The biocontrol agents of fall armyworm, Spodoptera frugiperda in Togo: moderating insecticide applications for natural control of the pest?

Abstract

Abstract Although there has been intensive use of insecticides for fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) management, their effects on population reduction and performance of natural enemies have not been adequately investigated. Therefore, this study assessed the diversity and performance of natural biocontrol agents under insecticide and insecticide-free applications. Bio-agents were annually collected from 2016 to 2022 in 348 maize farms throughout the West African nation of Togo. The collections included the entomopathogenic nematode Ovomermis sinensis (Nematoda: Mermithidae), unidentified bacteria from Enterobacteriaceae and Enterococcus, unidentified viruses from Ascoviruses and Baculoviruses, and fungi Isaria spp. (Hypocreales: Clavicipitaceae) and Metarhizium rileyi (Hypocreales: Cordycipitaceae). Eggs were parasitized by Telenomus remus (Hymenoptera: Platygastridae), and the egg-larval parasitoid Chelonus bifoveolatus (Hymenoptera: Braconidae). Larval parasitoids included Anatrichus erinaceus (Diptera: Chloropidae), Archytas spp. and Lespesiaspp. (Diptera: Tachinidae), Bracon sp., Coccygidium luteum, Cotesia icipe and Meteoridea testacea (Hymenoptera: Braconidae), and Campoletis grioti and Ophion spp. (Hymenoptera: Ichneumonidae). The collected predators included Orius insidiosus (Heteropterans: Anthocoridae), Haematochares obscuripennis, Peprius nodulipes, Rhynocoris sp. and Zelus renardii (Heteroptera: Reduviidae), Calleida sp. (Coleoptera: Carabidae), Cheilomenes sulphurea, Coccinella septempunctata and Cycloneda sanguinea (Coleoptera: Coccinellidae), Euborellia annulipes, Forficula auricularia and F. senegalensis (Dermaptera: Forficulidae), Pheidole megacephala and Polyrhachis lamellidens (Hymenoptera: Formicidae), Chrysoperla carnea (Neuroptera: Chrysopidae), and Mantis religiosa(Mantodea: Mantidae). The parasitism rates were from 14.72% in 2018 to 45.38% in 2022 for egg masses, and from 1.32% in 2016 to 41.85% in 2021 for larvae. The parasitism rates were three to four times higher in unsprayed farms than sprayed farms.