Mogadingoane, Keitumetse Neo2025-06-182024-11Mogadingoane, Keitumetse Neo. (2024). Comparison of different bioassay methods for the assessment of dose-response relationships of entomopathogens and toxins against Helicoverpa armigera (Hübner, 1809) (Lepidoptera: Noctuidae). [Master's dissertation, University of the Witwatersrand, Johannesburg]. WIReDSpace. https://hdl.handle.net/10539/45161https://hdl.handle.net/10539/45161A dissertation submitted in fulfilment of the requirements for the degree Master of Science, to the Faculty of Science, School of in Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, 2024.Bioassays are an important tool for developing bioinsecticides against agricultural pests. The aim of this study was to compare two bioassay methods – diet overlay and droplet feeding – to identify the most suitable method for assessing dose-response relationships of entomopathogens and toxins against second instar larvae of Helicoverpa armigera. The toxins used were purified Bacillus thuringiensis Cry1A.105 and Cry2Ab2.820 proteins, the spore-crystal complex (SCC) of B. thuringiensis subspecies kurstaki strain HD-73, and the entomopathogen Helicoverpa armigera nucleopolyhedrovirus (HearNPV). Based on the heterogeneity factor, coefficient of variance (CV) and relative precision, the diet overlay bioassay was determined to be the best fit for use with HD-73 SCC and HearNPV. Suitable bioassay methods could not be determined for the purified B. thuringiensis proteins due to a poor probit model fit and low precision of estimated LC50s and LD50s. Validation of CV and relative precision across bioassays will ensure the most suitable methods are used for sustainable integrated pest management.en©2024 University of the Witwatersrand, Johannesburg. All rights reserved. The copyright in this work vests in the University of the Witwatersrand, Johannesburg. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of University of the Witwatersrand, Johannesburg.BioassaysHelicoverpaDose-responseUCTDDissertationUniversity of the Witwatersrand, JohannesburgSDG-3: Good health and well-beingSDG-9: Industry, innovation and infrastructure