Bracon wasps for ecological pest control-a laboratory experiment.

Jessica Lettmann,Karsten Mody,Tore-Aliocha Kursch-Metz,Katja Wehner,Nico Blüthgen

doi:10.7717/peerj.11540

Jessica Lettmann, Karsten Mody + Show 3 more

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https://doi.org/10.7717/peerj.11540

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Abstract

Biological control of pest insects by natural enemies may be an effective, cheap and environmentally friendly alternative to synthetic pesticides. The cosmopolitan parasitoid wasp species Bracon brevicornis Wesmael and B. hebetor Say (Hymenoptera: Braconidae) use lepidopteran species as hosts, including insect pests like Ephestia kuehniella or Ostrinia nubilalis. Here, we compare the reproductive success of both Bracon species on E. kuehniella in a laboratory experiment. We asked (1) how the reproductive success on a single host larva changes with temperature, (2) how it changes with temperature when more host larvae are present and (3) how temperature and availability of host larvae influence the efficacy of Bracon species as biological control agents. In general, differences between B. brevicornis and B. hebetor have been small. For rearing both Bracon species in the laboratory on one host larva, a temperature between 20–27 °C seems appropriate to obtain the highest number of offspring with a female-biased sex ratio. Rearing the braconid wasps on more than one host larva revealed a higher number of total offspring but less offspring per host larva on average. Again, highest numbers of offspring hatched at 27 °C and the sex ratio was independent from temperature. Although no parasitoids hatched at 12 °C and only few at 36 °C, host larvae were still paralyzed. The efficacy of B. brevicornis was higher than 80% at all numbers of host larvae presented at all temperatures while the efficacy of B. hebetor was less than 80% at 12 °C and 27 °C at low numbers of host larvae presented. In conclusion, practitioners can use either B. brevicornis or B. hebetor at low and high temperatures and at varying host densities to achieve high pest control efficacy.

Highlights

Intensified land-use often causes a loss of biodiversity of above- and below-ground organisms and a homogenization of plant and animal communities by the reduction of habitat diversity or habitat destruction (Andow, 1983; Hendrickx et al, 2007; Weiner et al, 2011; Allan et al, 2015; Newbold et al, 2015; Chisté et al, 2016; Gossner et al, 2016)
How does the reproductive success of female wasps of B. brevicornis and B. hebetor on a single host larva change with temperature?
How does the reproductive success of female wasps of B. brevicornis and B. hebetor on a single host larva change with temperature? While presenting one host larva to one female wasp in our study, B. hebetor produced slightly higher numbers of offspring compared to B. brevicornis and oviposition was reduced by increasing temperature

Summary

Introduction

Intensified land-use often causes a loss of biodiversity of above- and below-ground organisms and a homogenization of plant and animal communities by the reduction of habitat diversity or habitat destruction (Andow, 1983; Hendrickx et al, 2007; Weiner et al, 2011; Allan et al, 2015; Newbold et al, 2015; Chisté et al, 2016; Gossner et al, 2016). Such losses of biodiversity affect ecosystem services; e.g., the loss of pollinator species such as wild bees or bumblebees causes a reduction in pollination Natural enemies like the insidious flower bug Orius insidiosus (Say) (Hemiptera: Anthocoridae) or parasitoid wasps are less abundant in monocultures than in diverse landscapes (Lundgren, Wyckhuys & Desneux, 2009; Pak et al, 2015)

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