Watermelon-infesting Tephritidae fruit fly guild and parasitism by Psyttalia phaeostigma (Hymenoptera: Braconidae)

Babatoundé Ferdinand Rodolphe Layodé,Miriam Frida Karlsson,Alexis Onzo

doi:10.1007/s42690-019-00066-x

Abstract

An ecological guild of Tephritidae fruit flies exploits cucurbit vegetable fruits, tremendously reducing their production worldwide. Knowledge of the composition of the guild of infesting flies in the field and information on their natural enemy species, might improve pest management strategies. Our aim was therefore to identify Tephritidae species infesting the watermelon Citrullus lanatus (Thunb.) Matsum. & Nakai in the Republic of Benin. Morphological and molecular identification of parasitoid species present in the field collections was also done. Infested watermelons were sampled in one of the main watermelon-production areas in the country. Adult tephritid flies emerging from watermelons were identified as Dacus bivittatus (Bigot), D. ciliatus Loew, D. punctatifrons Karsch, D. vertebratus Bezzi, Zeugodacus cucurbitae (Coquillet), and Ceratitis cosyra (Walker). In this study period, D. vertebratus was consistently the most abundant species emerging from watermelon. Dacus ciliatus was the second most common species followed by Z. cucurbitae. The number of emerging fruit flies per kilogram of watermelon varied with collection date and month, and was most variable for D. vertebratus. Parasitism in the fruit flies was 1.6 ± 6.4% and occurred through one wasp species that was identified as Psyttalia phaeostigma Wilkinson (Hymenoptera: Braconidae). This solitary parasitoid is closely related to other members of the P. concolor species complex, some of which are used in biological control. Problems associated with identifying Psyttalia species and possibility of using this wasp as a biological control agent against tephritid flies were discussed.

Highlights

The composition of insect pest species infesting agricultural crops is a result of the interaction of the pest with the host, the environment, other pests, their natural enemies, and their host spectra (Wyckhuys et al 2012; Parisey et al 2016; Charlery de la Masselière et al 2017)
The species D. bivittatus, D. ciliatus, D. punctatifrons, D. vertebratus, D. frontalis, and D. lounsburyii are indigenous to Africa (De Meyer and Ekesi 2016), while Z. cucurbitae may have arrived from Asia at the beginning of the 1900
The fore, mid and hind femurs of D. vertebratus are dark in the apical half, which differentiates it from D. frontalis which was only dark on the apical mid femur

Summary

Introduction

The composition of insect pest species infesting agricultural crops is a result of the interaction of the pest with the host, the environment, other pests, their natural enemies, and their host spectra (Wyckhuys et al 2012; Parisey et al 2016; Charlery de la Masselière et al 2017). Records on watermelon infestation from West Africa are scarce. Gnanvossou et al (2008) reported D. vertebratus as the dominant species in Benin, representing 80% of the tephritid guild, while in Ghana, Bactrocera dorsalis, Z. cucurbitae, and D. bivittatus were reported as the dominant fruit fly species infesting watermelon (Badii et al 2015). The species D. bivittatus, D. ciliatus, D. punctatifrons, D. vertebratus, D. frontalis, and D. lounsburyii are indigenous to Africa (De Meyer and Ekesi 2016), while Z. cucurbitae may have arrived from Asia at the beginning of the 1900. The introduction of Z. cucurbitae is suspected to influence the African guild of watermelon-infesting tephritid species, since it is considered an invasive species that could out-compete native species (Vayssières et al 2002; Mwatawala et al 2010). Watermelon production is increasingly important in West Africa (Fatondji et al 2008). It is important to investigate more sustainable alternative control approaches against these pests

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