Susceptibility and Aversion of <I>Spodoptera frugiperda</I> (Lepidoptera: Noctuidae) to Cry1F Bt Maize and Considerations for Insect Resistance Management

Abstract

Bacillus thuringiensis (Bt) maize was developed primarily for North American pests such as European corn borer (Ostrinia nubilalis (Hübner)). However, most Bt maize products are also cultivated outside of North America, where the primary pests may be different and may have lower susceptibility to Bt toxins. Fall armyworm (Spodoptera frugiperda JE Smith) is an important pest and primary target of Bt maize in Central and South America. S. frugiperda susceptibility to Cry1F (expressed in event TC1507) is an example of a pestby-toxin interaction that does not meet the high-dose definition. In this study, the behavioral and toxic response of S. frugiperda to Cry1F maize was investigated by measuring the percentage of time naïve third instars spent feeding during a 3-min exposure. S. frugiperdaalso were exposed as third instars to Cry1F maize for 14 d to measure weight gain and survival. S. frugiperda demonstrated an initial, postingestive aversive response to Cry1F maize, and few larvae survived the 14 d exposure. The role of susceptibility and avoidance are discussed in the context of global IRM refuge strategy development for Bt products. TC1507) is an example of a pest-by-toxin interaction that does not meet the high-dose deÞnition. In this study, the behavioral and toxic response of S. frugiperda to Cry1F maize was investigated by measuring the percentage of time naṏve third instars spent feeding during a 3-min exposure. S. frugiperda also were exposed as third instars to Cry1F maize for 14 d to measure weight gain and survival. S. frugiperda demonstrated an initial, postingestive aversive response to Cry1F maize, and few larvae survived the 14 d exposure. The role of susceptibility and avoidance are discussed in the context of global IRM refuge strategy development for Bt products.

Functional dominance of different aged larvae of Bt-resistant Spodoptera frugiperda (Lepidoptera: Noctuidae) on transgenic maize expressing Vip3Aa20 protein

“…Number and fitness of susceptible insects produced from refuge plants, adult mating, dispersion, and oviposition are additional aspects that may also be considered before adoption of the blended refuge strategy (Binning et al, 2014). According to ours results, if Vip-R larvae move among Bt and non-Bt maize plants, survival will be high and similar in these plants, independently of the age.…”

“…In contrast, the survival of heterozygote and Sus strains in later instars was probably due to the short time available to ingest a sufficient amount of Bt protein(s) to cause mortality before pupal stage. The survival of FAW in last instars was also reported on Cry1Ac/Cry1F-cotton (Gossypium hirsutum L.) (Sorgatto et al, 2015) and Cry1F-maize (Binning et al, 2014). Survival of advanced instars was also documented for Heliothis virescens (F.) (Jenkins et al, 1993), Helicoverpa zea (Boddie) (Halcomb et al, 1996), and Chrysodeixis includens (Walker) (Ashfaq et al, 2001) on Cry1Ac-cotton.…”

“…Several studies also demonstrated that the feeding and/or behavior mobility of larvae is different between Bt and non-Bt plants. According to Binning et al (2014), FAW at third instar showed an aversion response to Cry1F-maize, without consuming a lethal dose before rejection occurs. Neonates of Helicoverpa armigera Hübner and Alabama argillacea Hübner, in the presence of the Cry1Ac protein expressed on cotton, increase the dispersion from Bt to non-Bt plants (Zhang et al, 2004;Ramalho et al, 2014).…”

“…Mortality data until adult stage were used to estimate the dominance (D) of resistance using the method described by Bourguet et al (2000) based on the following equation:…”

Attack and defense movements involved in the interaction of Spodoptera frugiperda and Helicoverpa zea (Lepidoptera: Noctuidae)

“…Insects which feed on Bt transgenic crops might be negatively affected during their development, and in consequence, be smaller than those that feed on non-Bt plants. This would lead to the consequence of the larval intraguild interaction Binning et al 2014). The continuous release of hybrids expressing different endotoxins has also stimulated research on larval behavior.…”