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Temperature Affects Biological Control Efficacy: A Microcosm Study of Trichogramma achaeae

Authors
  • Chen, Long1, 2
  • Enkegaard, Annie1
  • Sørensen, Jesper Givskov2
  • 1 (A.E.)
  • 2 Department of Biology, Aarhus University, 8000 Aarhus, Denmark
Type
Published Article
Journal
Insects
Publisher
MDPI AG
Publication Date
Jan 22, 2021
Volume
12
Issue
2
Identifiers
DOI: 10.3390/insects12020095
PMID: 33499426
PMCID: PMC7912409
Source
PubMed Central
Keywords
Disciplines
  • Article
License
Green

Abstract

Simple Summary The performance of biological control agents (BCAs) under field conditions is of importance to successfully suppress pests following release. However, the quality of BCAs is usually evaluated with laboratory measurements under controlled conditions, which has been shown unable to predict the performance in complex field conditions. In this study, we quantified the quality of the parasitoid Trichogramma achaeae in microcosms at four constant temperatures and evaluated its ability to locate and parasitise pest eggs. We also compared parasitisation efficiency with fecundity as determined under laboratory conditions. We found the biological control efficacy as determined in our microcosms was strongly regulated by temperature and was unlikely to be predicted by laboratory fecundity. These findings suggest that more complex assays, including behavioural responses, might be developed to demonstrate the field quality of BCAs. Abstract Current quality control of mass-reared biological control agents (BCAs) is usually performed in the laboratory and often fails to include behavioural aspects of the BCAs. As a result, the use of efficacy measurements determined solely under laboratory conditions to predict field efficacy can be questioned. In this study, microcosms were designed to estimate biological control efficacy (realised parasitisation efficiency) of Trichogramma achaeae Nagaraja and Nagarkatti (Hymenoptera: Trichogrammatidae) parasitising Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs across the operational temperature range (15–30 °C). Temperature greatly affected the success of females in finding and parasitising E. kuehniella eggs, with parasitisation being reduced at 15 and 20 °C, as both the percentage of parasitised host eggs and the percentage of leaves per plant with parasitised host eggs decreased sharply compared with higher temperatures. Graphing previous data on laboratory fecundity against parasitisation efficiency shows that the laboratory-measured fecundity of T. achaeae was unlikely to predict field efficacy across temperatures. Results also showed that leaf side had no effect on the preference of T. achaeae in parasitising E. kuehniella eggs; however, T. achaeae preferred to lay their eggs on the top tier of plants. These findings suggest that more complex assays, which include behavioural responses, might be developed for optimised quality control of BCAs intended for field application.

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