Abstract
Simple SummaryFall armyworm (FAW), Spodoptera frugiperda, was reported in Cameroon for the first time in 2017 and by the end of 2018; the pest was found all over the country. Cameroon is among the first countries in Africa where the southern armyworm (SAW), Spodoptera eridania, another economical important armyworm was reported. The African governments adopted emergency actions around chemical insecticides despite the range of economic and health risks associated with chemical control. This work aims at identifying parasitoids (natural enemies) of armyworms and test their acceptability, suitability, and host range on Spodoptera spp., that can play a significant role in the sustainable management of these spodopterans. Field surveys conducted lead to the identification of two egg and four larval parasitoids. The fall armyworm was the predominant spodopteran. Laboratory studies were conducted to assess the performance of parasitoids associated with both pests in Cameroon. T. remus showed significantly higher parasitism on FAW than SAW, with significantly shorter development time on FAW, while inducing significant non-reproductive mortality on FAW. Laboratory performance of larval parasitoid was not compared between the two spodopterans identified but the developmental parameters showed that C. icipe has a shorter development time compared to other larval parasitoids.Fall armyworm (FAW) Spodoptera frugiperda (J.E. Smith) and southern armyworm (SAW) Spodoptera eridania (Stoll) have become major threats to crops in Africa since 2016. African governments adopted emergency actions around chemical insecticides, with limited efforts to assess the richness or roles of indigenous natural enemies. Field surveys and laboratory studies were conducted to identify and assess the performance of parasitoids associated with spodopterans in Cameroon. FAW was the most abundant spodopteran pest. Telenomus remus (Nixon), Trichogramma chilonis (Ishi), Charops sp. (Szépligeti), Coccygidium luteum (Cameron), Cotesia icipe (Fernandez & Fiaboe), and Cotesia sesamiae (Cameron) are the first records in the country on spodopterans. Telenomus remus, T. chilonis, C. icipe, and Charops sp. were obtained from both FAW and SAW; C. luteum and C. sesamiae from FAW. The distribution of spodopterans, their endoparasitoids, and parasitism rates varied with host, season and location. In the laboratory, T. remus showed significantly higher parasitism on FAW than SAW, and significant differences in the development parameters between the two host eggs, with shorter development time on FAW. It induced significant non-reproductive mortality on FAW but not on SAW. Developmental parameters showed that C. icipe has a shorter development time compared to other larval parasitoids. Implications for conservative and augmentative biocontrol are discussed.
Highlights
Spodoptera Guenée (Lepidoptera: Noctuidae) is a genus that comprises 31 species [1,2]
A report by Montezano et al (2018) indicated that fall armyworm is a polyphagous pest with a host range of about 353 recorded plant species in 76 families, whereas S. eridania was reported on 202 host plants species from 58 families [2]
We discovered for the first time in Cameroon various parasitoids associated with the new invasive spodopteran pests under various agro-ecological zones
Summary
Spodoptera Guenée (Lepidoptera: Noctuidae) is a genus that comprises 31 species [1,2] Species from this genus are commonly known as armyworms among which eight have been reported in Africa since the 1970s [3]. Smith) and southern armyworm (SAW) S. eridania (Stoll), have recently invaded Africa and causing havoc since 2016 [6,7] Among these armyworms, only S. frugiperda is reported to feed on both monocots and dicots [8], with a host range of about 353 recorded plant species in 76 families [9]. SAW distribution, population genetics, and damage in the country and the continent, in general, has not been assessed, it occurs throughout the Americas, and has been reported on 202 host plant species from 58 families [13]
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