Media type: E-Article Title: Impact of Spodoptera frugiperda neonate pretreatment conditions on Vip3Aa19 insecticidal protein activity and laboratory bioassay variation Contributor: Da Silva, Karen F; Spencer, Terence A; Camargo Gil, Carolina; Siegfried, Blair D; Walters, Frederick S imprint: Wiley, 2016 Published in: Pest Management Science Language: English DOI: 10.1002/ps.4175 ISSN: 1526-4998; 1526-498X Keywords: Insect Science ; Agronomy and Crop Science ; General Medicine Origination: Footnote: Description: <jats:title>Abstract</jats:title><jats:sec><jats:title>BACKGROUND</jats:title><jats:p>Variation in response to insecticidal proteins is common upon repetition of insect bioassays. Understanding this variation is a prerequisite to detecting biologically important differences. We tracked neonate <jats:italic>Spodoptera frugiperda</jats:italic> (J.E. Smith) susceptibility to <jats:styled-content style="fixed-case">Vip3Aa19</jats:styled-content> over 17 generations using standardized bioassay methods. Five larval pretreatment conditions and one bioassay condition were tested to determine whether susceptibility was affected. These included: storage time; prefeeding; storage at reduced temperature; storage at reduced humidity; colony introgression of field‐collected individuals. Extremes of photoperiod during the bioassay itself were also examined.</jats:p></jats:sec><jats:sec><jats:title>RESULTS</jats:title><jats:p><jats:styled-content style="fixed-case">LC<jats:sub>50</jats:sub></jats:styled-content> values for two strains of <jats:italic>S. frugiperda</jats:italic> varied 6.6‐fold or 8.8‐fold over 17 generations. Storage time and humidity had no impact on <jats:styled-content style="fixed-case">Vip3Aa19</jats:styled-content> susceptibility, whereas prefeeding significantly reduced subsequent mortality (by 27%). Storage at reduced temperature increased mortality for one colony (from 45.6 to 73.0%) but not for the other. Introgression of field‐collected individuals affected susceptibility at the first generation but not for subsequent generations. A 24 h bioassay photophase significantly reduced susceptibility (by 26%) for both colonies.</jats:p></jats:sec><jats:sec><jats:title>CONCLUSION</jats:title><jats:p>Certain pretreatment and bioassay conditions were identified that can affect <jats:italic>S. frugiperda</jats:italic> <jats:styled-content style="fixed-case">Vip3Aa19</jats:styled-content> susceptibility, but innate larval heterogeneity was also present. Our observations should help to increase the consistency of insecticidal protein bioassay results. © 2015 Syngenta Crop Protection, LLC. <jats:italic>Pest Management Science</jats:italic> published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.</jats:p></jats:sec>