Progeny fitness determines the performance of the parasitoid Therophilus javanus, a prospective biocontrol agent against the legume pod borer

Published online: 26 Apr 2021Therophilus 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

Volatiles from Maruca vitrata (Lepidoptera, Crambidae) host plants influence olfactory responses of the parasitoid Therophilus javanus (Hymenoptera, Braconidae, Agathidinae)

Open Access Article; Published online: 9 Nov 2018.Plants damaged by herbivores are known to release odors attracting parasitoids. However, there is currently no information how leguminous plants damaged by the pod borer Maruca vitrata attract the exotic larval parasitoid Therophilus javanus, which was imported into Benin from the putative area of origin of the pod borer in tropical Asia for assessing its potential as a biological control agent. In this study, we used Y-tube olfactometer bioassays to investigate T. javanus response towards odors emitted by four M. vitrata-damaged host plants: cowpea Vigna unguiculata, the most important cultivated host, and the naturally occurring legumes Lonchocarpus sericeus, Sesbania rostrata and Tephrosia platycarpa. Olfactory attraction of T. javanus was influenced by the species of plant damaged by the pod borer. Moreover, odors released from M. vitrata-infested host plant organs (flowers and pods) were discriminated over non-infested organs in cowpea and T. platycarpa, respectively. These results are discussed in the context of the possible impact of M. vitrata host plants on T. javanus foraging activity and subsequent establishment in natural environments following experimental releases

Proteo-trancriptomic analyses reveal a large expansion of metalloprotease-like proteins in atypical venom vesicles of the wasp Meteorus pulchricornis (Braconidae)

Open Access Journal; Published online: 19 Jul 2021Meteorus pulchricornis (Ichneumonoidea, Braconidae) is an endoparasitoid wasp of lepidopteran caterpillars. Its parasitic success relies on vesicles (named M. pulchricornis Virus-Like Particles or MpVLPs) that are synthesized in the venom gland and injected into the parasitoid host along with the venom during oviposition. In order to define the content and understand the biogenesis of these atypical vesicles, we performed a transcriptome analysis of the venom gland and a proteomic analysis of the venom and purified MpVLPs. About half of the MpVLPs and soluble venom proteins identified were unknown and no similarity with any known viral sequence was found. However, MpVLPs contained a large number of proteins labelled as metalloproteinases while the most abundant protein family in the soluble venom was that of proteins containing the Domain of Unknown Function DUF-4803. The high number of these proteins identified suggests that a large expansion of these two protein families occurred in M. pulchricornis. Therefore, although the exact mechanism of MpVLPs formation remains to be elucidated, these vesicles appear to be “metalloproteinase bombs” that may have several physiological roles in the host including modifying the functions of its immune cells. The role of DUF4803 proteins, also present in the venom of other braconids, remains to be clarified