resistance

Abstract

The western corn rootworm, Diabrotica virgifera virgifera LeConte, is among the most serious pests of maize in the United States. Since 2003, transgenic maize that produces insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) has been used to manage western corn rootworm by killing rootworm larvae, which feed on maize roots. In 2009, the first cases of field-evolved resistance to Bt maize were documented. These cases occurred in Iowa and involved maize that produced Bt toxin Cry3Bb1. Since then, resistance has expanded to include other geographies and additional Bt toxins, with some rootworm populations displaying resistance to all commercially available Bt traits. Factors that contributed to field-evolved resistance likely included non-recessive inheritance of resistance, minimal fitness costs of resistance and limited adult dispersal. Additionally, because maize is the primary agricultural crop on which rootworm larvae can survive, continuous maize cultivation, in particular continuous cultivation of Bt maize, appears to be another key factor facilitating resistance evolution. More diversified management of rootworm larvae, including rotating fields out of maize production and using soil-applied insecticide with non-Bt maize, in addition to planting refuges of non-Bt maize, should help to delay the evolution of resistance to current and future transgenic traits.

Evidence of western corn rootworm (Diabrotica virgifera virgiferaLeConte) field‐evolved resistance to Cry3Bb1 + Cry34/35Ab1 maize in Nebraska

“…Widespread Cry3Bb1 resistance also has been reported in numerous Iowa counties 81,82 . The neighborhood clusters of Cry3Bb1 resistance evident in Nebraska reinforce the role of localized selection pressure and WCR population dynamics as key contributors to resistance evolution within the landscape 45,79–82 …”

“…81,82 The neighborhood clusters of Cry3Bb1 resistance evident in Nebraska reinforce the role of localized selection pressure and WCR population dynamics as key contributors to resistance evolution within the landscape. 45,[79][80][81][82] Larval development metrics such as head capsule width and fresh weight complement survival as potential indicators of the level of WCR resistance present within a population. The Sa1 and LABC populations assayed with Cry3Bb1 (2018, 2019) and Cry3Bb1 + Cry34/35Ab1 (2018) in this study exhibited mean extended development (as measured by head capsule width) typically observed in Bt-susceptible populations, 65,66,71,83 whereas WCR populations exhibiting incomplete resistance to Cry3Bb1 or Cry3Bb1 + Cry34/35Ab1 had variable mean larval development (i.e.…”

RNAi for Western Corn Rootworm Management: Lessons Learned, Challenges, and Future Directions

“…Native to Central America and first identified as a pest of cultivated maize in Colorado in 1909 [3,4], populations are now found throughout the midwestern U.S. and Europe [5,6]. Once achieving pest status, various control tactics have been used to reduce damage caused by WCR larval feeding including crop rotation, soil-applied insecticides, and maize hybrids expressing insecticidal proteins from the soil bacterium Bacillus thuringiensis Berliner (Bt) [2,7,8]. However, managing WCR has been historically challenging due to its remarkable ability to evolve resistance to all available management tactics throughout various local areas in the U.S. Corn Belt [2,7,[9][10][11][12][13][14].…”

“…More recently, resistance to Cry34Ab1/Cry35Ab1 was identified [27,29,30], highlighting the urgency for alternative approaches for WCR management. Recent review articles highlight the history, use of, and evolution of resistance to synthetic insecticides [7] and Bt traits [8].…”

Sequences Encoding a Novel Toursvirus Identified from Southern and Northern Corn Rootworms (Coleoptera: Chrysomelidae)

“…More recently resistance to transgenic maize hybrids that express Bacillus thuringiensis (Bt) pesticidal proteins has been documented in WCR [6][7][8] and NCR [9]. Consequently, a more integrated approach to corn rootworm management has been proposed [10].…”