title: A challenge for the seed mixture refuge strategy in Bt maize: impact of cross-pollination on an ear-feeding pest, corn earworm.
abstract: To counter the threat of insect resistance, Bacillus thuringiensis (Bt) maize growers in the U.S. are required to plant structured non-Bt maize refuges. Concerns with refuge compliance led to the introduction of seed mixtures, also called RIB (refuge-in-the-bag), as an alternative approach for implementing refuge for Bt maize products in the U.S. Maize Belt. A major concern in RIB is cross-pollination of maize hybrids that can cause Bt proteins to be present in refuge maize kernels and negatively affect refuge insects. Here we show that a mixed planting of 5% nonBt and 95% Bt maize containing the SmartStax traits expressing Cry1A.105, Cry2Ab2 and Cry1F did not provide an effective refuge for an important above-ground ear-feeding pest, the corn earworm, Helicoverpa zea (Boddie). Cross-pollination in RIB caused a majority (>90%) of refuge kernels to express ≥ one Bt protein. The contamination of Bt proteins in the refuge ears reduced neonate-to-adult survivorship of H. zea to only 4.6%, a reduction of 88.1% relative to larvae feeding on ears of pure non-Bt maize plantings. In addition, the limited survivors on refuge ears had lower pupal mass and took longer to develop to adults.
authors.affiliation: Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, 70803, United States of America.
authors.forename: Fei
authors.initials: F
authors.lastname: Yang
authors.affiliation: Macon Ridge Research Station, Louisiana State University Agricultural Center, Winnsboro, Louisiana, 71295, United States of America.
authors.forename: David L
authors.initials: DL
authors.lastname: Kerns
authors.affiliation: Monsanto Company, St. Louis, Missouri, 63167, United States of America.
authors.forename: Graham P
authors.initials: GP
authors.lastname: Head
authors.affiliation: Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, 70803, United States of America.
authors.forename: B Rogers
authors.initials: BR
authors.lastname: Leonard
authors.affiliation: Dean Lee Research Station, Louisiana State University Agricultural Center, Alexandria, Louisiana, 71302, United States of America.
authors.forename: Ronnie
authors.initials: R
authors.lastname: Levy
authors.affiliation: Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, 70803, United States of America.
authors.forename: Ying
authors.initials: Y
authors.lastname: Niu
authors.affiliation: Department of Entomology, Louisiana State University Agricultural Center, Baton Rouge, Louisiana, 70803, United States of America.
authors.forename: Fangneng
authors.initials: F
authors.lastname: Huang
mesh_terms: D000821:Animal Feed; D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics*; D003657:Decision Making; D007915:Lepidoptera / Q000254:growth & development; D010572:Pest Control, Biological / Q000379:methods*; D030821:Plants, Genetically Modified; D054817:Pollination; D012639:Seeds / Q000235:genetics*; D016019:Survival Analysis; D003313:Zea mays / Q000235:genetics* / Q000502:physiology*