Abstract

Simple SummaryThe 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.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.

Highlights

  • The western corn rootworm, Diabrotica virgifera virgifera LeConte (Dvv) is a galerucerine Chrysomelid beetle (Figure 1A) that is one of the most significant insect pests of maize (Zea mays L.) in the United States (U.S.)

  • The history of insecticide use to manage Dvv clearly reveals a common thread among all documented cases of Dvv resistance evolution, namely population management

  • This combined with repeated use of the same insecticides over Dvv generations led to field-evolved resistance

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Summary

Introduction

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Dvv) is a galerucerine Chrysomelid beetle (Figure 1A) that is one of the most significant insect pests of maize (Zea mays L.) in the United States (U.S.). A similar scenario occurred with the organophosphate isophenphos This soil insecticide was initially marketed as Amaze® in 1981 but by 1983, Dvv control failures were reported from various locations in the U.S Corn Belt in fields where the product had been used the previous year [59]. There is often an inconsistent relationship between soil insecticide efficacy as measured by level of root injury and subsequent adult emergence This built-in refuge is probably a major reason why field-evolved Dvv resistance attributed to direct selection of Dvv larvae has only been documented with broadcast-applied cyclodiene insecticides but not insecticides applied in-furrow or banded over the row [83,86,87]. In 1996, the Food Quality Protection Act altered the regulation of pesticides in the U.S and the USEPA canceled uses of a number of organophosphate and carbamate insecticides, which has greatly reduced the insecticide options available for larval Dvv control

Seed Treatments
Foliar Insecticides
Carbamates and Organophosphates
Pyrethroids
Findings
Conclusions
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