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Quantifying rates of random mating in western corn rootworm emerging from Cry3Bb1 ‐expressing and refuge maize in field cages
Author(s) -
Taylor Sally V.,
Smith Steven J.,
Krupke Christian H.
Publication year - 2016
Publication title -
entomologia experimentalis et applicata
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.765
H-Index - 83
eISSN - 1570-7458
pISSN - 0013-8703
DOI - 10.1111/eea.12513
Subject(s) - western corn rootworm , biology , pest analysis , mating , agronomy , genetically modified maize , larva , dry weight , ecology , genetically modified crops , botany , biochemistry , transgene , gene
Abstract The western corn rootworm ( WCR ), D iabrotica virgifera virgifera LeConte ( C oleoptera: C hrysomelidae), is the most significant pest of field maize, Z ea mays L. ( P oaceae), in the USA . Maize plants expressing Bt toxins targeting the corn rootworm complex have been widely adopted and are the primary insecticidal control measure for this pest in North America. Insect resistance management tactics using various refuge structures have been adopted to ensure Bt products will retain durability. An assumption of the refuge strategy is that males and females emerging from Bt and refuge plantings mate randomly; this has not been tested in the field. We conducted cage studies using field populations of WCR in Indiana, USA , to generate empirical field data on mating rates between beetles emerging from Cry3Bb1 ‐expressing Bt and refuge maize plants. Two refuge configurations were tested; all refuge plants were labeled using the stable isotope 15 N. This mark persists in adult beetles after eclosion, allowing for collection and analysis of isotopic ratios of all beetles. Additional data collected included adult emergence rates, timing and sex ratios for each of the treatments, and head capsule size and dry weights of beetles collected. Treatment had a significant effect on dry weight; mean dry weight decreased in Bt‐only treatments. Fisher's exact test of proportions of mating pairs of refuge and Bt insects indicated that mating was not random in 20% strip refuges and 5% seed blend treatments. We found high percentages of beetles that fed on Bt‐expressing plants as larvae, suggesting that mating between resistant beetles may not be rare even if random mating did occur.