Field‐evolved resistance to chlorpyrifos by Spodoptera frugiperda (Lepidoptera: Noctuidae): Inheritance mode, cross‐resistance patterns, and synergism

Abstract

BACKGROUND: Fall armyworm (FAW), Spodoptera frugiperda (Smith), is an economically important pest worldwide. In this study, we selected a genotype of FAW resistant to chlorpyrifos from a field-collected population, characterized the genetic basis of resistance, and evaluated cross-resistance and mechanisms of resistance using synergists. RESULTS:The LD 50 values of chlorpyrifos for the resistant (Clorp-R) and susceptible (Sus) FAW genotypes were 24.26 and 0.023 ∼g per larva, respectively, representing a resistance ratio > 1050-fold. The LD 50 values of chlorpyrifos against heterozygotes were 3.34 and 4.00 ∼g per larva, suggesting that resistance is autosomally inherited. The chlorpyrifos resistance in FAW was influenced by few genes, with the minimum numbers of segregations being 1.74 and 1.88. On chlorpyrifos-sprayed plants and leaves, Clorp-R and heterozygote genotypes showed >95% and >52% survival, respectively, whereas the Sus genotype had no survival, indicating that the resistance is incompletely dominant at the field rate of chlorpyrifos. The Clorp-R genotype presented some cross-resistance to acephate, but low cross-resistance to thiodicarb, methomyl, chlorfenapyr, flubendiamide, methoxyfenozide, spinetoram, and teflubenzuron. The synergists piperonyl butoxide, diethyl maleate, and S,S,S-tributyl phosphorotrithiotate did not have relevant effects on the Clorp-R genotype, suggesting a minor role for metabolic resistance.CONCLUSIONS: The inheritance of chlorpyrifos resistance in FAW was characterized as autosomal, incompletely dominant, and polygenic, with metabolic resistance playing a small role in the detoxification of chlorpyrifos. Low cross-resistance between chlorpyrifos and other mode of action (MoA) insecticides occurs in FAW, highlighting the importance of considering the rotation of MoA as a strategy to delay resistance.

Monitoring Resistance and Biochemical Studies of Three Egyptian Field Strains of Spodoptera littoralis (Lepidoptera: Noctuidae) to Six Insecticides

“…The indiscriminate use of conventional and newer insecticides has caused the development of resistance to almost all kinds of insecticides in the Noctuidae species [ 7 , 12 , 13 , 38 , 39 , 40 , 41 ]. According to the Egyptian Agricultural Pesticides Committee, EAPC (2022), several groups of biochemical or chemical insecticides, such as organophosphorus, pyrethroids, insect growth regulators (IGRs), diamides, oxadiazin, spinosyns, emamectin benzoate and B. thuringiensis , are used for S. littoralis management.…”

“…Currently, S. littoralis is in the top 30 most resistant species in the world, according to the Arthropod Pesticide Resistance Database ( , accessed on 18 May 2021). Thus, other species, such as Spodoptera litura (Fabricius) [ 10 , 11 , 12 ], Spodoptera frugiperda (Smith) [ 13 ] and Spodoptera exigua (Hübner) [ 14 ], have developed resistance to a variety of insecticide groups due to long-term insecticide application.…”

Susceptibility monitoring and comparative gene expression of susceptible and resistant strains of Spodoptera frugiperda to lambda‐cyhalothrin and chlorpyrifos

“…59 Previous studies with FAW collected from an area with control failures by chlorpyrifos used synergist bioassays to indicate that detoxification metabolism played a minor role in resistance. 14 On the other hand, investigation using microarray sequencing of the RNA of S. frugiperda that was resistant and susceptible to lambda-cyhalothrin and chlorpyrifos demonstrated mutations on acetylcholinesterase and voltage-gated sodium channel genes, and the overexpression of detoxification enzymes (glutathione S-transferases, cytochrome P450s, and carboxylesterases) in the resistant strains was associated with S. frugiperda resistance mechanisms. 8 These studies allow us to infer that the resistance mechanisms of S. frugiperda to the insecticides lambdacyhalothrin and chlorpyrifos are complex and there can be several resistance mechanisms in a single population.…”

“…Unfortunately, their indiscriminate application contributed to the evolution of S. frugiperda resistance to several compounds of these two chemical groups 8,25 . High levels of resistance have been reported to the pyrethroids lambda‐cyhalothrin, permethrin, cyhalothrin, tralomethrin, bifenthrin, and fluvalinate, and to the organophosphates malathion, chlorpyrifos, methyl parathion, diazinon and sulprofos 8,14,25–27 …”

Fitness costs associated with spinetoram resistance inSpodoptera frugiperdais driven by host plants

“…The ability of this pest to explore different host plant species is one of the major factors of its success to colonize new areas. The control of S. frugiperda relies mainly on the use of chemical insecticides, but the extensive use of this control tactics resulted in resistance cases to many groups of insecticides (Diez-Rodríguez and Omoto 2001;Carvalho et al 2013;Nascimento et al 2016;Okuma et al 2018;Bolzan et al 2019;Lira et al 2020;Muraro et al 2021;Garlet et al 2021a), challenging the management of this pest.…”