An assessment of refuge-in–a-bag and other refuge structures used in managing resistance to transgenic corn in western corn rootworm (Diabrotica virgifera virgifera LeConte)

The western corn rootworm, Diabrotica virgifera virgifera LeConte is an important pest of corn in North America and responsible for the loss of $1 billion in revenue each year. In an effort to control this destructive beetle, increasing amounts of transgenic corn containing Bacillus thuringiensis (or Bt) toxin are being planted throughout the Midwest. To manage the development of resistance to the toxin, the Environmental Protection Agency mandated that 20% of the acreage containing transgenic corn must be planted with corn that does not contain Bt toxin as a refuge. This refuge can be planted either in a block adjacent to a plot of transgenic corn or as strips within the field. With another potential refuge structure, known as refuge-in-a-bag, commercial refuge seed is mixed with transgenic hybrids. Implementation of the refuge-in-a-bag refuge structure would alleviate concerns regarding compliance to the EPA guidelines. In this study, we measured both economic (i.e., root damage and yield) and biological (i.e., beetle emergence timing, sex ratio, and abundance) parameters to determine the relative benefits and disadvantages of these three refuge structures. The results of this work will be discussed from the perspective of balancing present and future resistance management with the economic realities of production agriculture.