A critical component of managing resistance to insecticide in crop pests like the corn earworm (Helicoverpa zea) is the use of refuge crops that lack insecticidal traits, such as expression of Bacillus thuringiensis (Bt) proteins, alongside crops that do express the insecticidal traits. But growers face a question: whether to plant a separate nearby refuge field of non-insecticidal crops or to use a blended mixture of seeds that produce both in the same field. A new review of existing research on this question suggests the answer is highly dependent on the characteristics of individual pest species. (Photo credit: Whitney Cranshaw, Colorado State University, Bugwood.org)