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dc.contributor.authorThornham, Daniel Georgeen
dc.date.accessioned2018-05-14T10:16:43Z
dc.date.available2018-05-14T10:16:43Z
dc.date.issued2006en
dc.identifier.urihttp://hdl.handle.net/1842/30025
dc.description.abstracten
dc.description.abstractA review of the scientific literature identified the need to examine sub-lethal behavioural effects of a range of insecticides on one of the most important and widely used groups of arthropods in biological control, the ladybirds (Chapter 1). The aphidophagous seven-spotted ladybird, Coccinellci septempunctata was identified as being an ideal model. Culture methods were developed from existing protocols for both the predator and two species of prey, Acyrthosiphon pisum and Myzus persicae, before using pesticide usage survey reports to identify insecticides that would provide the study with the broadest relevance to agriculturists (Chapter 2). Safe and effective spraying protocols were established using equipment which was assessed for its effectiveness and evenness of spray deposition (Chapter 2).en
dc.description.abstractThe locomotory behavioural responses of C. septempunctata to the insecticides and their active ingredients were examined in experimental, controlled environment arenas using video analysis software (Chapter 3). Experimental blocking enabled the behavioural responses to a variety of spray conditions to be directly compared, revealing a graded and consistent response to the insecticide residues. The pirimicarb-based insecticide, Aphox™, had the least effect on both locomotor behaviour and mortality, such that no significant differences between this treatment and water controls were recorded in either respect. The X-cyhalothrin-based insecticide, Hallmark with Zeon Technology™, had the greatest effect on locomotor behaviour, causing the coccinellids to reduce their overall movement over the three hours of the tests but the effect on mortality was minimal. The second pyrethroid tested, the cypermethrin-based Toppel 10™, drew similar responses from C. septempunctata that were only marginally less pronounced than those of Hallmark. The organophosphate insecticides, the chlorpyrifos-based Dursban 75WG™ and the dimethoate based BASF Dimethoate 40™, had limited but significant effects on aspects of the coccinellids' locomotor behaviour and caused significant mortality. Behaviour and survival patterns observed at the lower application rate tested were similar to those from the full-rate tests. Experiments were carried out to investigate behavioural responses to the active ingredients and carrier formulations in isolation. Responses to the insecticides' active ingredients demonstrated that in most cases, the carrier formulation was responsible for the locomotor patterns observed with the products. Although in some cases the opposite was true and the active ingredients elicited responses where the entire products did not, suggesting that the carrier formulation may have inhibited the expression of a response to the active ingredient when testing the entire product. Additionally, C. septempunctata did not demonstrate a preference for treated or untreated substrates, regardless of the treatment applied.en
dc.description.abstractC. septempunctata did not demonstrate preferences for treated or untreated prey when M. persicae were sprayed with insecticides and the coccinellids' consumption rates were recorded (Chapter 4). In these experiments, the pyrethroids again drew the greatest response from C. septempunctata, reducing consumption by the largest amount, whereas the organophosphates led to the greatest mortality. The consistency with the results from Chapter 3 was further reinforced in Chapter 4 by the absence of a response to Aphox-treated prey. Spectrophotometric experiments were conducted using coloured dye to investigate the evenness of spray distribution and deposition provided by the equipment used in Chapter 4. These experiments also enabled the amount of spray collected by each aphid to be quantified.en
dc.description.abstractTo investigate how insecticides are detected in C. septempunctata, scanning electron microscopy (SEM) was used to conduct a morphological study of the palpi and tarsi (Chapter 5). This was followed by an electrophysiological study on the maxillary palps and a study of the coccinellids responses to olfactory stimuli from the insecticides (Chapters 5, 6). The SEM study identified a hitherto unrecorded type of sensilla on the labial palps and biometric analysis extended the level of sexual dimorphism known for this species. Importantly for this study, no chemosensilla were found on the tarsi and with three times more chemosensilla than any other sense organ, the most likely organ responsible for insecticide detection in C. septempunctata was the maxillary palps. The maxillary palps are thought to be involved principally in contact chemoreception, and detection of Dimethoate was confirmed using electrophysiological techniques. The positive neurological response to both the product and the blank formulation (Chapter 5), coupled with the absence of a behavioural response to the insecticide odours (Chapter 6) and the presence of behavioural responses to treated substrates (Chapters 3, 6), provide further evidence that contact chemoreception plays a major role in insecticide detection in C. septempunctata.en
dc.publisherThe University of Edinburghen
dc.relation.isreferencedbyAlready catalogueden
dc.subjectAnnexe Thesis Digitisation Project 2018 Block 18en
dc.titleBehaviour and physiology of the seven-spotted ladybird, Coccinella septempunctata, in response to insecticidesen
dc.typeThesis or Dissertationen
dc.type.qualificationlevelDoctoralen
dc.type.qualificationnamePhD Doctor of Philosophyen


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