Impact of Spodoptera frugiperda neonate pretreatment conditions on Vip3Aa19 insecticidal protein activity and laboratory bioassay variation

Authors

Karen F. Da Silva, University of Nebraska-LincolnFollow
Terence A. Spencer, University of Nebraska-Lincoln
Carolina Camargo Gil, University of Nebraska-LincolnFollow
Blair D. Siegfried, University of Nebraska-LincolnFollow
Frederick S. Walters, Syngenta Crop ProtectionFollow

ORCID IDs

Carolina Camargo Gil

Blair D. Siegfried

Document Type

Article

Date of this Version

2015

Citation

Pest Manag Sci 2016; 72: pp. 837–844, DOI 10.1002/ps.4175.

Comments

Copyright © 2015 Syngenta Crop Protection, LLC. Used by permission.

Abstract

BACKGROUND: 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 Spodoptera frugiperda (J.E. Smith) susceptibility to Vip3Aa19 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.

RESULTS: LC₅₀ values for two strains of S. frugiperda varied 6.6-fold or 8.8-fold over 17 generations. Storage time and humidity had no impact on Vip3Aa19 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.

CONCLUSION: Certain pretreatment and bioassay conditions were identified that can affect S. frugiperda Vip3Aa19 susceptibility, but innate larval heterogeneity was also present. Our observations should help to increase the consistency of insecticidal protein bioassay results.