Efficacy of Metarhizium anisopliae and Spinetoram against Fall Armyworm (Spodoptera frugiperda) on Maize in Southern Benin

African Journal of Agriculture | Vol. 13, No. 8, August 2026 | pp. 146–153

DOI: 10.46882/2026/AJA/000752

Article Type: Original Research Article

Title: Efficacy of Metarhizium anisopliae and Spinetoram against Fall Armyworm (Spodoptera frugiperda) on Maize in Southern Benin

Names of Authors: Sègbégnon G. Agbovi¹, Cossi J. Tossou¹, Albert O. Gbaguidi²

Authors’ Affiliations: ¹Institut National des Recherches Agricoles du Bénin (INRAB), Cotonou, Benin; ²Université d'Abomey-Calavi, Faculté des Sciences Agronomiques, Cotonou, Benin

Abstract: The invasive fall armyworm (Spodoptera frugiperda J.E. Smith) causes continuous defoliation damage in West African maize fields. Heavy reliance on broad-spectrum synthetic chemical pesticides creates pesticide resistance risks and endangers beneficial field organisms. This study evaluated the comparative field efficacy of the entomopathogenic fungus Metarhizium anisopliae (strain ICIPE 7) and the bio-insecticide Spinetoram, individually and in rotation, against S. frugiperda larvae. Field trials used a randomized block setup with four replicates per treatment. Treatments included: M. anisopliae alone (2.0 x 10¹² spores/ha), Spinetoram alone (250 mL/ha), an alternating rotation of M. anisopliae and Spinetoram, and an untreated control. Larval populations and leaf damage scores were recorded at 3, 7, and 14 days post-application. The results revealed that Spinetoram alone achieved the fastest knockdown effect, cutting larval counts by 88.5% within 3 days. However, the alternating rotation treatment (M. anisopliae followed by Spinetoram) provided the most durable protection, keeping leaf leaf damage below 12.0% across the whorl development stage. This rotational treatment limited final grain yield loss to just 4.2% compared to a 38.6% yield collapse in the untreated control plots. Integrating M. anisopliae with targeted Spinetoram applications offers a highly effective strategy to control fall armyworm while mitigating chemical resistance risks.

Keywords: Spodoptera frugiperda, Metarhizium anisopliae, Spinetoram, Larval mortality, Integrated pest management, Yield protection

Manuscript Timeline: Received: June 11, 2026; Revised: July 15, 2026; Accepted: August 06, 2026; Published: August 31, 2026

Citation: Agbovi, S. G., Tossou, C. J., & Gbaguidi, A. O. (2026). Efficacy of Metarhizium anisopliae and Spinetoram against Fall Armyworm (Spodoptera frugiperda) on Maize in Southern Benin. African Journal of Agriculture, 13(8), 146–153. DOI: 10.46882/2026/AJA/000752

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