Therophilus javanus (Bhat & Gupta) is an exotic larval endoparasitoid newly imported from Asia into Africa as a classical biological control agent against the pod borer Maruca vitrata (Fabricius). The parasitoid preference for the five larval instars of M. vitrata and their influence on progeny sex ratio were assessed together with the impact of larval host age at the time of oviposition on development time, mother longevity and offspring production. In a choice situation, female parasitoids preferred to oviposit in the first three larval instars. The development of immature stages of the parasitoid was observed inside three-day-old hosts, whereby the first two larval instars of T. javanus completed their development as endoparasites and the third larval instar as ectoparasite. The development time was faster when first larval instars (two- and three-day-old) of the host caterpillars were parasitized compared to second larval instar (four-day-old). The highest proportion of daughters (0.51) was observed when females were provided with four-day-old hosts. The lowest intrinsic rate of increase (r) (0.21 ± 0.01), the lowest rate of increase (λ) (1.23 ± 0.01), and the lowest net reproductive rate (Ro) (35.93 ± 6.51) were recorded on four-day-old hosts. These results are discussed in the light of optimizing mass rearing and release strategies.

We thank the Cooperation and Cultural Action Service (SCAC) of the French Embassy in Cotonou for partial support of DAS (N 898392E). Co-funding was also provided by the CGIAR Research Program on Grain Legumes and Dryland Cereals (GLDC) (DAS, MT and BRP), and the Bill and Melinda Gates Foundation (BMGF) for partial co-funding of the study (OPP1082463 to MT and BRP) and Open Access publication support. We also thank Georg Goergen for the habitus illustration of T. javanus, and Basile Dato for technical ...

https://dx.doi.org/10.1038/s41598-021-88644-3

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Manuele Tamòhttps://orcid.org/0000-0002-5863-7421

https://dx.doi.org/10.1038/s41598-021-88644-3

Plant Production and Health

Agronomy; Cowpea; Disease Control; Grain Legumes; Plant Breeding; Plant Diseases; Plant Health; Plant Production

Biological Control; Biological Control Agents; Maruca Vitrata; Cowpeas; Plant Diseases; Plant Production; Plant Health; Progeny; Legumes

Africa; West Africa

Benin (Dahomey)

Headquarters and Western Africa Hub

Scientific Reports