The Use of Insecticides to Manage the Western Corn Rootworm, Diabrotica virgifera virgifera, LeConte: History, Field-Evolved Resistance, and Associated Mechanisms

SIMPLE SUMMARY: The structure of agricultural enterprises in the western United States Corn Belt (large irrigated monocultures, continuous planting of maize, strong aerial pesticide application and livestock industries) has led to a tradition of extensive insecticide use over time to manage the western corn rootworm, Diabrotica virgifera virgifera LeConte (Dvv) a key insect pest of maize. Dvv damages maize roots, which can cause maize plant instability, reduced plant growth, and significant yield loss. Long-term insecticide use has contributed to Dvv becoming resistant to cyclodiene, organophosphate, carbamate, and pyrethroid insecticides since the 1950s. This paper reviews the historical and current use of insecticides in Dvv management programs and Dvv adaptation to insecticide use. Currently, insecticides have a reduced role in Dvv management programs but are still used as complementary tactics with other management approaches. Past history suggests that the probability of selecting for resistance to any future Dvv control technology will be high if it is not used within an integrated pest management framework with other tactics. ABSTRACT: The western corn rootworm, Diabrotica virgifera virgifera LeConte (Dvv) is a significant insect pest of maize in the United States (U.S.). This paper reviews the history of insecticide use in Dvv management programs, Dvv adaptation to insecticides, i.e., field-evolved resistance and associated mechanisms of resistance, plus the current role of insecticides in the transgenic era. In the western U.S. Corn Belt where continuous maize is commonly grown in large irrigated monocultures, broadcast-applied soil or foliar insecticides have been extensively used over time to manage annual densities of Dvv and other secondary insect pests. This has contributed to the sequential occurrence of Dvv resistance evolution to cyclodiene, organophosphate, carbamate, and pyrethroid insecticides since the 1950s. Mechanisms of resistance are complex, but both oxidative and hydrolytic metabolism contribute to organophosphate, carbamate, and pyrethroid resistance facilitating cross-resistance between insecticide classes. History shows that Dvv insecticide resistance can evolve quickly and may persist in field populations even in the absence of selection. This suggests minimal fitness costs associated with Dvv resistance. In the transgenic era, insecticides function primarily as complementary tools with other Dvv management tactics to manage annual Dvv densities/crop injury and resistance over time.