Inhibition of electrophysiological response to the pheromone of the fall armyworm, Spodoptera frugiperda

Abstract

In the search for new control methods for the fall armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), we present the inhibition of the electroantennographic (EAG) response to the pheromone by 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP). As a member of the trifluoromethyl ketones, OTFP is a potent inhibitor of serine esterases, particularly those of insect antennae. Exposure of antennal receptors to OTFP vapors resulted in a decreased amplitude and 2/3 repolarization time (2/3 RT) of the EAG response to the pheromone. The effect was reversible, with the amplitude and repolarization time being recovered upon suppression of the treatment. The non-fluorinated analogue 3-octhylthiopropan-2-one (OTP) did not affect either the amplitude or the 2/3 RT of the EAG response to the pheromone, confirming the key role played by fluorine atoms in this type of chemical. These results may be the basis for new behavioral studies with the aim of considering OTFP in future management strategies of the FAW.

Synthesis of allylic trifluoromethyl ketones and their activity as inhibitors of the sex pheromone of the leopard moth, Zeuzera pyrina L. (Lepidoptera: Cossidae)

“…Pheromone inhibitors, as analogues of the natural pheromones, have been used in mating disruption experiments for pest control 43. The present authors have demonstrated in recent years that TFMKs are potent antagonists of the pheromone in the field and good inhibitors in electrophysiology and behaviour in the laboratory 16, 17, 38–42. In addition, although it has not been determined in antennal extracts of Z. pyrina , these chemicals displayed a remarkable antiesterase activity in S. littoralis ,11, 14 S. nonagrioides 44 and O. nubilalis.…”

“…Similar results were obtained on Spodoptera littoralis Boisduval, where 3‐octylthio‐1,1,1‐trifluoropropan‐2‐one (OTFP) decreased the EAG amplitude and increased the repolarisation time of the pheromone response, the EAG kinetics being increased with the TFMK dose 38. Also, exposure of antennal receptors of Spodoptera frugiperda (JE Smith) to vapours of OTFP resulted in a decreased amplitude and 2/3 repolarisation time of the EAG response to the pheromone, the effect being reversible 39. The non‐fluorinated analogue (OTP) did not affect any of the EAG parameters, confirming the key role played by fluorine atoms in this type of chemical 39, 40.…”

“…Also, exposure of antennal receptors of Spodoptera frugiperda (JE Smith) to vapours of OTFP resulted in a decreased amplitude and 2/3 repolarisation time of the EAG response to the pheromone, the effect being reversible 39. The non‐fluorinated analogue (OTP) did not affect any of the EAG parameters, confirming the key role played by fluorine atoms in this type of chemical 39, 40. In the European corn borer Ostrinia nubilalis (Hübner), the TFMK analogue of the major component of the pheromone inhibited the EAG response to the natural attractant in a dose–response manner, and 10 pg of the ketone was sufficient to promote a 77% inhibition response 40…”

Hymenopteran parasitoids of fall armyworm (Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)) in Australia, with the description of five new species in the families Braconidae and Eulophidae

“…Chelonus trojanus can be diagnosed from the following species of Chelonus reared from S. frugiperda outside of Australia: From C. cautus Cresson, 1872 (reared from S. frugiperda in Mexico (Gutiérrez‐Ramírez et al 2015), C. curvimaculatus Cameron, 1906 (reared from S. frugiperda in Kenya and Zambia (several records, collated in Li et al 2023), and from C . nr blackburni (sensu rearing record from India and figure in Sagar et al, (2022), by not having a solid white band in the anterior quarter of the metasoma. From C. antillarum Marshall 1885 (reared from S. frugiperda in Barbados and Nicaragua (Molina‐Ochoa et al 2004) by fore wing vein 2‐SR being approximately 1.3 × longer than vein 3‐SR; in C. antellarum , 2‐SR is almost 2 × longer than 3‐SR (based on specimens in the Waite Insect and Nematode Collection, reared from Spodoptera sp.…”

“…There have been close to 100 hymenopteran parasitoid species reared from S. frugiperda across the globe, with high diversity from the families Braconidae and Ichneumonidae, and the superfamily Chalcidoidea (Agboyi et al 2020; Ashley 1986; García‐González, Rios‐Velasco, & Iglesias‐Pérez 2020; Gutiérrez‐Ramírez et al 2015; Li et al 2023; Meagher et al 2016; Molina‐Ochoa et al 2003, 2004; Murúa, Molina‐Ochoa, & Fidalgo 2009; Otim et al 2021; Sagar et al 2022; Serrano‐Domínguez et al 2021; Youssef 2021). Of the species recorded overseas, only Cotesia ruficrus (Haliday), Telenomus remus Nixon, and Trichogramma pretiosum Riley are known to already occur in Australia.…”