Insects 2022, 13, 688. https://doi.org/10.3390/insects13080688 www.mdpi.com/journal/insects Article Live Drosophila Melanogaster Larvae Deter Oviposition by Drosophila suzukii Trisna D. Tungadi 1 , Bethan Shaw 1 , Glen Powell 2 , David R. Hall 3 , Daniel P. Bray 3 , Steven J. Harte 3 , Dudley I. Farman 3 , Herman Wijnen 4 and Michelle T. Fountain 1, * 1 NIAB, East Malling, Kent ME19 6BJ, UK; trisnat@gmail.com (T.D.T.); bethan.shaw@niab.com (B.S.) 2 RHS Garden Wisley, Woking, Surrey GU23 6QB, UK; glenpowell@rhs.org.uk 3 Natural Resources Institute, University of Greenwich, Southampton ME4 4TB, UK; d.r.hall@greenwich.ac.uk (D.R.H.); d.bray@greenwich.ac.uk (D.P.B.); s.j.harte@greenwich.ac.uk (S.J.H.); d.i.farman@greenwich.ac.uk (D.I.F.) 4 School of Biological Sciences and Institute for Life Sciences, University of Southampton, Southampton SO17 1BJ, UK; h.wijnen@soton.ac.uk * Correspondence: michelle.fountain@niab.com Simple Summary: The invasive insect pest, Drosophila suzukii Matsumura or spotted-wing drosoph- ila (SWD) lays its eggs in soft and stone fruit. Eggs hatch into larvae, which feed on fruit, causing fruit collapse and significant economic losses worldwide. Current control methods rely primarily on foliar insecticide applications, which are not sustainable long-term solutions. In nature, D. suzukii interacts with and encounters other Drosophila species, especially towards the end of the growing season when ripening fruits are scarce. We showed previously that D. suzukii were deterred from laying eggs on artificial media exposed to egg laying Drosophila melanogaster, its sister species. It was hypothesized that a signal was left by D. melanogaster which deterred D. suzukii from laying eggs. This study aimed to identify from which D. melanogaster life stage the egg laying deterrent signal originated and we showed that the presence of live D. melanogaster larvae on the egg laying media deter D. suzukii from laying eggs. Drosophila melanogaster cuticular hydrocarbons were examined as the signal source, but no evidence was found for their involvement. These results have improved our understanding of the interspecific interactions between D. suzukii and other Drosophila species and could provide new innovative approaches to D. suzukii management strategies. Abstract: The worldwide invasive insect pest, Drosophila suzukii Matsumura (spotted-wing Drosoph- ila), lays eggs in soft and stone fruit before harvest. Hatched larvae cause fruit collapse and signifi- cant economic losses. Current control methods rely primarily on foliar insecticide applications, which are not sustainable long-term solutions due to regulatory restrictions and the risk of insecti- cide resistance developing. We showed before that D. suzukii were deterred from laying eggs on artificial media previously visited by its sister species—Drosophila melanogaster. In the current study, laboratory choice test experiments were conducted to identify which D. melanogaster life stage (eggs, larvae, or adult) deterred D. suzukii oviposition. We demonstrated that the presence of live D. mel- anogaster larvae on the egg-laying media consistently deterred D. suzukii oviposition. Drosophila mel- anogaster cuticular hydrocarbons (CHCs) were examined as candidate for the oviposition deterrent. CHCs of larval and adult D. melanogaster and D. suzukii were analyzed. In both species, the compo- sition of the CHCs of larvae was similar to that of adults, although quantities present were much lower. Furthermore, the CHC profiles of the two species were markedly different. However, when assayed as deterrents in the laboratory choice test experiment, CHC extracts from D. melanogaster did not deter oviposition by D. suzukii. Keywords: drosophilidae; integrated pest management; interspecific interactions; push-pull; sopho- phora; repellent; avoidance; behaviour; drosophila Citation: Tungadi, T.D.; Shaw, B.; Powell, G.; Hall, D.R.; Bray, D.P.; Harte, S.J.; Farman, D.I.; Wijnen, H.; Fountain, M.T. Live Drosophila Mel- anogaster Larvae Deter Oviposition by Drosophila suzukii. Insects 2022, 13, 688. https://doi.org/10.3390/ insects13080688 Academic Editor: George N. Mbata Received: 11 July 2022 Accepted: 26 July 2022 Published: 29 July 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).