Effects of gene flow between Bt and non‐Bt plants in a seed mixture of Cry1A.105 + Cry2Ab corn on performance of corn earworm in Arizona. Issue 4 (5th January 2021)

• Record Type: Journal Article
• Authors: Carrière, Yves; Degain, Ben A; Tabashnik, Bruce E
• Is Part Of: Pest management science. Volume 77:Issue 4(2021)
• Page Start: 2106
• Page End: 2113
• Publication Date: 2021-01-05
• Subjects: Bt corn -- cross‐pollination -- Helicoverpa zea -- refuge in a bag -- seed blend -- refuge mandates; Pests -- Control -- Periodicals; Pesticides -- Periodicals; 632.9
• DOI: 10.1002/ps.6239
• Languages: English
• ISSNs: 1526-498X

Abstract

Abstract: BACKGROUND: Using natural populations of Helicoverpa zea from Arizona, we tested the hypotheses that gene flow between Bacillus thuringiensis (Bt) plants and non‐Bt plants in a seed mixture of 10% non‐Bt corn and 90% Bt corn producing Cry1A.105 and Cry2Ab reduces larval performance on ears from non‐Bt plants, or increases performance on ears from Bt plants. RESULTS: Gene flow was not detected in blocks of non‐Bt or Bt corn but was extensive in seed mixtures. Analyses of larval weight and abundance over a period of 3 to 4 weeks did not indicate consistent effects of gene flow on development rate and survival. However for non‐Bt plants, the ear area damaged and percentage of ears with exit holes were significantly lower in the seed mixtures than blocks. By contrast, the percentage of ears with exit holes and ear damage did not differ significantly between the seed mixtures and blocks for Bt plants. Nearly 100% of the ears were damaged and the damaged area was substantial, showing that H. zea is a major ear‐feeding pest in Arizona. Relative to non‐Bt corn, the pyramided Bt corn did not significantly reduce the percentage of damaged ears and only reduced the ear area damaged by 21 to 39%, indicating that H. zea may have evolved resistance to Cry1A.105, Cry2Ab, or both. CONCLUSIONS: Our results indicate that gene flow between Bt and non‐Bt plants in seed mixtures reduced effective refuge size, and that block refuges may be needed to manage the evolution of H. zea resistance to Bt corn in Arizona. © 2020 Society of Chemical Industry Abstract : Seed mixtures of Bacillus thuringiensis (Bt) and non‐Bt corn reduced effective refuge size for Helicoverpa zea . Block refuges may be needed to manage evolution resistance to Bt for this pest in Arizona. © 2020 Society of Chemical Industry