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bioRxiv · 10.1101/2020.06.27.171025

Performance of Bracon brevicornis (Wesmael) on two Spodoptera species and application as potential biocontrol agent against fall armyworm

Ghosh, E.·Varshney, R.·Venkatesan, R.
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Abstract

Successful pest management using parasitoids requires careful evaluation of host-parasitoid interactions. Here, we report the performance of larval ecto-parasitoid wasp, Bracon brevicornis (Wesmael) on important agricultural pests, Spodoptera litura (Fabricius) and S. frugiperda (J.E. Smith). Biology of B. brevicornis was studied on different host instars under laboratory and cage setup. In no-choice assay, the parasitoid development was highest on fifth instar S. litura larvae as the wasp laid ∼253 eggs with 62% hatching, 76% pupae formation and 78% adult emergence. Similarly, these parameters were highest on fifth instar S. frugiperda larvae (293 eggs, 57% hatching, 80% pupae formation, 70% adult emergence). In two-choice assay, B. brevicornis preferred fourth or fifth over third instar larvae of both hosts. Successful parasitism depends on host paralysis and suppression of host immunity. B. brevicornis interaction downregulated cellular immunity of both hosts as shown by reduced hemocyte viability and spreading. The percent parasitism rate of B. brevicornis was unaltered in the presence of host plant, Zea mays in cage study. 76 and 84% parasitism was observed on fifth instar larvae of S. litura and S. frugiperda, respectively. We evaluated the performance of B. brevicornis as a biocontrol agent on S. frugiperda in maize field. Our results show 54% average reduction in infestation after release of B. brevicornis. Taken together, we report the performance of B. brevicornis on important insect pests for the first time in laboratory and field conditions. Our findings indicate that B. brevicornis is a promising candidate for integrated pest management.Key messagesWe have evaluated the instar preference and performance of B. brevicornis as a potential biocontrol agent for two serious pests, Spodoptera litura and S. frugiperda.Fifth instar larva was most suitable for B. brevicornis development irrespective of the host species. B. brevicornis attack induced permanent paralysis and down-regulated cellular immunity of both hosts.Our field experiment confirmed B. brevicornis as a promising parasitoid for controlling S. frugiperda, a highly invasive pest of growing concern.Competing Interest StatementThe authors have declared no competing interest.View Full Text

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Ghosh, E., Varshney, R., Venkatesan, R.. 2020-06-29. Performance of Bracon brevicornis (Wesmael) on two Spodoptera species and application as potential biocontrol agent against fall armyworm. https://doi.org/10.1101/2020.06.27.171025

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